Sex Unites Us

Our Species Has Spent Its History Mating with Anyone Close By     In graduate school for anthropology many decades ago, I learned that the phylogenic tree of human evolution was best represented by a sturdy central trunk. That trunk embodied the singular path of our species but there were also several weak branches sprouting off the truck that had withered and died. The roots of that central trunk were the first bipedal hominids, Australopithecines living about 4.5 million years ago, and the top canopy was Homo sapiens sapiens, modern humans. But…