Tribal war drove human evolution of aggression
Wars are costly in terms of lives and resources - so why have we fought them throughout human history? In modern times, states may fight wars for a number of complex reasons. But in the past, most tribal wars were fought for the most basic resources: goods, territory, and women.
These reproduction-enhancing resources prompted our ancestors to fight in order to pass down their family genes. With war as a driving force for survival, an interesting pattern occurred, according to a new study. People with certain warrior-like traits were more likely to engage in and win wars, and then passed their warrior genes down to their children, which - on an evolutionary timescale - made their tribe even more warrior-like. In short, humans seem to have become more aggressive over time due to war's essential benefits.
In their study, Stanford University scientists Laurent Lehmann and Marcus Feldman have presented a model showing that aggressive traits in males may have evolved as an adaptation to limited reproductive resources. Because tribal war serves as a method for appropriating territory and women, war may have driven the evolution of these traits.
The scientists use the term "belligerence" to refer to a trait that increases the probability that the person's tribe will attack another tribe. Likewise, "bravery" refers to a trait that increases the probability that the person's tribe will win a war, whether they have attacked or are being attacked.
Lehmann and Feldman demonstrate in their model that belligerence and bravery continue to genetically evolve through the male line. When one tribe conquers another, males in the conquering group mate with females in the conquered group, and pass the warrior traits to their male offspring.
"Suppose that for some reason or another each individual in a population is committed through genetic or cultural influence to go to war with probability 0.5," Lehmann told
PhysOrg.com. "Now in one group...
