[Paleopsych] BH: Support Found for Social Brain Theory
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Thu Aug 5 22:38:13 UTC 2004
Support Found for Social Brain Theory
Evidence links solving social problems to the evolution of the human brain
By Gabe Romain
4.8.5, 4:04 PM
The theory that solving social problems spurred the human brain to
surpass those of other species has received a boost.
Through tests on fossils and comparisons of our mental abilities to
those of other animals, researchers at the University of
Missouri-Columbia have found support for a theory proposed by
zoologist Richard Alexander: That humans evolved a large brain to
negotiate and manipulate complex social relationships.
"We term this scenario the 'ecological dominance--social competition'
model, and assess the feasibility of this model in light of recent
developments in paleoanthropology, cognitive psychology, and
neurobiology," say the researchers. "Alexander's model provides a
far-reaching and integrative explanation for the evolution of human
cognitive abilities that is consistent with evidence from a wide range
Big brain theories
Among the characteristics that differentiate humans from other species
are our cognitive abilities. The conditions favoring the evolution of
human cognitive adaptations, however, are mysterious.
Hypotheses have been proposed concerning the selective advantages of
cognitive change during human evolutionary history. Explanations
that point to ecological adaptations such as hunting and tool use have
been proposed. Such explanations, however, haven't been satisfactory
and none has achieved complete or general acceptance.
"Most traditional theories, including that of Charles Darwin,
suggested some combination of tool use and hunting were the key
selective pressures favoring big brains, but increasing evidence of
hunting and tool use in other species such as chimpanzees indicates
our ancestors were not unique in that regard," says study coauthor
Recent models based on social problem solving linked with ecological
conditions, say Flinn and colleagues in their study, offer scenarios
that are more convincing.
Social arms race
The hominid brain increased 250% in less than three million years,
particularly in brain areas involved in cognitive development. The
researchers credit the increasing importance of complex social
coalitions with the human brain's evolution.
As ecological dominance increased, adaptations that facilitated
kinship- and reciprocity-based social partnerships arose. These
adaptations include social, cognitive and linguistic capacities
because such skills would have allowed people to better anticipate and
influence social interactions with other increasingly sophisticated
Evidence gathered supports the idea that an "autocatalytic social arms
race" was initiated that eventually resulted in traits characteristic
of the human species, such as concealed ovulation, extensive
biparental care, complex sociality, and an extraordinary collection of
cognitive abilities, say the researchers.
"We think this model explains the data better than any other model,"
says study coauthor Carol Ward. "The tests available, although not
comprehensive, certainly support it and provide a better explanation
than the other ideas out there."
The research will be published in a special issue of Evolution and
Human Behavior honoring Alexander.
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