then relentlessly hunt them down. When they catch the victim, the attack is brutal, focused on body parts that are necessary for moving, communicating and reproducing. The attackers commonly have a numerical advantage over the victims, a ratio of at least three to one. This power imbalance reduces the costs of the attack by making it almost impossible for the victim to retaliate. Proof of this cost-benefit analysis comes from the fact that the attacking party rarely incurs injuries, whereas the victims rarely escape alive. The benefit of these attacks is that the attacking community gains access to additional resources by weakening the competitive strength of their neighbors. In a well documented case from Jane Goodall’s site in Gombe, Tanzania, one chimpanzee community literally eliminated their competitors in the neighboring community, absorbing the remaining individuals and land. Though such attacks are certainly not a daily affair, they occur with sufficient frequency and benefits to create a selective advantage for the winners.
The suite of behaviors that accompany coalitionary killing in chimpanzees has led several scientists, most notably Wrangham, to argue that this form of lethal aggression in chimpanzees is an adaptation, with deep parallels to human warfare. On this view, we inherited the upgrade to version 1.5 lethal aggression.
The claim that our capacity for killing, especially in war, is an evolved adaptation, is anathema to many, scholars in the humanities and social sciences. The visceral antagonism is triggered by the belief that biological explanations imply inevitability, and provide an excuse for the atrocities we create. For these scholars, war, and more generally, the high levels of killing observed among human populations, are recent, cultural concoctions, born out of human intelligence, the invention of projectile weapons, and high population density, to name a few. From this perspective, biology plays no meaningful role in our understanding of human violence. From this perspective, killing in chimpanzees looks nothing like killing in humans. This attitude echoes the famous 1986 Seville Statement on violence in which a group of distinguished scientists, including the ethologist Robert Hinde, the geneticist John Paul Scott, and the biological anthropologist Richard Leakey, sidelined biology with the following five statements:
1. "It is scientifically incorrect to say that we have inherited a tendency to make war from our animal ancestors."
2. "It is scientifically incorrect to say that war or any other violent behaviour is genetically programmed into our human nature."
3. "It is scientifically incorrect to say that in the course of human evolution there has been a selection for aggressive behaviour more than for other kinds of behaviour."
4. "It is scientifically incorrect to say that humans have a ‘violent brain'."
5. "It is scientifically incorrect to say that war is caused by ‘instinct’ or any single motivation."
Hauser Chapter 1. Nature’s secrets 40
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