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Mark Pagel's new book, Wired for Culture: Origins of the Human Social Mind, leads readers to a startling view of human evolution.
It begins by recognizing this obvious yet profound aspect of Darwin's theory of natural selection: Modern humans are neither the goal nor the endpoint of the evolutionary process. We are merely one stage along a continuum that has been directed not by a plan but rather by external influences encountered by happenstance.
Climate, environment, diseases, and parasites have shaped our bodies and brains by favoring certain genetic traits over others. Each of us carries in our DNA an ancestral historical and geographical record.
We can read that record and find evidence of genetic innovations that spurred us toward language and a trait that is absent or very limited in other animals: brains that are wired for social learning, altruism, and the development of cultures.
Pagel sees those innovations as revolutionary. Once culture emerged, human evolution was no longer driven by the reproduction of genes and DNA alone. "Cultural survival vehicles," behavioral traits that could pass from one mind to another, evolved through a similar process of natural selection.
Not restricted by random mutations and sexual transmission, but rather driven by mental innovation and social interaction, cultural evolution can be far more rapid and dynamic than biological evolution.
In fact, Pagel argues that culture has become a more important influence on genetic evolution than environmental factors. Thus our physical evolution, including brain changes, is now more rapid than ever--and may be proceeding in an unexpected direction.
"Having steadily enlarged for roughly 2 million years, they have shrunk by around 10 percent in the last 30,000," he writes of our brains. "We also become less robust... during this time, so it might just be that our brains were adjusting to a reduced stature. But one of the most reliable differences between domesticated animals and their wild ancestors is that the domesticated ones have smaller brains: as a rule, domesticated animals are just a bit dim, or less 'street smart.' Could our brains have domesticated us as well."
That is not the only topic that readers are likely to find controversial. Pagel is clearly an atheist, yet he sees religion as an important and probably beneficial survival trait. Believers and nonbelievers alike will find something to take issue with. Readers who like being challenged will enjoy those controversial sections and will gladly spend several hours engaging in an intellectual wrestling match with the author.
Other readers should be warned: the book is often academic in tone and level of detail. For them, it may feel like a slog yet always interesting enough to keep turning the pages as they ponder what it means to be a member of a rapidly evolving, Wired-for-Culture species.