WHO WE ARE AND HOW WE GOT HERE

A surprising new description of how Homo sapiens originated in Africa and spread around the world.

In his first book, Reich (Genetics/Harvard Medical School) describes the revolution in his specialty, genomics, the branch of molecular biology that analyzes our genes, units of DNA that transmit hereditary information from parent to offspring. Since 2001, when scientists sequenced the human genome for the first time, technology has massively reduced the cost of the procedure. At the same time, researchers have become incredibly adept at extracting DNA from bones as old as 400,000 years. Readers who pay close attention will understand Reich’s explanation of what this reveals. As generations pass, strings of DNA in the genome split and recombine, and errors (mutations) appear in individual genes. Comparing one genome to another reveals the relationship between populations more accurately than comparing bones. Mutations appear at a regular rate, allowing researchers to measure time elapsed as evolution proceeds. “Since 2009,” writes the author, “…whole-genome data have begun to challenge long-held views in archaeology, history, anthropology, and even linguistics—and to resolve controversies in those fields. The ancient DNA revolution is rapidly disrupting our assumptions about the past.” Most agree that migrants from Turkey brought agriculture to Europe about 8,000 years ago. They once agreed that these migrants brought Indo-European languages spoken throughout most Western nations, but the studies in genomics reveal that the languages arrived with later migrants: a “ghost population” from the Russian steppes who also moved east and contributed genes to American Indians. Throughout the book, Reich includes numerous timelines, graphs, maps, and diagrams to assist readers in visualizing his material, but those who are not scientifically inclined may find the narrative difficult to follow—though ultimately rewarding.

Not an easy read, but an eye-opening account of significant scientific advances that throw a spectacular, often unexpected light on human prehistory.