National Geographic : 2013 Mar
bonobos 107 nests at night, presumably for mutual security. Their diet, which is similar to the usual chim- panzee diet in most respects—fruit, leaves, a bit of animal protein when they can get it—differs in one signal way: Bonobos eat a lot of the herby vegetation that is abundant in all seasons—big reedy stuff like cornstalks and starchy tubers like arrowroot—which offers nutritious shoots and young leaves and pith inside the stems, rich in protein and sugars. Bonobos, then, have an almost inexhaustible supply of reliable munch- ies. So they don’t experience lean times, hunger, and competition for food as acutely as chim- panzees do. That fact may have had important evolutionar y implications. Bonobos do share one distinction with chim- panzees: Together they are the two closest liv- ing relatives of Homo sapiens. Back about seven million years ago, somewhere in the forests of equatorial Africa, lived a kind of proto-ape that was both their direct ancestor and ours. Then our lineage diverged from theirs, and by about 900,000 years ago, those two apes had diverged from each other. No one knows whether their last shared ancestor resembled a chimp, in anatomy and behavior, or a bonobo—but solving that uncertainty might say something about human origins too. Do we come from a long line of peace-loving, sex-happy, and female-dominant apes, or from a natural heritage of warfare, in- fanticide, and male dominance? Also: What happened in evolutionary history to make Pan paniscus the unique creature it is? Richard Wrangham has a hypothesis. Wrang- ham is a distinguished biological anthropologist and a professor in the Department of Human Evolutionary Biology at Harvard with more than four decades of experience studying primates in the wild. His work on chimpanzees dates back to his Ph.D. research at Tanzania’s Gombe Na- tional Park in the early 1970s and continues at Kibale National Park in Uganda. He addressed the subject of bonobo origins in a 1993 journal paper and then in a popular 1996 book, Demon- ic Males, co-authored with Dale Peterson. The The vast Congo River, comprising many large and small channels, has been an impassable barrier between bonobos and their ape kin. Chimps and gorillas live only on the right bank, bonobos only on the left. are behavioral, and the most conspicuous do involve sex.