The scholarly war between the genetic and social bases for humanity’s penchant for war continues.

Chimpanzees are highly intelligent animals, capable of great acts of empathy, technological sophistication, culture and cooperation. But they can also be murderers. Groups of chimps, mostly male, will mount lengthy aggressive campaigns against individuals from other groups, attacking them en masse and beating them to death. Their reasons for such killings have long been a source of debate among zoologists, but the aftermath of the Ngogo murders reveals an important clue. After the chimps picked off their neighbours, they eventually took over their territory. It seems that chimps kill for land.

John Mitani’s research seems to buttress the genetic view that warfare is a behavior that humans share with apes, possibly originating with the common ancestor of both. But, the social basis view is not vanquished.

But Mitani’s observations do rule out at least one idea behind chimp aggression – that it’s a side effect of humans. Some zoologists had suggested that by providing food to wild chimps, we were instigating conflict between them, but that’s clearly not the case in Ngogo.

Much of this behaviour might seem familiar, for it has poignant echoes of human warfare. After all, we also kill each other over resource. Richard Wrangham, a primatologist from Harvard University, has suggested that understanding the reasons behind chimp violence could help us to understand and address “the roots of violence in our own species”. Even so, Mitani is very careful about drawing an analogy between chimp and human aggression, given the myriad of reasons that humans have for waging war.

Chimp expert Frans de Waal appreciates his caution. He says, “There have been claims made in the past that since chimps wage war and we do as well it must be a characteristic that goes back 6 million years, and that we have always waged war, and always will.

“There are many problems with this idea, not the least of which is that firm archaeological evidence for human warfare goes back only about 10-15 thousand years. And apart from chimpanzees, we have an equally close relative, the bonobo, that is remarkably peaceful. The recent discovery of Ardipithecus also adds to the picture, as the suggestion has been that Ardi was relatively peaceful too. The present study provides us with a very critical piece of information of what chimpanzees may gain from attacking neighbours. How this connects with human warfare is a different story.”

A related discovery, of another hominid fossil, Big Man, in Ethiopia’s Afar region, strengthens the the view, that apes and humans have evolved in different physiological directions, leading to differing social development.

Haile-Selassie’s team has dubbed its new find Kadanuumuu, which means “big man” in the Afar language. At an estimated 5 to 5½ feet tall, he would have towered over 3½-foot-tall Lucy. Excavations between 2005 and 2008 in a part of Afar called Woranso-Mille — about 48 kilometers north of where Lucy’s 3.2-million-year-old remains were found — yielded fossils from 32 bones of the same individual.

Big Man’s long legs, relatively narrow chest and inwardly curving back denote a nearly humanlike gait and ground-based lifestyle, according to a preliminary report published online June 21 in the Proceedings of the National Academy of Sciences. Lucy has often been portrayed as having had a fairly primitive two-legged gait and a penchant for tree climbing.

Big Man’s humanlike shoulder blade differs as much from those of chimpanzees as it does from those of gorillas, Haile-Selassie says. The shape of that bone, combined with characteristics of five recovered ribs, suggest to Haile-Selassie’s team that Big Man’s chest had a humanlike shape. Earlier reconstructions of Lucy’s rib cage had endowed her with a chimplike, funnel-shaped chest.

So despite chimps’ close genetic relationship to people, he says, this new fossil evidence supports the view that chimps have evolved a great deal since diverging from a common human-chimp ancestor roughly 7 million years ago and are not good models for ancient hominids.

Big Man’s shoulder blade bolsters recent analyses of 4.4-million-year-old Ardipithecus ramidus that also challenge traditional views of ancient hominids as chimplike.

The hope, that humanity can evolve from its uses for war, continues, too.

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Filed under: Academia, Science Tagged: ardipithecus ramidus, big man, chimpanzees, john mitani, lucy, war