[Paleopsych] H-N: Nigel Barber: Evolutionary Explanations for Societal Differences in Single Parenthood
checker at panix.com
Wed Jul 20 19:55:04 UTC 2005
Nigel Barber: Evolutionary Explanations for Societal Differences in Single
[Thanks to Laird for this.]
Evolutionary Psychology 3: 142-174
Evolutionary Explanations for Societal Differences in Single
Nigel Barber, Ph.D.,70 Kent Street, Portland, ME 04102, USA.
The new research strategy presented in this paper, Evolutionary Social
Science, is designed to bridge the gap between evolutionary psychology
that operates from the evolutionary past and social science that is
bounded by recent history. Its core assumptions are (1) that modern
societies owe their character to an interaction of hunter-gatherer
adaptations with the modern environment; (2) that changes in societies
may reflect change in individuals; (3) that historical changes and
cross-societal differences are due to the same adaptational
mechanisms, and (4) that different social contexts (e.g., social
status) modify psychological development through adaptive mechanisms.
Preliminary research is reviewed concerning historical, societal, and
cross-national variation in single parenthood as an illustration of
the potential usefulness of this new approach. Its success at
synthesizing the evidence demonstrates that the time frames of
evolutionary explanation and recent history can be bridged.
: Evolutionary Social Science; Evolutionary Psychology; Single
Parenthood; Societal Differences; Historical Change; Adaptive
Development; Sexual Development; Poverty; Values; Cultural Relativism;
Evolutionary psychology (EP) focuses on human adaptations to the
hunter-gatherer way of life that is believed to have shaped human
psychology over approximately two million years (Barkow, Cosmides, and
Tooby, 1992; Buss, 1999; Cosmides, and Tooby, 1987; Durrant and Ellis,
2003). This approach generally identifies evolutionary influences on
modern behavior in terms of cross-cultural universals such as proposed
universal sex differences in sexual jealousy and mate selection
criteria (Geary, 1998) but recognizes that universal human
characteristics, such as emotions, may find different expression in
different societies (Fessler, 2004). It sees social sciences as
falling within the natural sciences. By contrast, "standard" social
science focuses on the present and attempts to account for behavioral
variation in terms of contemporary influences without reference to the
evolutionary past (Lopreato, and Crippen, 1999).
Although the strategy of identifying universals at the level of
information processing mechanisms of the brain was an important point
of departure in the emergence of evolutionary psychology, this
approach requires elaboration if it is to account for variation in
modern behavior. Just as the social sciences are stuck in the present,
so to speak, evolutionary psychology is focused on the evolutionary
past. Admittedly many evolutionary psychologists have wrestled with
the problem of how one gets from evolved psychology to modern behavior
using constructs that include cognitive modules, Darwinian algorithms,
memes, and so forth (Barkow, Cosmides, and Tooby, 1992). The new
research strategy of evolutionary social science (ESS, Barber, 2005)
strives to overcome the temporal problem (i.e., bridging the
evolutionary past and the present) by using concepts of evolutionary
adaptation to account for variation in modern behavior whether between
siblings, between families, or between societies. This paper employs
the new research strategy to organize data concerning single
parenthood in a way that can stimulate new research.
Before analyzing societal variation in single parenthood, it must be
acknowledged that this new approach makes many controversial
assumptions. It would be helpful to make these assumptions explicit
and to explain briefly why they are necessary. The paper then shows
how these assumptions help to organize data concerning single
parenthood in different societies and at various points in history.
The Assumptions of ESS
ESS confronts evolutionary novelties in human social behavior produced
by modern environments and thus aims to unite the evolutionary frame
of explanation used by evolutionary psychologists and others with the
historical time frame of many social sciences. To this end, it is
necessary to make assumptions that have not been made previously, or
at least not in an explicit and systematic way, with the aim of
uniting the time frames of evolution and recent history. Some of these
assumptions are sufficiently complex, problematic, and even counter
intuitive, that they require some elaboration.
Assumption 1: That modern societies owe their character to
an interaction of hunter-gatherer adaptations with modern ecologies
and environments. This assumption is fairly uncontroversial. However,
as previously noted, existing social sciences generally do not connect
modern life with evolutionary adaptations and are quite resistant to
Assumption 2: Changes in societies may be caused by changes within
individuals and they can affect individuals via bottom-up phenomena
rather than via top-down transmission of values or behaviors
. This form of reduction is actively resisted in some social sciences
but it is worth emphasizing that scientific explanations almost always
proceed by accounting for complex events in terms of more elementary
constituents. Thus, the "behavior" of a molecule is always reducible
to the characteristics of the constituent atoms.
A particularly interesting example of individual change mediating
societal differences is the way that sexual liberation of women in a
particular society is related to an adverse marriage market that means
women's individual chances of contracting a favorable marriage is
bleak, so that they must assert themselves in the monetary economy
through paid employment or operation of businesses (Barber, 2002 a,
2004 a; Guttentag, and Secord, 1983). This phenomenon is by no means
recent, cropping up in 14th-century England, and classical Sparta, for
example. To say that social change in such cases is caused by forces
acting at the individual level might seem like a semantic exercise
given that the marriage market difficulties of females is distributed
throughout the society but ESS opts to use individual-level
explanations of social arrangements because these are theoretically
relevant, viable, and scientifically plausible.
Assumption 3: that historical changes and cross-societal differences
are due to similar adaptational mechanisms.
This assumption contradicts the argument of cultural relativism. This
is not to deny that all societies have some unique features, such as
the peculiarities of their language communication system, their forms
of dress, body ornamentation, basketry, pottery design, and so forth.
Rather, the argument is made that to the extent the phenomena are
truly unique, they defy scientific explanation and are thus of minimal
interest to scientists, as opposed to artists, for example. One
practical ramification of Assumption 3 is that historical mechanisms
can be studied indirectly through cross-societal comparisons of
contemporary peoples. To take a simple example, the high fertility of
women in Africa today is due to the same agricultural mode of
production that supported the majority of American women a century
ago, and was associated with high fertility for them also.
Assumption 4: that different social contexts (e.g., social status)
modify psychological development through adaptive mechanisms
. This can be considered a general theory of psychological development
that not only accounts for the adaptive match between individual
behavior and the social environment, but also helps to explain
historical, and cross-national societal differences. This assumption
can be rephrased as an expectation that certain social inputs during
development shall produce specific behavioral/psychological outcomes.
For example, corporal punishment increases interpersonal aggression,
helping to explain why parents in warlike societies are more likely to
use harsh disciplinary tactics on their sons (Ember and Ember, 1994).
Similarly, there is evidence that reproductive behavior, including
single parenthood, is affected by childhood stressors.
Childhood Stress, Divorce, and the Development of Reproductive
Psychological stress in childhood influences adult sexual psychology
and behavior in part because it alters brain development. Poverty is
one example of a complex stressor in modern societies and researchers
recently discovered that childhood stress alters brain structures and
thus potentially modifies the sexual psychology of males and females
(Teicher, Anderson, Polcari, Anderson, and Navalta, 2002). Brain
biology is far from being the complete picture, of course, and
marriage is greatly affected by the availability of suitable partners,
for example. Whatever the underlying mechanisms, men raised in poverty
are less likely to provide, and women are less likely to require, the
emotional commitment and economic support for children that are
characteristic of the marriage contract around the world, so that
single parenthood is correlated with low income within a country.
Poverty is not the only source of childhood stress, of course. If
psychological stress affects sexual development and reproductive
behavior in predictable ways, then other sources of childhood stress
would be expected to have similar consequences for adult sexual
behavior. Parental divorce is an interesting type of childhood
stressor in this context because it is more of a middle-class
experience in the U.S., for example, not because poor people enjoy
stable marriage, but because they are considerably less likely to wed
in the first place (Abrahamson, 1998). Although children of divorced
parents experience a modest decline in living standards, they remain
much better off, on average, than children raised from the beginning
by single mothers (Waite and Gallagher, 2000). This means that divorce
offers a useful window into the effects of psychological stress,
unalloyed with extreme economic deprivation, on the development of
Wallerstein and Blakeslee (1996) concluded that most American children
who experience a bitterly-fought parental divorce suffer lifelong
problems in forming committed sexual relationships. Their conclusion
is supported by the following data on children of divorced parents
Females are approximately 50% more likely to give birth as teens.
They are approximately 48% more likely to divorce themselves (60% for
white women and 35% for white men).
Their marriages may be either highly impulsive (particularly for
females), or delayed due to lack of self-confidence and trust
(particularly for males). About a quarter of children of divorced
parents (24%) never marry compared to one in six (16%) for the general
population, suggesting a lack of trust in intimate relationships.
They suffer from emotional problems (e.g., depression, behavioral
disorders, learning disabilities) at a rate that is two-and-a-half
times that of the general population.
Correcting the divorce rates by the marriage rates, it can be
estimated that children of divorced parents have only about a
one-in-five probability of being stably married, compared to a
two-in-five chance for the general population (assuming a non-divorce
rate of .50 multiplied by a marriage rate of .84). Compelling as such
numerical differences are, they nevertheless minimize the relationship
correlates of parental divorce because they leave out the emotional
pain, anxiety, conflict, and self-doubt, that Wallerstein's informants
described during lengthy interviews in the context of protracted
Even those who contributed to stable marriage statistics were often
far from happy in their union. According to Wallerstein and Blakeslee
(1996), the facade of marital permanence frequently concealed much
discontent. Low expectations, combined with a sense of helplessness,
often kept children of divorced parents in wrenchingly discordant
marriages that more confident individuals might have changed, or
Evidently, conflict and unhappiness in the parental marriage creates
an expectation in children that their own marriages may be discordant,
or fail. Males and females often respond differently to parental
conflict (Barber, 1998 a, b; Wallerstein and Blakeslee, 1996). Young
women may react to parental friction and separation with precocious
sexuality. They initiate sexual activity sooner, and may even reach
sexual maturity earlier, compared to young women raised in intact
marriages (Ellis, 2004; Ellis, Bates, Dodge, Fergus, Horwood, Petit,
et al., 2003). These phenomena help to explain the higher rate of teen
pregnancy and childbearing among children of divorced parents.
Marriages are often early, and impetuous, as well.
In the absence of a reasonable period of courtship in which the couple
get to know each other, and conduct a protracted evaluation process,
marriages are liable to be incompatible, and unstable. Early marriages
are also more likely to end in divorce. While the young women may
enter marriage recklessly, Wallerstein and Blakeslee (1996) describe a
rather different type of commitment problem as characteristic of male
children of divorced parents. These may experience lifelong
difficulties in expressing, or even acknowledging, their emotions,
which impedes sexual relationships and militates against happiness in
a marriage. Many fear intimacy and postpone committed relationships
(Barber, 1998a, b).
Some children may feel so traumatized by parental divorce that they
are inclined to postpone marital commitment (Wallerstein and
Blakeslee, 1996) preferring to cohabit before marriage (Whitehead and
Popenoe, 2002). For individuals who fear marital commitment, this
might seem a sensible way of progressing to a more committed, more
permanent relationship. Informal unions are highly unstable, however,
(Smock, 2000) possibly because of the lack of commitment with which
they begin (Waite and Gallagher, 2000).
Wallerstein and Blakeslee (1996) serve rather like a Greek chorus in
emphasizing the tribulations inflicted on children by parental
divorce. By contrast Hetherington and Kelly (2002), serve as
cheerleaders for children's powers of recovery following parental
divorce. Hetherington collected data on some 1,400 families and their
2,500 children spanning three decades, focusing on objective facts
rather than the more subjective interview techniques employed by
Wallerstein on smaller samples. Hetherington found that the majority
of children are resilient and bounce back from the distress of
parental divorce in a few years without experiencing major behavioral
or emotional problems.
Hetherington's optimistic conclusions are summarized in a Time
magazine interview (Corliss, 2002): "A lot of the current work makes
it sound as if you've given your kids a terminal disease when they go
through a divorce. I am not pro-divorce. I think people should work
harder on their marriages: support each other and weather the rough
spots. And divorce is a painful experience. I've never seen a
victimless divorce - where the mother, father, or child, didn't suffer
extreme distress when the family broke up. But 75% to 80% do recover."
By "recovery" Hetherington means the absence of serious psychological,
social, or emotional problems that would warrant professional
attention. Given that 75% of children "recover" by this definition,
25% experience serious emotional problems, compared to 10% of children
from intact two-parent families. In other words, their risk of serious
emotional problems is more than doubled. In addition to those
individuals with diagnosable psychological problems in the years
immediately following parental divorce, many others could have serious
lifelong problems in forming happy and committed reproductive
relationships. These problems are at least partly attributed to the
stress of parental divorce, although other environmental factors, such
as social learning and inadequate opportunities to acquire social
skills cannot be ruled out.
Genetic influences may also matter. This point is most clearly
established in research finding an association of the androgen
receptor gene with aggression, impulsivity, and number of sexual
partners, and parental divorce for both sexes as well as female age of
menarche (Comings, Muhleman, Johnson, and MacMurray, 2002), although
the effect sizes were modest. Yet, the problems of children of
divorced parents are not just a product of inheriting "hostile" or
"emotionally troubled" genes from parents. This conclusion emerges
from behavior genetics research comparing outcomes for adopted
children with those of biological children subsequent to parental
divorce. Adoptees suffer more from emotional problems following
parental divorce even though they share no genes with the divorcing
parents (O'Connor, Caspi, DeFries, and Plomin, 2000). Quinlan's (2003)
analysis of data from the National Survey of Family Growth also found
that parental separation before the age of five years predicted early
menarche, age of first pregnancy, and shorter duration of first
marriage. Parental separation during adolescence was more strongly
predictive of number of sex partners, however, suggesting that changes
in care-taking arrangements have complex age-dependent effects on the
development of sexual and reproductive behavior. If the stress of
parental divorce and/or separation can have substantial effects on
marital commitment in the second generation, it is not hard to imagine
that the multiple stresses of poverty could have comparable effects on
sexual behavior and marriage (see below).
In summary, a stressful early childhood increases the probability of
single parenthood because of the resulting difficulty in forming
committed reproductive relationships. This is true of parental
conflict surrounding divorce, but it may also be linked to childhood
poverty, or other causes, thus implicating developmental changes in
the brain. On the other hand, single parenthood may occur at high
levels in societies where children are exceptionally well off, and do
not have highly stressful childhoods, as is true of Sweden, for
example, pointing to multiple causation.
Nonmarital reproduction is a complex phenomenon that reflects the
reproductive strategies, and sexual behavior, of both sexes. These are
affected in interesting and complex ways by economic influences and
marriage markets, as illustrated by research on the history of single
Poverty and the History of Single Parenthood
Poverty can affect reproductive behavior in two different ways each
suggesting adaptive design: through the effects of stressors on brain
development; and through its effects on marital opportunity. There is
abundant historical evidence that poverty was an important influence
on single parenthood because of its limiting effects on marital
opportunity due to scarcity of men who were economically qualified for
marriage. Even today, depressed economic conditions around the world,
and high male unemployment, occur in nations that have high ratios of
nonmarital births (Barber, 2003 c). Historical evidence indicates that
the reproductive practices of young people in respect to nonmarital
childbearing were affected by economic circumstances (Abrahamson,
Economic determinism is not the only possible explanation for
historically changing single parenthood ratios, of course. Many social
historians, believe that changes in single parenthood ratios are due
to changing degrees of sexual liberation. Thus, the steady rise in
single parenthood ratios for many European countries throughout much
of the 19th century is attributed to increasing sexual liberation
associated with industrialization of the economy and urbanization of
the population. There is little doubt that changes in single
parenthood ratios of this period were genuinely connected to the
ongoing Industrial Revolution but appealing to sexual liberation as
the cause falls short as a scientific explanation, particularly
failing to explain historical changes in sexual attitudes, as
explained in more detail below.
The increase in single parenthood during the 19th-century period of
industrialization may be illustrated by the case of France where
single parenthood ratios rose from about 5% of all births at the
beginning of the century to about 10% at its end (Shorter, 1975). The
largest increase in single parenthood occurred in cities, such as
Paris and Bordeaux, where illegitimacy ratios surged above 30%,
comparable to the level seen in many modern cities. Other European
cities manifested a similar rise in single parenthood, partly
reflecting an increase in the number of young single women who
migrated to cities and towns in response to job opportunities
associated with urban development following the Industrial Revolution.
There are many reasons why urbanization may increase single
parenthood. Thus, living in an unfamiliar social environment, young
women may have experienced difficulty in finding husbands. This
problem was exacerbated by an excess of single women to single men
(because young males were more likely to remain at home to work on
family farms). The same phenomenon is still in evidence in modern
cities where the feminine population generally exceeds the masculine
one (Guttentag and Secord, 1983). Thus, for U.S. metropolitan areas,
there are just 93 males over the age of 16 years per 100 females when
people living in prisons, and other institutions, are excluded
European single parenthood ratios increased during the 19th century,
until about 1880, when a decline began that lasted for over two
decades (Shorter, 1975). This decline was accompanied by a decrease in
marital fertility, and both phenomena evidently reflect use of
condoms, or other contraceptive devices, that became widespread about
this time (Langford, 1991).
The sharp and widespread increase in single parenthood following the
industrial revolution is apparently without historical precedent and
thus a challenge for historians as well as ESS. Many historians see
increased single parenthood as a product of sexual liberation (or
moral degeneration, depending on their perspective).
According to the sexual liberation argument, urbanization brought
large numbers of lustful young men and women together in an
environment where the watchful eyes of relatives, and other
traditional constraints on sexual behavior no longer mattered. They
converted newfound sexual opportunity into sexual expression outside
marriage thereby boosting illegitimate births.
The sexual liberation interpretation may well describe changing
patterns of sexual behavior but it is far from satisfying when judged
by the criteria of a scientific explanation for those changes. One
problem is circularity. Sexual liberation is defined by an increased
probability of sex outside marriage. For much of the 19th century,
prior to widespread use of contraceptives, increased extramarital
sexuality produced an inevitable rise in single parenthood. (It is
true that premarital conceptions could be, and often were,
legitimized, by marriage, however). If such complications are set
aside, attributing increased ratios of single parenthood to sexual
liberation is largely an exercise in circular reasoning. If we did not
have data on single parenthood, we might not know that sexual behavior
was "liberated." Other clues of such trends may be uncovered by
historians, of course, including explicit depictions of sexual
behavior in the arts and literature, or an increase in tax revenues
from prostitution, but such measures of sexual liberation often lack
the consistency and validity of the illegitimacy ratio itself.
Strictly speaking, scientific explanation requires that the
explanatory variable be measured independently of what is being
explained, a criterion that is often lacking in social research. Yet,
it is disputable whether sexual liberation can be reliably measured in
historical research without referring to the illegitimacy ratio. If
sexual liberation cannot be separated from single parenthood, then one
phenomenon cannot be used as a scientific explanation of the other:
they are not independent. Explaining one in terms of the other is thus
an exercise in circular reasoning.
Even if sexual liberation could be measured independently of
premarital sexuality, there is still a problem about direction of
causation between attitudes and behavior. Do sexually liberated
attitudes cause sexually liberated behavior, or do attitudes conform
to behavior? A large technical literature on the connection between
sexual attitudes and behavior suggests that both directions of
causation might apply (Moors, 2000). Young women who cohabit become
more sexually liberated in their attitudes following this experience,
for example. Such evidence once again highlights the difficulty of
establishing scientific independence between attitudes of sexual
liberation and sexually liberated behavior.
The sexual liberation hypothesis of increasing single parenthood with
urbanization is not a genuine explanation: it does not provide a
causal explanation for this historical change. Even if one admits that
female residents of Paris produced 30% of their offspring outside
wedlock in 1880 due to sexual liberation, this does not solve the
fundamental problem of why Parisiennes were so much less liberated a
century earlier when nonmarital birth ratios were below 5%.
Sexual liberation interpretations may deflect attention away from the
real drivers of historical change, of which economic factors seem
particularly important. The influence of economic constraints on
family formation is well illustrated by English historical research
dealing with local increases in nonmarital birth ratios (Abrahamson,
Historical "Outbreaks" of Single Parenthood in English Communities
Single parenthood is rarely even mentioned by anthropologists,
suggesting that it would have been difficult for women in the
evolutionary past to raise children alone. Similarly, throughout the
era of written history, single parenthood was not a practical
alternative and was chosen only as a last resort by women who failed
to marry. In addition to the economic difficulties of single
parenthood, illegitimate children were at a real social disadvantage
in England. They were stigmatized, or ostracized, and suffered real
legal disadvantages in the sense of not being able to inherit
property, for example. The great majority of English women, typically
in excess of 95%, were married when they gave birth, suggesting that
the minority of single mothers were victims of ill fortune due to
unintended pregnancy combined with an inability to demand marriage
from the father (Shorter, 1975).
In such a social environment, women raised children alone only for
lack of a better alternative. Marriage prospects were severely
curtailed by economic problems. This phenomenon is illustrated in
English history, where crop failures forced couples to delay marriage
because they lacked the economic resources to set up an independent
household. If they were sexually active before marriage, this meant
they were at greater risk of producing out-of-wedlock births.
When Abrahamson (2000) examined historical surges in local
out-of-wedlock birth ratios in England between 1590 and 1985, he found
that all eleven cases of high nonmarital birth ratios followed an
economic downturn. This phenomenon may be illustrated by the case of
Terling, a small agricultural community 30 miles northeast of London.
Between 1560 and 1590, nonmarital births were low, even by historical
standards, constituting between 1% and 2% of total births. The
illegitimacy ratio rose between 1590 and 1605, when it reached 10%.
Abrahamson attributes this increase to an economic phenomenon that is
familiar from more recent periods, namely price inflation.
Terling's economic problems began in the 1580s and can be traced to
population growth. With more mouths to feed, and an increased demand
for food, prices soared. Price inflation eroded the purchasing power
of wages, making it difficult for the landless poor, to make ends
meet. This bad food scarcity was aggravated by a series of crop
failures during the 1590s. The worsening economic situation made it
economically impossible for many young couples to marry, and set up
households, even if the woman was pregnant.
Being an unmarried mother invited legal sanctions and pregnant women
could be punished, for immorality, or "fornication." At the peak of
the illegitimacy "outbreak," legal enforcement was comparatively lax.
Only a third of unmarried pregnant women were prosecuted, compared to
three-quarters of them in more normal times. Many women were excused
prosecution on the understanding that they would marry when their
fortunes improved. This comparative leniency evidently reflected some
understanding that marriage was constrained by difficult economic
circumstances. When the economy improved, fornication laws were
enforced more rigidly again. A similar change occurred in respect to
enforcement of prostitution laws. In the difficult period after 1590,
when few young men were marrying, and the services of prostitutes were
in high demand, enforcement of vice laws was also relaxed, providing
further evidence of the plasticity of moral, and legal, codes in the
face of changing economic conditions (Abrahamson, 2000).
The constraints faced by young women in 16th-century England are
obviously very different from the situation of modern women. The use
of effective birth control, for example, means that single women are
quite unlikely to become pregnant as a result of delayed marriage
today. Even so, economic conditions affect the marriage market and
single parenthood ratios of the 20th century in complex ways. This
phenomenon has often been highlighted in connection with the marriage
difficulties of African American women, for example.
African American scholars, including Wilson (1997), emphasize the
impact of declining job prospects for African American men on single
parenthood. He points to the decline in well-paid blue-collar
manufacturing jobs in the U.S. after about 1950. Many African American
men were subsequently forced into poorly-paid dead-end service jobs
that provided little chance of supporting a family. According to
Wilson, this meant that a large proportion of African American men
were economically disqualified from marriage. The scarcity of men who
were economically qualified for marriage was exacerbated by a host of
other factors, reducing the availability of men for marriage. They
included: low sex ratios at birth, higher mortality of young men,
marriage of more black males than females outside their ethnic group,
and high rates of incarceration in prisons. In 1950, for example,
there were approximately 70 employed men aged 20-24 years per 100
same-aged women (Staples, 1985). Thirty years later, in 1980, there
were only, 50 marriageable men per 100 women in this age category.
Other research supports the hypothesis that reduced marriage
opportunities of African American women play an important role in
accounting for their high single parenthood ratios. Thus, African
Americans living in metropolitan areas where there is a scarcity of
marriageable men have higher ratios of single parenthood (Fossett, and
Kiecolt, 1991). Based on state-level data, South and Lloyd (1992)
found that ratios of nonmarital births decline with increases in
availability of marriageable men (as indexed by the sex ratio). South
(1996) found, however, that although young women were more likely to
marry as the availability of males increased, increases in the
proportion of males in high schools increased the chances of single
parenthood, a puzzling result that is inconsistent with the rest of
the literature. Births to African American teens (the great majority
of which are to single mothers) were also predictable from reduced
mate availability according to research comparing U.S. metropolitan
areas (Barber, 2002b) and states (Barber, 2002c) in analyses that
controlled for poverty and unemployment.
The same economic principles thus help explain why single parenthood
was common among 20th-century African Americans as well as 16th
century farmers in England. A similar logic applies to poor
20th-century European Americans also. In some economically depressed
White neighborhoods, including the lower end of South Boston the
majority of children are born outside marriage (73% in 1990, Whitman,
1996). Where there is a severe scarcity of marriageable men, (which is
more likely in poor communities), women must choose between raising
their children outside marriage or forgoing reproduction altogether.
The marriage market, and the economic variables affecting it thus
provides a good understanding of historical changes in single
parenthood. This conclusion is also supported in time series analysis
of single parenthood in England, Scotland, and the U.S. (Barber, 2004
a). A similar pattern emerges from cross-national studies, as well as
comparisons among U.S. states and metropolitan areas (Barber, 2000 a,
2000 b, 2001, 2002 a) that controlled for numerous variables such as
female literacy, contraception use, poverty, unemployment,
incarceration rates, and so forth. Whatever unit of analysis, or time
period, is studied, the data are consistent in showing that young
women who face a scarcity of marriageable men are more likely to begin
their reproductive careers early in life and to raise their children
with minimal paternal investment, consistent with the anthropological
conclusion that if men cannot be relied upon to provide long term
parental investment women gravitate to earlier reproduction (Draper
and Harpending, 1982).
The data on single parenthood are thus consistent with assumption 3,
stating that historical changes and societal differences are due to
the same mechanisms. Of course, these data do not guarantee such
uniformity for other areas of study but they do at suggest that ESS is
a workable research strategy.
Environmental influences on reproductive strategies do not end with
the marriage market, of course. Within a society, or community,
particular individuals are more or less likely to form long-term,
committed, romantic relationships depending, in part, on their
childhood experiences, including the stresses of poverty (or parental
divorce). This phenomenon thus provides a concrete example of
Assumption 4 -- that different social contexts modify psychological
Poverty and the Emotional Basis of Single Parenthood
There is no doubt that economic disadvantage impaired marriage
formation over many centuries of European history. A crucial question
to ask in this connection is whether individuals make adaptive
emotional adjustments that allow them to fit in with an environment of
reduced marital opportunity for either sex. Perhaps surprisingly,
there is fairly good evidence that the emotional development of the
individual is modified in ways that help her, or him, to fit in with
economic, and romantic, limitations of the local environment.
To begin with, one finds that the emotional tone of low-income
households is very different from that of more affluent ones. Poverty
is accompanied by greater emotional negativity in the home as revealed
by research on content analysis of speech, problem-solving by
children, child abuse, antisocial behavior, mental illness, and so on
(Barber, 2002 a; Hart and Risley, 1995]. Exposure to negative
emotionality in early life evidently reduces trust, and commitment, in
future relationships, particularly intimate ones, like close
friendships and marriage (Belsky, Steinberg, and Draper, 1991). If
poor children experience more emotional negativity in early life, does
this mean that they have greater difficulty in establishing the trust
required for stable reproductive relationships? Is poverty within a
society a useful predictor of individual differences in emotional
One way of assessing this question is to investigate the effects of
parental income on single parenthood ratios in cross-sectional
research. If women are raised in poverty are they more likely to
reproduce as single mothers, all else being equal?
Based on the theoretical perspective of Belsky, et al., (1991) and
assuming that poverty is psychologically stressful (Lupien, King,
Meaney, and McEwen, 2001), one would predict that poverty should evoke
emotional negativity during childhood, thereby increasing subsequent
emotional commitment problems, so that people raised in poverty would
be more likely to be single parents.
Poverty can be measured indirectly in terms of low educational
attainment given that education affects a person's earning potential
in our society. Low education level is a powerful predictor of single
parenthood. Using education level as a proxy measure, it turns out
that poor women are considerably more likely to have out-of wedlock
births. According to U.S. data for 1994, 46% of the children born to
female high school dropouts were outside wedlock, as opposed to just
6% of children born to women with a bachelor's degree. (Respective
proportions for high school graduates and women with some college were
30% and 17% respectively Abrahamson, 1998). Similar patterns apply to
single fathers. These results suggest a remarkable bifurcation in
American society whereby affluent, well-educated, women maintain
single parenthood ratios that are not appreciably different from
historical norms whereas poor women demonstrate a huge increase in
single parenthood, consistent with the emotional development thesis.
Of course, poor women are also more likely to raise children alone
because they encounter fewer men in their social circles who are
economically qualified as marriage partners.
Although historical research on single parenthood emphasizes the
economic characteristics of males, the greater participation of modern
women in paid labor means that their own economic opportunities are an
increasingly important influence on family structure. Broadly
speaking, there are two distinct subtypes of feminine economic
independence. Close to the top of the economic hierarchy, women have
the option of raising children independently, although this option is
less desirable in some countries than others for various economic and
political reasons, such as government contributions to child support.
"Murphy Browns" are thin on the ground in the U.S., for example but
evidently much more common in social democratic countries like Sweden.
Closer to the bottom of the economic hierarchy, poor women may be
independent of paternal support of children by necessity, i.e., there
is a scarcity of economically qualified men.
As these notions imply, wealthy women are more likely to begin their
careers as single mothers comparatively late in life, after they have
established themselves in careers, (which typically takes some ten
years of effort; Goldin, 1995; Kaplan, Lancaster, Tucker, and
Anderson, 2002), whereas poor women are more likely to begin their
reproductive careers as single mothers earlier in life.
Interestingly, a young woman's career prospects can have a major
influence on when she begins her family. One of the best measures of
career potential is academic success in high school and academic
failure greatly increases the probability of single teen childbearing.
Data from the National longitudinal Study of Youth indicate that women
aged 15-19 yr at the bottom fifth of their high school class in math
and reading skills are five times more likely to bear children
compared to those in the top fifth (15% compared to 3% per year,
Pittman and Govan, 1986). Although most teen pregnancies are
unplanned, career motivation affects deliberate reproductive choices
in predictable ways. Thus, when teens having high career aspirations
find themselves pregnant, they are more likely to have an abortion.
Young women with low career aspirations are more strongly motivated to
invest their time and energy in raising a child (Barber, 2000 a,
Pittman and Govan, 1986).
Despite efforts in many social democratic countries of Europe to ease
conflicts between work and family, there is often a clash between
raising children and developing a career. This conflict may be deduced
from the fact that career women postpone reproduction for
approximately a decade compared to those without careers (defined as
earnings above the lowest 25%, Goldin, 1995).
The conflict between careers and early reproduction is thus fairly
straightforward and can be thought of as partly a product of
conflicting time demands between career and family. The connection
between educational failure and early reproduction of single women is
rather more complex.
To begin with, sub par educational performance predisposes young
women, particularly poor ones, to early sexuality for a variety of
reasons. Early single parenthood is facilitated not just because of
bad career prospects but also by diminished opportunities for
The role of poverty in diminished marriage prospects may be
illustrated by comparing various U.S. ethnic groups that differ in
average earnings. One measure of marriage difficulty is the proportion
of women who reach the end of their reproductive lives without
marrying. By the age of 40-44 years, 22% of African American women
have never married, compared to just 7% of whites and 10% of Hispanics
(Abrahamson, 1998). The poorer groups, (African Americans and
Hispanics), thus have substantially higher rates of non marriage
compared to Whites. These data constitute a very conservative measure
of marriage problems among poor women, however. Thus, although the
great majority of Black women eventually marry, they are likely to be
unmarried when their first child is born and spend much of their peak
reproductive years as single mothers due to delayed marriage and to
Data on first births before marriage provide a clearer picture of the
marriage market difficulties of poorer U.S. ethnic groups. Between
1990 and 1994, three quarters of African American first births were
before marriage compared to two-fifths for Hispanics, and a quarter
for whites (Abrahamson, 1998). Women from poorer ethnic groups are
thus considerably less likely to marry before giving birth for the
first time. Note that African American women are considerably more
likely to be single at the time of their first birth compared to
Hispanics although there are minimal differences in income, that
actually favored African Americans at this period. These differences
probably reflect the scarcity of young males in African American
communities due to early deaths, illnesses, accidents, and
incarceration, among other factors (Barber, 2002a).
In addition to the adaptive pattern of relationships between single
parenthood and economic factors (including the marriage market)
children raised in poverty generally experience a psychologically
harsher early life that militates against the trust, commitment, and
empathy, that form the basis of successful marriages (see below).
Alternatively stated, in an environment where marriage is less viable
as a reproductive strategy, children mature with less interest in, or
potential for, stable romantic relationships. This suggests that
children are raised to fit in with the practical realities of adult
life in their particular community. In other words, it suggests
adaptive flexibility in the development of human sexual behavior.
Further evidence for this interpretation is provided by research on
the development of sexual behavior as a function of parental income.
Poverty and Adaptive Flexibility in Sexual Development
One way in which poverty affects single parenthood is clearly through
the limitations it places on marriage formation, as illustrated both
by historical and contemporary research using various methodologies.
Sexologists have long been aware of differences in sexual behavior as
a function of socioeconomic status and it seems reasonable to classify
such differences as manifestations of a more general phenomenon of
adaptive flexibility in sexual development. Generally speaking, being
raised in poverty predisposes men to short-term relationships, or the
low-investing "cad" strategy described by evolutionary psychologists
(as opposed to the high-investing "dad" strategy, (Cashdan, 1993;
Draper and Harpending, 1982). Men would not succeed in their career as
cads if this were not tolerated, or even encouraged, by women having a
similarly short-term perspective on sexual relationships, however.
This argument is clearly supported by anthropologist Elizabeth
Cashdan's (1993) research on sexual strategies of college students.
She found that women's and men's sexual behavior varies considerably
as a function of their expectations about masculine commitment in
sexual relationships. Cashdan concluded that the less emotional
commitment women expected from men in their dating pool, the more
short-term their own perspective was. Women who believed that their
dating environment was full of cads, dressed provocatively, and had
many sexual partners. On the other hand, if they encountered many
potential dads, i.e., caring and nurturing men, they behaved more
sedately, emphasizing their own propensities for sexual fidelity and
chastity. Cashdan reported that cads attracted women by drawing
attention to their physical appearance, and sexuality, whereas dads
"advertised" their economic assets, or capacity for economic success,
as well as their desire for a permanent relationship. While some
readers might see such findings as confirming outmoded stereotypes of
sex differences in sexual behavior, it is important to recognize that
college students, as a group, are arguably more immune from
preconceived notions about sexual behavior than other segments of the
population and are thus expressing evolved psychological propensities
within this particular environment (see Townsend, 1998, for a similar
argument concerning medical students).
While young college students adapt their dating behavior to the
immediate social environment, it is quite clear that some of the
variation in sexual behavior is also affected by the developmental
environment (as well as genetically inherited variation, Simpson and
Gangestad, 1992). Thus, a more stressful early environment predisposes
people to short-term, or unstable, sexual relationships, as manifested
by the data on children of divorced parents, for example. Other
complex childhood stressors, specifically poverty, may have similar
Most theories of the influence of stressful home environments on the
development of sexual behavior emphasize the pathological aspects, as
reflected in social problems like school failure, delinquency, and so
forth. Evolutionists are more willing to accept that there is a range
of adaptive variation, and that children's responses to stressful
rearing experiences may constitute normal function in an adverse
environment rather than the breakdown of normal developmental
To this end, Belsky, et al. (1991), proposed that children who
experience insensitive parenting, which is more characteristic of
low-income homes, are better prepared to prosper in a harshly
competitive adult social environment. Belsky et al.'s evolutionary
theory of socialization pivots on the principle that unresponsive
parenting elicits exploitative interpersonal attitudes and antisocial
behavior in the second generation. It also produces a short-term
perspective towards sexuality.
Given that poverty is associated with increased psychological stress
among children, it would be predicted to have all of the above
effects. The most compelling evidence of emotional negativity in
parent-child relationships in poor homes comes from analysis of actual
speech content addressed to children in economically disadvantaged
homes. Parents provide far less verbal stimulation to children in poor
homes, which has important implications for cognitive development in
general, and for the development of vocabulary size in particular.
Poor parents say much less to their children and what they do say is
much likely to have a hostile, emotionally negative, or disparaging,
tone, to involve scolding rather than praise (Hart, and Risley, 1995).
The implied relative lack of emotional warmth between parents and
children has rather obvious implications for future sexual
Thus, poor single teenage mothers often complain about a lack of
warmth in relations with mothers according to Musick (1993). Research
on the home backgrounds of single teen mothers finds that they
experience many psychological stresses, and sources of negative
emotionality, when compared to non mothers (Corona, and Tidwell,
1999). Family problems included: the absence of a father figure to
provide emotional and economic support; arguments between parents;
exposure to drug addiction or alcoholism in the home; parental
divorce; physical, sexual, or emotional abuse; and unsatisfactory or
unstable relationships with foster homes.
Separation from fathers (which occurs more commonly in low-income
homes) may engender a sense of emotional deprivation for which early
sexual relationships seem to provide an answer. The likelihood of
young women being sexually active at an early age, and becoming
pregnant in teenage years, is increased by a perceived lack of
emotional closeness to their mothers. Many teen mothers describe the
relationship with their own mothers as both difficult and distant in
interview studies. Some of the mothers are emotionally rejecting and
others emotionally dependent on their daughters (Corona, and Tidwell,
1999}. Psychologists find that father absence does not have the same
consequences where it is due to bereavement, suggesting a complex
interaction of factors in the family environment on emotional
development (Barber, 2000 a; Popenoe, 1996).
Unsatisfying emotional relationships with parents may produce complex
effects on sexual psychology. Many young single mothers have
conflicting attitudes to men. Perhaps, consistent with what they may
have witnessed around their own homes, they view most men as
unreliable, alcoholic, and potentially violent. Conversely, they may
entertain unrealistically favorable expectations of their own
partners, hoping that once they become pregnant, their boyfriend will
fall in love with them and propose marriage. Anderson (1990) paints a
vivid picture of the short-term sexual relationships conducted by
young African American mothers inhabiting economically depressed inner
cities where marriage prospects are diminished by unfavorable economic
conditions as well as the scarcity of men. Anderson describes dating
in this environment as an odd mixture of calculation and vulnerability
wherein young women use their sexuality to manipulate men and often
end up pregnant and abandoned. His "streetwise" young men are
portrayed as befriending women purely to obtain sexual gratification
that they refer to as "hit and run" or "booty." To accomplish their
short-term sexual goals, men cater to female fantasies by offering
extravagant, if insincere, promises of affection, love, and even
marriage. After a young woman finds herself pregnant, she is likely to
be abandoned, with contempt. The relationship ends and the cycle
begins anew with a different partner. Playing their role as cads to
perfection, the "streetwise" man refuses to support the children he
has fathered. Where women perceive their world to be full of cads,
they also employ short-term reproductive tactics, emphasizing their
physical attractiveness and using their sexuality as a bargaining chip
to obtain the attention and fleeting affections of men (Cashdan,
Short-term reproductive strategies are clearly not peculiar to
America's inner city but can be seen as an adaptive response to
difficult economic circumstances in any country. Sex researchers
working in the U.S., and Britain, found that working class people, or
low-income people, were generally more unrestrained in their sexual
attitudes and behavior compared to the rest of the population. During
the 1960's, middle class youth tended to catch up with their working
class counterparts in terms of premarital sexuality, and other
measures of sexuality, however. English research conducted in the
1960s and 1970s nonetheless found that income-group differences
persisted in the sense that working class youth were sexually active
from an earlier age. (Argyle, 1994)
Eysenck (1976), reported that working class Britons were more likely
to approve of marital infidelity and to agree that physical
gratification is the most important aspect of marriage. He concluded
that working class respondents to surveys are more earthy whereas
middle class respondents are more moral in their sexual attitudes.
Eysenck believed that working class people had more libido. American
research conducted at the end of the 1980s reached similar
conclusions, finding that college-educated people to be more
restrained than others in a wide variety of sexual behaviors.
Ironically, poorer people are less satisfied with marital sexuality,
(even though they report having sex somewhat more often). They are
more likely to have extramarital relationships (at least for men,
Recent research suggests that the more short-term sexual orientation
of poor people might be attributable to the effects of stress on the
developing brain. Among victims of child abuse (psychological as well
as physical), for example, early stress alters brain anatomy and
function thereby producing a pattern of high sex drive and low sexual
satisfaction (Teicher, et al., 2002). Considered as a complex
stressor, poverty could have the same type of effect especially
considering that stress is a psychological phenomenon that may be
produced in emotionally negative homes where no threshold of criminal
abuse is passed (Teicher, et al. 2002).
Short-term physical relationships are not restricted to the poor, of
course. They are conducted by affluent young people on American
college campuses, as depicted, for example, in Townsend's (1998) study
of sexual relationships among medical school students. His female
informants described dozens of sexual relationships, many undertaken
for the most trivial of motives. Some women slept with physically
attractive men primarily to demonstrate their own sexual desirability.
Jilted women occasionally made love with their former lover's best
friend motivated solely by spite. Shallow, or even malicious, sexual
relationships are clearly not restricted to poor men.
The association between poverty and the development of relatively
unrestricted sexual behavior of both men and women helps to explain
why single parenthood is more common in poor neighborhoods. This
implies adaptations of sexual psychology to varied landscapes of
economic opportunity. In some cases, these phenomena are quite well
understood in terms of psychological development and recent research
has begun to pinpoint possible underlying brain mechanisms (Teicher,
et al., 2002).
Short-term reproductive strategies of men are quite easily
accommodated within an evolutionary perspective because they confer
increased reproductive success on cads, thus ensuring that a
willingness for uncommitted sexual relationships would be promoted by
natural selection (Symons, 1979). Why are single mothers willing to
accept reduced paternal investment in their offspring?
Why Women Accept Reduced Paternal Investment
A comprehensive analysis of historical and evolutionary factors
affecting single parenthood is not possible without some understanding
of the dynamics of marriage markets and their influence on sexual
behavior. This sort of analysis was pioneered by Guttentag and Secord
(1983). Their cross-cultural and historical comparisons demonstrated
that a scarcity of men in the population is generally correlated with
"liberated" sexual behavior as women compete for a diminished pool of
young men by emphasizing their sexual availability. The scarcity of
men in ancient Sparta, due partly to the practice of male infanticide,
and to warfare, was used to explain the sexual liberation of women
there, for example, whereas the excess of males in contemporary Athens
accounted for the extreme preoccupation with feminine chastity in that
Similarly, Guttentag and Secord's (1983) historical analysis of sexual
behavior in the U.S. concluded that a more difficult marriage market
faced by young women in the 1960s compared to the 1950s liberated
women's sexual behavior, as more women began having intercourse before
marriage, and dressed provocatively suggesting sexual availability.
Changing sexual behavior can thus be accounted for in terms of
changing marriage market dynamics.
A scarcity of men, means that some women will inevitably fail to marry
and are therefore liable to become sexually active outside marriage.
The presence of a pool of sexually active single women essentially
sets up an "arms race" whereby women who are interested in marriage
must offer pre-marital sexual activity to compete for masculine
attention and affection. This is in marked contrast to the coy
strategy prevailing in societies where women's marriage prospects are
very good and where they advertise chastity as a means of ensuring
paternity confidence that is universally desirable for prospective
husbands (Barber, 2002a, Symons, 1979). In sexually liberated
societies, women thus play a very delicate game of implying that they
are ready for sexual intercourse with their boyfriend, while
simultaneously denying that are the sort of woman who enjoys many sex
partners and is thus undesirable as a wife who provides low confidence
of paternity in relation to children of the marriage (Symons, 1979).
Such marriage market dynamics are particularly influential in the
lives of poor women. For them, the supply of marriageable males is
particularly bleak, as already discussed. There is thus a large pool
of sexually active single women in low-income neighborhoods, which
favors a cad strategy that seems to be particularly common in that
environment. The prevalence of short-term reproductive strategies
means that both males and females are likely to be sexually active
from an early age. (Indeed a women's sexual maturation can be
accelerated by a few months by a stressful early environment such as
that characteristic of poverty and father absence, Ellis, et al.
2003). A plentiful supply of sexually active single young women favors
an opportunistic strategy by young men who can achieve sexual
gratification without providing any long term emotional commitment, or
paternal investment (in the event of pregnancy).
If poverty makes it difficult for men to support their children, their
reproductive success is favored by pursuing a cad strategy (i.e.,
seeking sexual gratification in short-term relationships) and
emphasizing mating effort rather than paternal investment. This might
be considered the default strategy of male mammals, most of which
invest little in offspring and compete aggressively with other males
for mating opportunities and reproductive success (Geary and Flinn,
2001; Hewlett, 1992). (The word "strategy" is used here in the
technical sense of an evolutionary mechanism, has no connotation of
intentionality, and does not imply that people want to have children -
only that they behave in ways that are liable to increase their
If poor men are less able to provide economic support for their
children, then devoting themselves to mating effort rather than
paternal investment is adaptive, i.e., generally promotes reproductive
success. The cad strategy may work for economically-disadvantaged men.
The real question is why young women should forgo most paternal
investment by opting to raise children alone.
The reasons are complex but the following points should be borne in
Poor women who do poorly at school, have less to lose, socially or
economically, from early childbearing. In fact, bearing a child gives
them a sense of importance and accomplishment that they did not get
from their academic efforts (Barber, 2000a; Musick, 1993).
Young mothers may anticipate a long-term relationship when they become
Fathers of children borne by teenage women are characteristically more
than three years older than the mothers (Landry, and Forrest, 1995).
The father's relative maturity can be flattering to younger women and
means that he tends to be more attractive as well as more controlling.
In addition to gravitating to older men, poor young women evidently
prefer to associate with socially dominant men as well. Thus, gang
leaders are much more sexually active than other gang members and have
more sexual partners (Palmer, and Tilley, 1995). This implies that
women living in poor urban neighborhoods select men on the basis of
qualities associated with social success there, i.e., on the basis of
attributes such as social dominance, ruthlessness, and aggression,
that generally have negative connotations for women in more affluent
neighborhoods. This suggests adaptive design because they are
acquiring for their male offspring qualities associated with
reproductive success in the local environment (Barber, 1995).
The majority of poor single teen mothers have a history of some kind
of childhood sexual abuse (Barber, 2000a; Boyer and Pine, 1992;
Musick, 1993). This has the effect both of advancing the age of
voluntary sexual activity and works against the development of social
skills that would facilitate equity in their sexual relationships.
Looking at the world from a very different perspective, social workers
are inclined to see teenage child-bearing as both self-defeating and
pathological, which it might be in more affluent circumstances. Yet, a
good case can be made that early single parenthood is essentially an
adaptive response to an environment in which there is limited economic
opportunities for women and where they cannot expect much paternal
investment in their children.
In a low-investment environment, there is increased emphasis on
physical attractiveness in the selection of a sexual partner (Buss,
1994). When competing amongst each other for the attentions of a
low-investing partner, women emphasize their own sexuality and also
use sexual favors to manipulate men (Cashdan, 1993; Townsend, 1998).
Thus, if she wishes to leave an undesirable home environment, a young
woman may initiate a cohabiting relationship to obtain free
accommodation (Musick, 1993). Male partners are likely to be
physically strong and socially dominant (Palmer and Tilley, 1995).
From the perspective of a social worker, it is difficult to see
displays of aggressive masculinity, or promotion in a criminal
organization, as measures of social success but poor women are
attracted to socially dominant men for the same reason that
middle-class women are likely to be attracted to mild-mannered
professional men with high earning ability - these are different
measures of social success in very different social environments. By
being attracted to dominant men, women in poor neighborhoods acquire
at least temporary access to resources (Buss, 1999; Cashdan, 1993).
They also acquire the genetic basis of social success that contributes
a competitive advantage to their children. These adaptive
considerations are relevant to any comprehensive account of
reproductive choices underlying single teen parenthood but they are
unlikely to enter the lexicon of social workers.
One of the most interesting aspects of sexual behavior in an
economically depressed environment - one having an unusually difficult
marriage market for women - is that many young women view motherhood
in a very positive light and rarely as a mistake. Many look forward to
becoming pregnant as a way of obtaining someone to love. Birth of a
first baby may also constitute a rite of passage that provides entry
to the world of adults and the society of other young mothers (Musick,
1993). Their optimism in the face of formidable difficulties may be
one of the most remarkable examples of adaptive modulation of
psychological development to a niche of low paternal investment.
Willingness to assume the burden of rearing children alone may stem
from such optimism. Alternatively, it might reflect unsuitability of
biological fathers for the social role of being a parent. Although a
nurturant father may contribute a great deal to the happiness, health,
and social prospects, of offspring, this argument cuts both ways and
antisocial fathers can have the opposite effect. Indeed,
criminologists have recently found evidence that living with a
criminal father makes children more likely to commit serious crimes
(Jaffee, Moffitt, Caspi, and Taylor, 2003). Women living in
economically depressed neighborhoods might sometimes prefer to raise
their children alone if the presence of an antisocial father increased
the likelihood of their children getting involved in criminal
enterprises at considerable risk to their lives and liberty.
Interview research on poor single mothers in the U.S. finds that many
consider teenage childbearing both acceptable and normal (Musick,
1993). They deny the claims of social scientists that they are
damaging their own futures, or doing a disservice to their communities
by raising children who are at higher risk of criminality, drug
addiction, poverty, and so forth. Motherhood provides many of these
young women with a sense of optimism, purpose and meaning in their
lives and allows them to hope for a better future. One of Judith
Musick's (1993) informants articulated these sentiments clearly in a
"I Like it when people notice I'm having a baby. It gives me a good
feeling inside and makes me feel important." "Baby will be here any
day now and I will be a proud Teen Mom with my head held high." pp.
While single parenthood increases, almost inevitably, with declining
marriage prospects for women this is not the complete picture. The
modern environment evidently creates situations in which single
parenthood may actually be the desirable, or preferred option, even
though such a scenario was rare, or nonexistent, throughout the
two-million-year-plus history of our species. Before taking up that
theme in relation to changes in family structure in Sweden, it is
desirable to say something about "values" explanations of sexual
behavior that remain influential among scholars.
Values and the Single Mother
Values interpretations of human sexual behavior rest on the notion of
free will, i.e., that there are good and bad options that are
voluntarily chosen by freely-acting agents. The concept of free choice
of family structure, although widely accepted is problematic for
scientists: if each individual was really autonomous, social
scientists would be irrelevant in the sense that they could not
predict human behavior.
Even if belief in free will is largely inconsistent with scientific
inquiry, social scientists are forced to come to terms with arguments
that human behavior is determined by "values" that are either
propagated passively into individuals by their social environment, or
chosen voluntarily from an array of alternatives. They do so in at
least three distinct ways. The first is to interpret free will as a
popular illusion irrelevant to scientific analysis. The second is to
write free will off as a source of noise, or unexplained error in the
data. The third is to use it as an independent variable, or predictor.
This can be done in various ways, including experiments that either
encourage, or frustrate a person's sense of autonomy. In one
well-known experiment (Lepper and Greene, 1975) children who were paid
for drawing with felt-tipped pens lost their enthusiasm for this
activity when payments were stopped, thereby providing evidence that
they are governed by intrinsic motivation for some behavior that can
be affected by providing external rewards.
In social research, the third of these alternatives is frequently
employed when choices are studied in the form of attitudes measured at
an earlier point in time to see whether they are helpful in predicting
subsequent behavior. As intimated above, this enterprise has produced
mixed results. Evidence suggests that, sexual behavior affects sexual
attitudes just as much as sexual attitudes affect behavior (Moors,
2000). If attitudes and behavior are not clearly separable, they do
not satisfy the criterion of independence between causes and effects
that is a fundamental, assumption of scientific explanation. If
behavioral attitudes, or self-reported choices, are to avoid
tautology, (i.e., circularity), and provide useful scientific
explanations of behavior, they must be truly independent of the
behavior they are used to predict.
Even if sexual attitudes could be separated from behavior, there are
many reasons why individual behavior might not conform to attitudes,
or preferences, illustrating a further weakness in values as a
scientific construct. A person who is addicted to cigarettes may hate
their addiction, for example, but feel powerless to stop smoking. The
social environment often frustrates individual choices, as well, and
this is clearly true in the case of single parenthood that may be a
product of limited marital opportunities for young women. Thus,
research on the attitudes to marriage of young African American women
found that they strongly endorsed the value of marriage at a time when
few Black women could hope to marry before having their first child.
Moreover, exactly the same proportion of African American women as the
rest of the population believed that it was desirable to marry before
raising a family, although they were more than twice as likely to do
the opposite, i.e., raise their first child outside marriage (South,
The mismatch between family aspirations and actual reproductive
behavior is not peculiar to African Americans, of course. Thus, the
majority of Americans believe strongly in the permanence of marriage,
even though there has been a sharp rise in divorce rates, and in
numbers of cohabiting couples, who substitute an informal, often
temporary, union for a more permanent, more binding one (Smock, 1999).
Despite these inconsistencies, the married family remains the
statistical norm in the sense that nine Americans out of 10 still
marry and that the majority of children spend most of their childhood
in married households (including step parents, Wellner, 2002).
In many European countries, including France, where more women aged
20-24 yr now live with their boyfriends than live with husbands,
matters are very different (Ekert-Jaffee, and Solaz, 2001).
Approximately 85% of French marriages begin as cohabiting
arrangements. Sweden is an interesting country in the sense that
single parenthood is currently the norm there. This might be a
misleading conclusion, however, because unmarried Swedish women are
quite likely to be living with the father of their children.
Single Parenthood in Sweden
Sweden is sometimes seen as the exemplar of declining marriage and
consequently of increasing levels of single parenthood. Thus, Swedish
marriage rates declined 40% between 1966 and 1974 alone and are
currently at a historic low as well as being one of the world's lowest
(Popenoe, 1988). The decline in marriage rates is attributable to a
concurrent rise in cohabitation rates. If couples may live in the same
home and enjoy all the benefits of marriage without a permanent
commitment, why should they marry?
Widespread failure to marry is not the only sign of weakness in
Swedish marriages. Despite unusually low marriage rates, that would be
expected to screen out many potentially incompatible marriages,
Swedish marriages are highly unstable compared to other countries at a
similar level of economic development. At the end of the twentieth
century, Sweden's divorce rate, calculated as a proportion of all
marriages, stood at 64%, second only to that of Russia where 65% of
marriages ended in divorce (Moffett, 2002).
By 1990, about 50% of Swedish men aged 25-29 were cohabiting. As a
result, half of births were outside marriage (Chesnais, 1996).
Traditional marriages are little more than a historical curiosity and
there has been a rapid increase in the number of single young Swedes
living alone. Thus, in downtown Stockholm just 37% of households
contain married people. With 85% of young women with children under
seven in the workforce, the young home maker has receded into history
(Sweden's Splashy Women, 1996).
Although most births are to single mothers in a technical sense, as a
practical matter the great majority of young children live with both
parents. It might thus appear that the transition in Swedish families
is more a question of appearance than reality. Yet, this is not true
because cohabiting unions dissolve much more rapidly than marriages,
even in a country like Sweden that has an exceptionally high divorce
rate (Popenoe, 1988). In one study of U.S. women born between 1936 and
1960, for example, the dissolution rate for cohabiting couples with
one child was triple that of comparable married couples (Smock, 2000)
and a similar pattern is seen in Sweden (Popenoe, 1988).
Although the data on single parenthood in Sweden may thus exaggerate
the lack of commitment of fathers to their children, high ratios of
births to single women are nevertheless correlated with a relative
lack of commitment of parents to a permanent relationship that reduces
the amount of time that fathers will spend living in the same home as
their children. Why do so many Swedish couples, compared to the U.S.
and other developed countries, avoid marrying before reproducing? The
conventional answer to this question may be summed up in two words
"welfare state." The Swedish state is so generous in its support of
mothers and children that women raising children outside marriage are
not exposed to the economic risks encountered by single mothers in the
U.S., for example.
A comprehensive discussion of the historical roots of the Swedish
welfare state is outside the scope of this paper but a few points bear
emphasis. The Swedish welfare state grew out of perceived problems of
declining population but many of its current characteristics were
designed to solve the conflict between careers and family faced by
women in most developed countries (Carlson, 1990) so that more married
women could work, thereby boosting the Swedish economy. The Swedish
solution to this conflict was to nationalize many of the economic
functions of the traditional family so that it was easier for Swedish
women to raise children without economic cooperation from husbands.
Tax reforms of the 1970s also increased the financial incentive for
women to work, and reduced their economic dependence on husbands.
Thus, high tax rates for jointly-filing married couples were
eliminated and married people were taxed separately (Carlson, 1990).
Married women's earnings were no longer vulnerable to the high tax
rates that had seriously undermined the benefits of a second household
income to the extent of discouraging married women from going to work
Such changes in the tax code, as well as providing daycare
entitlements for mothers, were successful at increasing female labor
participation. By 1995, 85% of Swedish women worked outside the home,
the highest participation seen in any industrialized country and twice
the labor force participation of Italian women, for instance. Many
(40%) worked part-time, however, thus limiting potential conflicts
between career and family (Home Sweet Home, 1995).
Despite working part time, Swedish women do not lose occupational
prestige as a consequence. Gender equality is vigorously promoted and
women enjoy equal status with men in most occupations (Sweden's
Splashy Women, 1996). This is certainly true of politics. After the
1994 election, women held 41% of the seats in the Riksdag, the highest
proportion of female political representation in any country, and
considerably higher than the 14% of women in the U.S. House of
Representatives and in the Senate (as of 2003). Half of the cabinet
members (11 of 22) were also women. (Academic life evidently lags
other fields in regard to gender equality. Thus, Swedish females must
publish twice as much as Swedish males to earn a fellowship in
medicine, for example, Wenneras and Wold, 1997).
Direct government support of Swedish children is generous. Free school
meals, and clothing, and good childcare benefits, mean that no mother
is dependent on her husband, or lover, for economic necessities for
herself or her children. A man's decision to leave his children does
not send the family on a downward spiral into hardship, or poverty, as
it does in most other countries. Aggressive enforcement of child
support laws also mean that a father's presence in the home is not
necessary to ensure his financial contribution to children. As a
result of these radical family policies, very few Swedish children
live in poverty. In 1990, only 7% of children lived in households with
an income under 50% of the national average. In other words, 93% of
children lived in comparative affluence (Home Sweet Home, 1995).
Conservative scholars have criticized the Swedish welfare state for
weakening married families by taking over many of the economic
functions previously fulfilled by fathers (Popenoe, 1988). Expansion
of the welfare state has indeed been accompanied by a rapid, and
historically unprecedented, increase in births outside wedlock, from
11% in 1960 to 53% in 1995 (Home Sweet Home, 1995). Although 19 out of
20 babies begin life under the same roof as their fathers most will
not reach maturity without experiencing parental separation.
Although Sweden has a very high ratio of children born to single
mothers, this does not have the same implications for children as it
would in many other countries. In addition to being materially
provided for, most Swedish children also spend the formative early
years of life in two-parent families. It is not too surprising that
children of single parents in Sweden turn out very much as children of
married couples do in other countries given that domestic arrangements
are quite similar despite the lack of a formal marriage contract.
In particular, Sweden does not have the social problems associated
with single parenthood among poor women in many other developed
countries. Birth rates to teenage women are very low, for example at
1% annually compared to 6% in the U.S. (Population Reference Bureau,
1998). This is all the more remarkable given that women are sexually
active from a comparatively early age (Carlson, 1990; Popenoe, 1988;
Weinberg, Lottes, and Shaver, 1995). The main reason for avoiding
unplanned pregnancies may be the widespread use of contraceptives that
are easily available and promoted by many years of public education in
Other factors matter also. One important factor underlying low rates
of single teenage childbearing is the fact that Swedish women have
unusually good career prospects. They are thus motivated to delay
having a family until they are established in careers (see Goldin,
It is interesting that Sweden has low rates of serious crime despite
its high rates of single parenthood and the presence of a substantial
immigrant population. Other countries with high ratios of single
parenthood often have high crime rates because so many children are
born in high-risk groups, specifically to poor single mothers. In
Sweden many of the births to nominally single parents are to mature
affluent women, and few are to poor teenagers. Considering each of
these factors, it is perhaps unsurprising that Sweden has much lower
rates of serious crime than would be predicted by the ratio of births
to single women. Compared to violent crime rates in the U.S., for
example, Sweden has ten times fewer assaults, two-and-a-half times
fewer rapes, and about 25% fewer murders. based on INTERPOL (1990)
The fact that the Swedish family system does not produce high rates of
crime or other social problems, suggests that single parenthood may be
less important than poverty in determining the social problems
associated with high nonmarital birth ratios in other countries. This
is a risky assumption for at least two reasons however. The first is
that Swedish children generally do live with their fathers in the
early years of life when the brain is particularly responsive both to
stressors and environmental impoverishment. The second is that the
increased stress in children's lives attributable to father absence,
as measured in terms of stress hormones (Flinn, 1999), may be more
pronounced in poor homes for various reasons. Thus, poverty is a
complex stressor and any kind of social support, particularly that
from co-residing fathers, could mitigate its effects on behavioral
development. As well as experiencing less stress due to their social
environment and living arrangements, children of affluent single
mothers may benefit from have more extensive social support networks.
So far as the evolutionarily-relevant aspects of the early environment
are concerned, being raised by a single mother in Sweden is evidently
not very different from being raised by married parents in other
countries. Having come to the end of this summary of data on single
parenthood from an ESS perspective, it is time to ask what this
perspective contributes to the problem that is new or worthwhile.
ESS: Of What Value for Research on Single Parenthood
The data on single parenthood suggest that ESS provides the kind of
large framework into which many kinds of evidence can be assimilated.
Thus, the response of single parenthood ratios to similar influences
across time and from one society to another is consistent with ESS
(assumption 3) but not with most other perspectives in the social
sciences. Moreover, there is little convincing evidence in support of
top-down values interpretations of societal variation and very good
evidence that such differences are mediated directly through
environmental influences on individuals (assumption 2). The most
important of such influences include the marriage market, and the
economic prospects of single women as compared to the overall
well-being of children in two-parent families.
Perhaps the most interesting aspect of the application of ESS to
single parenthood is the fact that sexual psychology of young women
and men varies predictably both as a function of the immediate social
environment, and as a function of the developmental social environment
(assumption 4). The most important aspect of such variation is
arguably the potential for paternal investment in children, as well as
the extent to which women are economically independent of such
investment (a circumstance that prevails in Sweden due to the
provisions of the welfare state) and in many economically developed
countries due to expanded professional opportunities for women.
A diminished capacity for paternal investment is characteristic of
poverty in modern societies, helping to account for variation in
sexual behavior, and single parenthood ratios, as a function of
income. Moreover, research on brain development points to
psychological stress as a possible mediator in the ontogeny of
differing patterns of sexual behavior as a function of parental
income. Presumably, this example of evolved developmental plasticity
would have tracked very different stressors in the evolutionary past,
perhaps a scarcity of food rather than the modern stimulus of
insufficient monetary resources.
Scientific theories perform two essential functions. They organize
information and allow it to be stored in an orderly fashion, rather
like the ordered arrangement of merchandise in a warehouse. Large
scale theories, like ESS can be though of as providing a great deal of
space where new information can be deposited. In addition to the role
of organizing information, they stimulate research. This is analogous
to the owner of a warehouse finding that a bay of the warehouse is
empty and sending out to the supplier for the missing item. (In this
case, of course, the role of supplier is performed by researchers and
scientific knowledge is steadily accumulated instead of ebbing and
flowing as in a real warehouse).
This paper demonstrates that ESS can accommodate a great deal of
information in an orderly fashion. As far as the function of
stimulating research is concerned, it should be obvious that the data
reviewed here merely scratches the surface of potential research
projects in this field. Even so, ESS offers the prospect of revealing
new phenomena or helping us to see established facts in a new light.
Thus, the persistence of young single parenthood in economically
distressed circumstances that is often dismissed as a pathological
phenomenon should probably be seen as an adaptive response to a
developmental environment characterized by reduced paternal
investment. In any case, social workers who fail to make this
connection are (as they currently accept) singularly unlikely to
succeed in producing behavioral changes. The success of ESS in
reconciling many different types of data offers hope that it may do
the same for other content areas. One limitation on this conclusion is
that most of the data come from economically developed countries where
monogamy is the norm. If anthropologists were to apply this approach
to subsistence societies, where marriage systems are different, there
is no guarantee that they would draw similar conclusions. On the other
hand, the fact that this approach works for modern societies means
that it passes a more severe test given that our behavior has diverged
more from subsistence ancestors.
In summary, a few simple evolutionary concepts help to explain a great
deal of the variation in single parenthood across time, countries,
ethnic groups, and economic classes. This supports the view that the
concept of adaptation can be applied to modern societies, even those
that have passed through the demographic shift. Doing so not only
provides a heuristically useful means of drawing together a great deal
of information from many disciplines (including evolutionary biology,
anthropology, history, health, sociology, psychology, and economics
among others) but offers the prospect of a social science that
transcends disciplinary boundaries and may provide universal
explanations for social behavior that can be applied at any time,
place, or historical context, thus satisfying the basic scientific
criterion of universality of explanation and evading the pitfalls of
A reviewer of this paper complained that the assumptions of ESS are
not new and this is arguably true if they are taken piecemeal. The
focus of the new research strategy is not on any individual
assumption, however, but on what they can accomplish if applied
simultaneously, something that has not been previously attempted. In
particular, ESS aims to unite the time scales of evolutionary
psychology and the social sciences. The data on single parenthood
demonstrate that this new approach offers a credible method for
uniting evolutionary psychology and the social sciences, a problem
that has perplexed scholars in these fields for many years (Barkow,
Cosmides, and Tooby, 1992).
Received 9 March, 2004, Revision received 31 March, 2005, Accepted 29
Abrahamson, M. (1998). Out-of-wedlock births: The United States in
comparative perspective. Westport, CT: Praeger.
Abrahamson, M. (2000). Case studies of surges in nonmarital births.
Marriage and Family Review, 30, 127-151.
Anderson, E. (1990). Streetwise. Chicago: University of Chicago Press.
Argyle, M. (1994). The psychology of social class. London Routledge.
Barber, N. (1995). The evolutionary psychology of physical
attractiveness. Ethology and Sociobiology, 16, 395-424.
Barber, N. (1998a). The role of reproductive strategies in academic
attainment. Sex Roles, 38, 313-323.
Barber, N. (1998b). Sex differences in attitudes to kin, security of
adult attachment, and sociosexuality as a function of parental
divorce. Evolution and Human Behavior, 19, 1-8.
Barber, N. (2000a). Why parents matter: Parental investment and child
outcomes. Westport, CT: Bergin and Garvey.
Barber, N. (2000b). On the relationship between country sex ratios and
teen pregnancy rates: A replication. Cross-Cultural Research, 34,
Barber, N. (2001). On the relationship between marital opportunity and
teen pregnancy: The sex ratio question. Journal of Cross-Cultural
Psychology, 32, 259-267.
Barber, N. (2002a). The science of romance. Buffalo, NY: Prometheus.
Barber, N. (2002b). Parental investment prospects and teen birth rates
of Blacks and Whites in American metropolitan areas. Cross-cultural
Research, 36, 183-199.
Barber, N. (2002c). Marital opportunity, parental investment, and teen
birth rates of Blacks and Whites in American states. Journal of
Cross-Cultural Research, 35, 263-279.
Barber, N. (2003). Paternal investment prospects and cross-national
differences in single parenthood. Cross-Cultural Research, 37,
Barber, N. (2004a). Kindness in a cruel world: The evolution of
altruism: The evolution of altruism. Buffalo, NY: Prometheus.
Barber, N. (2004b). Reduced female marriage opportunity and history of
single parenthood (England, Scotland, U.S.) Journal of Cross-Cultural
Psychology, 35, 648-651.
Barber, N. (2005). Educational and ecological correlates of IQ: A
cross-national investigation, Intelligence, 33, 273-284.
Barkow, J. H., Cosmides, L. and Tooby, J. (1992). The adapted mind:
Evolutionary psychology and the generation of culture. New York:
Oxford University Press.
Belsky, J., Steinberg, L. and Draper, P. (1991). Childhood experience,
interpersonal development, and reproductive strategy: An evolutionary
theory of socialization. Child Development, 62, 647-670.
Boyer, D. and Pine, D. (1992). Sexual abuse as a factor in adolescent
pregnancy and child maltreatment. Family Planning Perspectives, 24,
Buss, D. M. (1994). The evolution of desire. New York: Basic.
Buss, D. M. (1999). Evolutionary psychology: The new science of the
mind. Boston, MA; Allyn and Bacon.
Carlson, A. (1990). The Swedish experiment in family politics. New
Brunswick, NJ: Transaction.
Cashdan, E. (1993). Attracting mates: Effects of paternal investment
on mate attraction strategies. Ethology and Sociobiology, 14, 1-24.
Chesnais, J. C. (1996). Fertility, family, and social policy in
contemporary Western Europe. Population and Development Review, 22,
Comings, D. E., Muhleman, D., Johnson, J. P. and MacMurray, J. P.
(2002). Parent-daughter transmission of the androgen receptor gene as
an explanation of the effect of father absence on age of menarche.
Child Development, 73, 1046-1051.
Corliss, R. (2002, January 28). Does divorce hurt kids? Time, 40.
Corona, S. G. and Tidwell, R. (1999). Differences between adolescent
mothers and nonmothers: An interview study. Adolescence, 34, 91-97.
Cosmides, L. and Tooby, J. (1987). From evolution to behavior:
Evolutionary psychology as the missing link. In J. Dupré, (Ed.), The
latest on the best: Essays on evolution and optimality (pp. 277-306).
Draper, P. and Harpending, H. (1982). Father absence and reproductive
strategy: An evolutionary synthesis. Journal of Anthropological
Research, 38, 255-273.
Durrant, R. and Ellis, B. J. (2003). Evolutionary psychology. In M.
Gallagher and R. Nelson (Eds.), Comprehensive Handbook of Psychology,
Vol. 3 Biological Psychology (pp. 1-33). New York: Wiley.
Ekert-Jaffee, O., and Solaz, A. (2001). Unemployment, marriage, and
cohabitation in France. The Journal of Socio-Economics, 30, 75-97.
Ellis, B. J. (2004). Timing of pubertal maturation in girls: An
integrated life history approach. Psychological Bulletin, 130,
Ellis, B. J., Bates, J. E., Dodge, K. A., Ferguson, D. M., Horwood, J.
L., Petit, G. S., et al. (2003). Does father absence place daughters
at special risk for early sexual activity and teenage pregnancy? Child
Development, 74, 801-821.
Ember, C. R., and Ember, M. (1994). War, socialization, and
interpersonal violence. Journal of Conflict Resolution, 38, 620-646.
Eysenck, H. J. (1976). Sex and personality. London: Open Books.
Fessler, D. M. T. (2004). Shame in two cultures: Implications for
evolutionary approaches. Journal of Cognition and Culture, 4, 207-262.
Flinn, M. V. (1999). Family environment, stress, and health during
childhood. In C. Panter-Brick and C. Worthman, Eds., Hormones, health
and behavior, pp. 105-138. Cambridge: Cambridge University Press.
Fossett, M. A. and Kiecolt, M. J. (1991). A methodological review of
the sex ratio: Alternatives for comparative research. Journal of
Marriage and the Family, 53, 941-957.
Geary, D. C. (1998). Male, female: The evolution of human sex
differences. Washington, DC: American Psychological Association.
Geary, D. C., and Flinn, M. V. (2001). Evolution of human parental
behavior and the human family. Parenting: Science and practice, 1,
Goldin, C. (1995). Career and family: College women look to the past.
National Bureau of Economic Research, Working Paper # 5188.
Grayson, D. K., and Delpech, F. (in press). Ungulates and the
Middle-to-Upper Paleolithic Transition at Grotte XVI (Dordogne,
France). Journal of Archaeological Science.
Guttentag, M. and Secord, P. F. (1983). Too many women: The sex ratio
question. Beverly Hills, CA: Sage.
Hart, B. and Risley, T. (1995). Meaningful differences in the everyday
experience of young American children. Baltimore, MD: Paul H. Brookes.
Hetherington, E. M. and Kelly, J. (2002). For Better of for worse:
Divorce reconsidered. New York: W. W. Norton.
Hewlett, B. S. (Ed.). (1992). Father-child relations: Cultural and
biosocial contexts. New York: Aldine de Gruyter.
Home sweet home (1995, September 9). The Economist, 25-27.
INTERPOL (1990). International crime statistics. Paris: Author.
Jaffee, S. R., Moffitt, T. E., Caspi, A. and Taylor, A. (2003). Life
with, or without, father: Benefits of living with two biological
parents depends on the father's antisocial behavior. Child
Development, 74, 109-126.
Kaplan, H., Lancaster, J. B., Tucker, W. T. and Anderson, K. G.
(2002). Evolutionary approach to below replacement fertility. American
Journal of Human Biology, 14, 233-256.
Landry, D. J. and Forrest, J. D. (1995). How old are U.S. fathers.
Family Planning Perspectives, 27, 159-161, 165.
Langford, C. M. (1991). Birth control practice in Great Britain: A
review of the evidence from cross-sectional surveys. Population
Studies, 45, S49-68.
Lepper, M. R. and Greene, D. (1975). Turning play into work. Journal
of Personality and Social Psychology, 31, 479-486.
Lopreato, J. and Crippen, T. A. (1999). Crisis in sociology: The need
for Darwin. Somerset, NJ; Transaction.
Lupien, S. J., King, S., Meaney, M. J. and McEwen, B. S. (2001). Can
poverty get under your skin? Basal cortisol levels and cognitive
function in children from low and high socioeconomic status.
Developmental Psychopathology, 13, 653-676.
Moffett, J. (2002). East: Effects of divorce on happiness. Radio Free
Europe/ Radio Liberty. Accessed at http:///www.rfert.org on 10/22/02.
Moors, G. (2000). Values and living arrangements: A recursive
relationship. In L. J. Waite, (Ed.), The ties that bind: Perspectives
on marriage and cohabitation (pp. 212-226.). New York: Aldine de
Musick, J. S. (1993). Young, poor and pregnant: The psychology of
teenage motherhood. New Haven, CT: Harvard University Press.
O'Connor, T. G., Caspi, A., DeFries, J. C. and Plomin, R. (2000). Are
associations between parental divorce and children's adjustment
genetically mediated: An adoption study. Developmental Psychology, 36,
Palmer, C. T. and Tilley, C. F. (1995). Sexual access to females as a
motivation for joining gangs: An evolutionary approach. The Journal of
Sex Research, 32, 213-217.
Pittman, K., and Govan, C. (1986). Model programs: Preventing
adolescent pregnancy and building youth self-sufficiency. Washington
DC: Children's Defense Fund.
Popenoe, D. (1988). Disturbing the nest: Family Change and decline in
modern societies. Hawthorne, NY: Aldine de Gruyter.
Popenoe, D. (1996). Life without father. New York: Martin Kessler/Free
Population Reference Bureau (1998). World population data sheet.
Washington, DC: Author.
Quinlan, R. J. (2003). Father absence, parental care, and female
reproductive development. Evolution and Human Behavior, 24, 376-390.
Shorter, E. (1975). Illegitimacy, sexual revolution, and social change
in modern Europe. In T. K. Rub and R. I. Rotberg, (Eds.), The family
in history: Interdisciplinary perspectives (pp. 48-85. New York:
Simpson, J. A., and Gangestad, S. W. (1992). Sociosexuality and
romantic partner choice. Journal of Personality, 60, 31-51.
Smith, P. B. (2004). Nations, cultures, and individuals: New
perspectives and old dilemmas. Journal of Cross-Cultural Psychology,
Smock, P. J. (2000). Cohabitation in the United States. Annual Review
of Sociology, Annual 2000, 1-20.
South, S. J. (1993). Racial and ethnic differences in the desire to
marry. Journal of Marriage and the Family, 55, 357-370.
South, S. J. (1996). Mate availability and the transition to unwed
motherhood: A paradox of population structure. Journal of Marriage and
the Family, 58, 265-279.
South, S. J., and Lloyd, K. M. (1992). Marriage opportunity and family
formation: Further implications of imbalanced sex ratios. Journal of
Marriage and the Family, 45, 440-451.
Staples, R. (1985). Changes in black family structure: The conflict
between family ideology and structural conditions. Journal of Marriage
and the Family, 51, 391-404.
Sweden's splashy women (1996, September 7). The Economist, 340, 52.
Symons, D. (1979). The evolution of human sexuality. New York: Oxford
Teicher, M. H., Andersen, S. L., Polcari, A., Anderson, C. M. and
Navalta, C. P. (2002). Developmental neurobiology of childhood stress
and trauma. Psychiatric Clinics of North America, 25, 397-426.
Townsend, J. (1998). What women want - what men want. New York: Oxford
Waite, L. J. and Gallagher, M. (2000). The case for marriage. New
Wallerstein, J. S. (1998). Children of divorce: A society in search of
policy. In M. A. Mason, A. Skolnick, and S. D. Sugarman, (Eds.), All
our families: New policies for a new century. New York: Oxford
Wallerstein, J. S., and Blakeslee, S. (1996). Second chances: Men,
women, and children a decade after divorce. New York: Mariner.
Weinberg, M. S., Lottes, I. L. and Shaver, F. M. (1995). Swedish or
American heterosexual college youth: Who is more permissive? Archives
of Sexual Behavior, 24, 409-437.
Wellner, A. S. (2002). The marriage habit: Baby Boomers may have
believed in free love, but now they're hooked on matrimony. Forecast,
Wenneras, C. and Wold, A. (1997). Nepotism and sexism in peer review.
Nature, 387, 341-343.
Whitehead, B. D., and Popenoe, D. (2002). The state of our unions: The
social health of marriage in America. Newark, NJ: The National
Marriage Project, Rutgers University.
Whitman, D. (1996, December 9). White-style urban woes: Why violence
and social problems are taking their toll in South Boston. U.S. News
and World Report, 46-49.
Wilson, W. J. (1997). When work disappears: The world of the new urban
poor. New York: Vintage.
Nigel Barber: mailto:nbarber at ime.net
More information about the paleopsych