A short video: http://online.wsj.com/article/SB1000...leTabs%3Dvideo

A short excerpt:
Our Kinder, Gentler Ancestors





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 égalité 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.

ETA: "Ardi" topped Time's list of the Top 10 Scientific discoveries of 2009.