The existence of DNA in all living things constitutes remarkable evidence of evolution. It strongly suggests a common origin of life, while cataloging the total set of DNA in a cell — its “genome” — also indicates the degree of relation among organisms. Yet many public disputes over evolution proceed as if the only proof on hand were a few dusty fossils.
Into this void of knowledge steps Nicholas Wade, a science reporter for The New York Times, whose timely and informative survey BEFORE THE DAWN: Recovering the Lost History of Our Ancestors (Penguin Press, $24.95) charts the recently compiled genetic evidence for the evolution and history of our species, revealing details, he says, “of the grand process that Darwin could see only in outline.” For starters, DNA helps show how our ancestors developed human form in the five million years since they began diverging from other apes. And as Wade ably explains, some genetic material is passed intact from mothers and fathers to children, while the rest generally mutates at a predictable rate. This allows scientists to trace the historical spread of humans, who left Africa in small numbers (some scientists say it could have been as few as 150 people) about 50,000 years ago, their descendants gradually scattering around the world.