July 2006

Kevin Arthur

nonfiction

Before the Dawn: Recovering the Lost History of Our Ancestors by Nicholas Wade

In Before The Dawn, Nicholas Wade tells the story of human evolution and migration that began five million years ago, when the first humans split from the apes, and continues today, with evidence showing that humans are still evolving. A second thread in the book tells how the new science of genetics is changing what we know about our history and the way we study it. Genetics is reaching outside biology into fields like linguistics and the social sciences, and is making controversial new assertions about racial and cultural differences.

Popular presentations of evolution often make it appear to be a linear progression: apes to Neanderthals to humans to cyborgs or whatever the futurists tell us. Wade shows how this is wrong, as Darwin knew. The proper picture is of a very dense tree, with us perched on only one branch among millions of close neighbors. The human line of evolution has had many branches and may generate more in the future. Just 50,000 years ago the physically modern Homo sapiens shared the planet with three other types of humans -- Neanderthals, Homo erectus, and the recently discovered Homo floresiensis. We don't yet know whether these others simply died out or were exterminated by our ancestors.

Genetics is allowing scientists to trace the heredity of a person living today back to the original groups of humans that migrated out of Africa 50,000 years ago. Your DNA fingerprint no longer identifies just you -- it now points to all your ancestors too. Scientists can trace paternal and maternal ancestry through your Y chromosome and mitochondrial DNA respectively. You can have this done for free by sending in a cheek swab to National Geographic's new "Genographic" project. In return they'll tell you which ancestral lines you belong to and place a dot on their map. The numerous privacy disclaimers and FAQs on their website indicate just how uneasy we might be if this information fell into the wrong hands. It's a short distance from lineages to concepts like pedigree and racial purity.

Wade writes that scientists are now able to measure genetic differences between virtually any groups that have lived apart. When distinct behaviors or characteristics emerge they inevitably get written into our genes and passed on. This means that geneticists can detect statistical differences between races and cultures, the implication being that this puts to rest any debate about race being a social construct. Wade similarly implies that critics of sociobiology and genetic determinism will at last be silenced (though the opposite seems to be true, as a recent highly critical review of the book in Nature shows).

Wade warns us rather dramatically that "however discomforting such findings may be, to falter in scientific inquiry would be to retreat into darkness." But this is admitting a rather strong faith in a very new science. Many of these findings date from 2003 or later, and the newness shows. Often Wade's descriptions feel qualified and tentative. A recent New York Times article by Wade told of a Miami professor of British descent who had his DNA analyzed using these methods. The results showed that he was descended from Genghis Khan of all people. Surprised, he got a retest, and learned that the first result was wrong.

Even when the bugs are worked out, it's unlikely that genetics will ever have the kind of explanatory power that many are assuming it will. Biologists are well aware that genes are only part of the story. Genetics is an important science, but we shouldn't take it as the last word.

Before the Dawn: Recovering the Lost History of Our Ancestors by Nicholas Wade
Penguin Press
ISBN: 1594200793
320 Pages