[Paleopsych] NYTBR: (Dawkins) 'The Ancestor's Tale': You Are Here
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Tue Oct 19 16:51:27 UTC 2004
'The Ancestor's Tale': You Are Here
New York Times Book Review, 4.10.17
By CARL ZIMMER
THE ANCESTOR'S TALE
A Pilgrimage to the Dawn of Evolution.
By Richard Dawkins.
Illustrated. 673 pp. Houghton Mifflin Company. $28.
I once attended a conference about systematics -- the
classification of species -- and felt as if I were looking
at Mount Rushmore with a magnifying glass. The names alone
-- Tetraconata, Amoebozoa, Ecdysozoa, Oomycota,
Neomeniomorpha -- were overwhelming. Speaker after speaker
hypothesized about how various species were related --
whether springtails or bristletails were the closest
relatives of winged insects, whether sponges all descended
from a common ancestor, whether slime molds are really
molds. I stumbled out of the lecture hall desperate for the
big picture. And suddenly I saw it, on a five-foot-square
poster taped to a wall.
It showed an evolutionary tree by David Hillis of the
University of Texas and his colleagues. The tree displayed
the relationships of 3,000 species of animals, plants,
fungi and microbes. The scientists drew it as a kind of a
surreal bicycle wheel, each species represented as a tip of
a branch along its rim. As my eye moved toward the center
of the tree, I moved back through time, our own branch
joining together with that of chimpanzees, our closest
living relatives. Farther in, all living mammals merged
into a common ancestor, and then all vertebrates, and then
all animals. The deepest branches of the tree met at the
very center, which represented the common ancestor of all
living things. Hillis's tree included only a sampling of
life's diversity, which has been estimated at 10 million to
100 million species. Yet its tiny branch tips were so
densely packed that it was hard to find our own.
Fortunately, the poster included a big arrow pointing to
Homo sapiens, reading: ''You are here.''
The tree of life was Darwin's greatest and most dislocating
discovery. Our species is not the center of nature; it is
one among millions of branches, its ancestry mingled with
that of pufferfish and puffballs. Yet outside of
systematics circles, few people understand how scientists
assemble the tree of life, or use it to learn how life has
evolved. In ''The Ancestor's Tale,'' the Oxford University
zoologist Richard Dawkins offers a tour through the tree's
thickety depths. Dawkins, the author of the scientific
classics ''The Selfish Gene'' and ''The Blind Watchmaker,''
is an excellent guide, both a profoundly original
scientific thinker and a marvelously adept explainer.
He organizes ''The Ancestor's Tale'' as a pilgrimage,
leading readers from the tip of our own branch down to the
base of the tree of life. He moves back through time,
stopping occasionally so we humans can be joined by related
species -- first by chimpanzees, which share a common
ancestor with us six million to seven million years ago,
then by gorillas, orangutans, gibbons, Old World monkeys
and so on. Dawkins patterns his book on ''The Canterbury
Tales'' of Chaucer, breaking it up into ''The Marsupial
Mole's Tale,'' ''The Elephant Bird's Tale'' and many
others. In each tale he looks at an aspect of the tree of
life or at evolution in general.
Together, the tales add up to an encyclopedia that sheds
light on some of the stranger features of the tree of life.
For example, it is tempting to look at the platypus, a
duck-billed mammal that lays eggs, as a living fossil
trapped in the past. In fact, the platypus is no more
primitive than we are. True, its ancestors branched off
from our own some 180 million years ago, before our more
recent ancestors evolved placentas and live births. But the
ancestors of today's platypuses were not frozen in time.
They evolved sophisticated adaptations of their own, like
sense organs in their bills that can detect faint electric
fields produced by other animals. From this perspective, it
is humans who are the living fossils. Dawkins not only
makes an important point here, but does it with flair. He
eloquently describes how platypuses combine information
from electric-sense organs with signals from mechanical
sensors in their bills, likening the process to our
measuring how far away a lightning bolt strikes by
comparing the flash to the thunder. ''When you think of a
platypus, forget duck,'' he writes. ''Think huge hand
feeling its way, by remote pins and needles; think
lightning flash and thunder rumbling, through the watery
mud of Australia.''
As enlightening as ''The Ancestor's Tale'' is, it could
have been better. Dawkins clearly wanted it to be more
literary, evocative and personal than his previous books.
But his efforts are often awkward and halfhearted, as when
he writes about earthworms. ''I am privileged to have seen
giant earthworms (Megascolides australis), in Australia,
said to be capable of growing to four meters long,'' he
announces. Cool, the reader thinks -- let's hear what that
was like. But Dawkins abruptly abandons earthworms
The structure of ''The Ancestor's Tale'' could have been
better as well. The backward pilgrimage is a brilliant
inspiration, which allows Dawkins to ease us into our
kinship with the rest of life. Neanderthals come early in
the book because of all other species they were our closest
relatives. It's not too much of a stretch to see a bond in
Neanderthals because they look so much like us. A
jellyfish, on the other hand, doesn't exactly seem like
family. In part, that's because the common ancestor of
jellyfish and humans lived perhaps a billion years ago. But
Dawkins introduces us to jellyfish only deep in the book,
after we've met many closer relatives.
At the same time, though, the book is wildly lopsided.
Dawkins spends nearly 500 pages on animals, and 100 on all
other life forms. Fungi, estimated to total 1.5 million
species, get four pages. The vast bulk of life, whether
measured by sheer biomass or by genetic diversity, lies
outside the animal kingdom. And not all the lessons about
evolution that the animal kingdom offers apply outside its
borders. While animals generally evolve into new species
when populations become isolated, plants can also form a
new species when two existing species interbreed. Fungi are
even weirder. They can form vast subterranean networks of
threadlike growths, which sometimes fuse with other
networks, mingling their DNA so that they wind up as
strange genetic chimeras, defying our notion of what it
means to be a genetically distinct individual. Bacteria and
other microbes are even more casual with their genes,
trading them like baseball cards.
Evolution not only has a different flavor outside the
animal kingdom; it also may give the tree of life a
different shape. Some scientists today argue that early
life did not follow the regular branching pattern of
evolution seen in animals. Instead of a tree, a better
metaphor might be a ring or a web. These are some of the
most important, most fascinating lines of research in
evolutionary biology, but Dawkins skims over them.
Despite these shortcomings, this is an ambitious, important
book rich with fascinating insights. Also, it couldn't come
at a better time. Evolutionary trees have become the lingua
franca of biology. Virus hunters draw them to find the
origin of SARS and H.I.V. Conservation biologists draw them
to decide which endangered species are in most urgent need
of saving. Geneticists draw them to pinpoint the genes that
have made us uniquely humans. Genome sequencers draw them
to discover new genes that may lead to new technologies and
medical treatments. If you want to understand these trees
-- and through them, the nature of life -- ''The Ancestor's
Tale'' is an excellent place to start.
Carl Zimmer's books include ''Soul Made Flesh'' and
''Evolution: The Triumph of an Idea.'' He also writes ''The
Loom,'' a blog about evolution.
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