Among bonobos (formerly known as pygmy chimps), older females often protect younger ones against male harassment:Bonobo
This behavior is especially remarkable because female bonobos, unlike some other species of apes, typically leave home at adolescence and join other groups, so adult females in a bonobo band mostly aren't relatives. Yet they form coalitions with unrelated females. Bonobo society has been described as more matriarchal than that of common chimpanzees; males derive their status from the status of their mothers. Bonobos have a reputation as the "make love, not war" apes because their social interactions depend more on sexual overtures than on aggressive dominance displays. They've even been known to make conciliatory sexual gestures toward members of other troops rather than attacking them.
Many behaviors formerly thought to set apart human beings as unique among primates have been observed in chimpanzees, e.g., tool-using, cooperative hunting for meat, and, sadly, rape, murder, and something like war. Bonobos especially demonstrate such features as non-reproductive sex for purposes of affection and bonding, oral sex, the importance of the clitoris in erotic stimulation, same-sex erotic activity, and face-to-face intercourse. The riddle of why human females ceased to have estrus cycles becomes less significant when we learn about non-reproductive intercourse among bonobos. The status of "receptive" to mating vs. "non-receptive" turns out to be a continuum rather than all or nothing.
These apes can shed light on human social evolution. They still, however, leave unresolved the big differences between Homo sapiens and all other primates—habitual bipedalism and the loss of most body hair. We're the only "naked apes." As Elaine Morgan discusses at length in her fascinating books on the "aquatic ape hypothesis," the replacement of fur with fat is unusual only among land animals. I still find her arguments compelling, even if she may have made some errors in detail and if a few of the big problems of human development she tackles in THE DESCENT OF WOMAN (e.g., intra-species aggression, perpetual sexual receptivity) have become less problematic in recent decades.
Jared Diamond, author of GUNS, GERMS, AND STEEL, also wrote THE THIRD CHIMPANZEE, which explores human evolution on the premise that an alien observer would view chimpanzees, bonobos, and Homo sapiens as three equivalent, closely related species. Diamond speculates on why our variety of "chimpanzee" evolved to become the dominant species on the planet.
Margaret L. CarterCarter's Crypt