New Books In World Affairs

First, the conventional wisdom. Because Homo sapiens are a young species and haven’t had time to genetically differentiate, we modern humans are all basically genetically identical. Because Homo sapiens figured out ways to use culture to overcome natural selection, human genetic evolution ceased ages ago. Because Homo sapiens are genetically very similar and not subject to natural selection, the differences that we see today among modern human groups are the result of cultural processes, not genes. Not so say Gregory Cochran and Henry Harpending in their challenging and sure-to-be-controversial new book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution (Basic Books, 2009). We are extraordinarily similar genetically, but the minor differences occasionally had very important consequences: a difference of one or two nucleotides–among billions–could mean life or death for entire populations.These minor differences, where advantageous, were selected for and spread in the ordinary natural sel