OCTOBER 3, 2009


Our Kinder, Gentler Ancestors


Ardi casts doubt on the notion that we have an innate killer instinct



Are humans hard-wired to be ruthlessly competitive or supportive of one another?

The behavior of our ape relatives, known as peaceful vegetarians, once bolstered the view that our actions could not be traced to an impulse to dominate. But in the late 1970s, when chimpanzees were discovered to hunt monkeys and kill each other, they became the poster boys for our violent origins and aggressive instinct.


'Ardi' Fossil Altering Ideas on Human Evolution


The skeleton of Ardipithecus ramidus, an ancient fossil dubbed "Ardi," is radically changing our ideas about mankind's origins. Kent State University's C. Owen Lovejoy says Ardi shows our ancestors were more like us and less like chimps. WSJ's Robert Lee Hotz reports.

I use the term "boys" on purpose because the theory was all about males without much attention to the females of the species, who just tagged along evolutionarily. It was hard to escape the notion that we are essentially "killer apes" destined to wage war forever.

Doubts about this macho origin myth have been on the rise, however, culminating in the announcement this past week of the discovery of a fossil of a 4.4 million year old ancestor that may have been gentler than previously thought. Considered close to the last common ancestor of apes and humans, this ancestral type, named Ardipithecus ramidus (or "Ardi"), had a less protruding mouth equipped with considerably smaller, blunter canine teeth than the chimpanzee's impressive fangs. This ape's canines serve as deadly knives, capable of slashing open an enemy's face and skin, causing either a quick death through blood loss or a slow one through festering infections. Wild chimps have been observed to use this weaponry to lethal effect in territorial combat. But the aggressiveness of chimpanzees obviously loses some of its significance if our ancestors were built quite differently. What if chimps are outliers in an otherwise relatively peaceful lineage?

Consider our other close relatives: gorillas and bonobos. Gorillas are known as gentle giants with a close-knit family life: they rarely kill. Even more striking is the bonobo, which is just as genetically close to us as the chimp. No bonobo has ever been observed to eliminate its own kind, neither in the wild nor in captivity. This slightly built, elegant ape seems to enjoy love and peace to a degree that would put any Woodstock veteran to shame. Bonobos have sometimes been presented as a delightful yet irrelevant side branch of our family tree, but what if they are more representative of our primate background than the blustering chimpanzee?

The assumption that we are born killers has been challenged from an entirely different angle by paleontologists asserting that the evidence for warfare does not go back much further than the agricultural revolution, about 15,000 years ago. No evidence for large-scale conflict, such as mass graves with embedded weapons, have been found from before this time. Even the walls of Jericho—considered one of the first signs of warfare and famous for having come tumbling down in the Old Testament—may have served mainly as protection against mudflows. There are even suggestions that before this time, about 70,000 years ago, our lineage was at the edge of extinction, living in scattered small bands with a global population of just a couple of thousand. These are hardly the sort of conditions that promote continuous warfare.

The once-popular killer ape theory is crumbling under its own lack of evidence, with "Ardi" putting the last nail in its coffin. On the other side of the equation, the one concerning our prosocial tendencies, the move has been towards increasing evidence for humans as cooperative and empathic. Some of this evidence comes from the new field of behavioral economics with studies showing that people do not always adhere to the profit principle. We care about fairness and justice and sometimes let these concerns override the desire to make as much money as possible. All over the world, people have played the "ultimatum game," in which one party is asked to react to the division of benefits proposed by another. Even people who have never heard of the French enlightenment and its call for ˇgalitˇ refuse to play along if the split seems unfair. They may accept a split of 60 for the proposer and 40 for themselves, but not a 80 to 20 split. They thus forgo income that they could have taken, which is something no rational being should ever do. A small income trumps no income at all.

Similarly, if one gives two monkeys hugely different rewards for the same task, the one who gets the short end of the stick refuses to cooperate. We hold out a piece of cucumber, which normally entices any monkey to perform, but with its neighbor munching on grapes cucumber is simply not good enough anymore. They protest the situation, sometimes even flinging those measly cucumber slices away, showing that even monkeys compare what they get with what others are getting.

And then there is the evidence for helping behavior, such as the consolation of distressed group members, which primates do by means of embracing and kissing. Elephants give reassuring rumbles to distressed youngsters, dolphins lift sick individuals to the surface where they can breathe, and almost every dog owner has stories of concerned reactions by their pets. In Roseville, Calif., a black Labrador jumped in front of his friend, a six-year-old boy, who was being threatened by a rattle snake. The dog took so much venom that he required blood transfusions to be saved.

The empathy literature on animals is growing fast, and is no longer restricted to such anecdotes. There are now systematic studies, and even experiments that show that we are not the only caring species. At the same time, we are getting used to findings of remarkable human empathy, such as those by neuroscientists that reward centers in the brain light up when we give to charity (hence the saying that "doing good feels good") or that seeing another in pain activates the same brain areas as when we are in pain ourselves. Obviously, we are hard-wired to be in tune with the emotions of others, a capacity that evolution should never have favored if exploitation of others were all that mattered.


Frans de Waal, a professor of primate behavior in the psychology department at Emory University, is the author of "The Age of Empathy."