|
The human brain is astonishingly different from the brain of
any other animal. Why? Have we somehow fooled Mother Nature and escaped from the
laws of evolution? Written like a detective story, this
book brings together a wealth of new research from paleontology, genetics, and
neurobiology to explain the runaway evolution of the human brain. Evolutionists
and human paleontologists have tended to assume that our intellect began to burgeon
when our ancestors developed the ability to walk upright, to grasp and carry objects,
or to form cooperative groups for hunting. While these and many other factors
are important, this book shows that they are only some of the latest steps in
a long evolutionary story that began a billion years ago. By now, the brains of
many different animals are much larger than those of their predecessors and are
superbly adapted to environments that have slowly become more complex. But our
own distant ancestors were the only ones to enter a new evolutionary path, a feedback
loop that involved their brains, their bodies, and an ever more complicated environment
that they largely created themselves. The result, for better and sometimes for
worse, is our own astonishing species. The author
shows how this view of our evolution as a runaway process casts light on a number
of major questions that recent discoveries have raised about our past. These include
the identity and true role of the mitochondrial Eve, the origin of human diversity,
and the confusion and controversy surrounding our fossil record. Two major views
of recent human evolution hinge on the time at which people like ourselves first
arose. Did they do so in several different parts of the Old World, the so-called
"multiple origins" model, or did they appear suddenly and recently,
perhaps driving all the primitive hominids to extinction? The first model is favored
by many anthropologists; the second, by many geneticists. While it is not yet
possible to decide with certainty between the two, the book details how the driving
force of runaway brain evolution is so great that it can easily account for multiple
origins. Turning to the evolution of the brain itself,
the author recounts the escape of our ancestors from the "stupidworlds"
of the past. He shows how, as a result of this escape, our brains have evolved
into sponges for knowledge. They are so versatile, and have been driven by such
strong evolutionary pressures, that fundamental human capabilities such as language
can be traced to many different parts of the brain that have simultaneously increased
in complexity. Using a vivid series of examples, the book details scientists'
growing knowledge of the kinds of genetic changes that have powered the runaway
process.
Written by a scientist whose previous books have explored the whole
sweep of evolution and the complexities of the human genome, The Runaway Brain
casts a brilliant light on human intellect and human nature. Christopher
Wills is professor of biology at the University of California, San Diego, and
the author of The Wisdom of the Genes: New Pathways in Evolution and Exons,
Introns, and Talking Genes: The Science Behind the Human Genome Project, both
published by Basic Books. |
