Humans Evolved to Fight

The following article is based on a the 25 April 2009 episode of Quirks & Quarks on CBC radio.
Chimp Thinking About Violence
Mixed Martial Arts (MMA), otherwise known as “Ultimate Fighting” is the fastest growing spectator sport on television. Many find it the most exciting thing to watch. Stage combat is often the most engaging part of a night at the theatre. And any observer of current events or the history of the human race can attest that we excel at doing violence to each other. So we perform it, and we enjoy watching it.

Why? Is it biological or cultural?

Do our ancestors share our violent tendencies?

The Violent Time Machine

We can look at chimpanzees to see what our evolutionary forebears would have done. Jane Goodall watched the chimps, and noticed that they had clear territories, and when they got near another tribe’s border, they would shout at each other and occasionally charge, but don’t actually fight very often. So although they intimidated members of other groups, they were relatively peaceful according to these early observations.

By the 1970s, the view of chimps changed. Researchers witnessed a kidnapping of an infant chimp by a neighboring tribe. The baby was murdered, and then brought back to the center of their range. Then in 1974, a small party of chimps invaded the adjacent territory and found a male eating alone. They sneaked up to him and ambushed him, beating him so badly that he died within two days. Further study revealed that this was not a rare behaviour.

Human hunter-gatherer tribes seem to behave in similar ways. It makes sense. The best way for most animals to have healthier lives is to have more food. For territorial animals like chimps and humans, that means expanding territory. In order to do this, the larger males must intimidate or overcome the neighbors. And this leads to a systematic killing of males. Each male killed is a significant shift of power in small tribes.

Have we evolved away from this behaviour?

Bipedalism: Not Just For Walking Anymore

The standard anthropological argument was that we developed bipedalism because it was better for walking on the ground, as compared to using all four limbs in the trees. When it became apparent that we aren’t great walkers, some researchers changed their theories and claimed that humans are optimized for running long distances.

There are no clear advantages to walking or running bipedally for an organism that is already adapted to walking on four legs. Just try to outrun a dog sometime, you’ll quickly find who has the energy advantage. But what makes sense is that if you fight with your fore limbs rather than your mouth, it’s better to be able to balance and move well on two legs.

The longer your legs, the better walker or long-distance runner you are. For examples, look at the olympic champions in the marathon and the walking races. If we were evolving bipedalism in order to walk, we should have evolved longer legs. However, we kept short legs in Australopithecus because walking wasn’t the point: you fight better standing on two short legs.

Modern Humans Can’t Fight

But we don’t look like we’re built to fight. Humans do not have claws or fangs. We’re not as strong as gorillas, or even chimps (pound-for-pound). But we have big palms, big thumbs, and shorter fingers. Good for tool use? Yes, but longer fingers would be better. You know what our proportions are good for? Making a tight fist. Other primates can’t do it. All apes can grasp objects and hold them tightly, but only the human can form a fist to punch with.

But anatomy is versatile, and we can’t infer that any structure was designed for a purpose, only that it evolved and natural selection didn’t find anything better. So what other evidence can we find?

Know Thy Enemy

Most social animals can assess fighting ability in others of the same species without actually fighting. They may dance or display or just observe, and the weaker party walks away. Do humans have the ability to assess fighting ability without fighting? Yes. A recent study demonstrated that subjects who were shown an image of a face only (even the neck was digitally removed), they could accurately rate how strong the person was.

It is likely to be due to the effect of testosterone on the facial structure. High testosterone gives you more muscle mass, more aggression, plus that “caveman” look: big eyebrow ridge, wide jaw. It’s what we try to imitate when we make an angry face. Even people blind from birth make this face when angry: eyebrows flexed downward and together, corners of the mouth down-turned. This pushes more flesh into the areas that would be bigger if you had more testosterone. It’s just like a cobra’s hood, or your dog hunching his shoulders and raising his back-hair. It makes them look scary.

Do our brains work differently than those deadly animals?

Aggression Is Its Own Reward

Mice enjoy punishing other mice. You can make a mouse learn a trick by rewarding them with food. You can also train them to perform the same trick by making the reward an opportunity to attack another male mouse. No extra food, just aggression. They get a feeling of satisfaction from a release of dopamine in the brain when that happens. It’s the reward center of the brain, the same thing happens with heroin.

When men are shown violent videos, they get the same rush of brain chemicals as when they’re shown sexy videos as observed in functional magnetic resonance imaging (fMRI). So that means that, like the mouse, adult humans get a dopamine reward and feel pleasure from watching violence just as much as sex.

Recent Developments in Peace

The good news is that things are actually improving in our daily lives. Many people believe that the 20th century has been the bloodiest ever, marked by more wars and more death than ever before. In raw numbers, this is true. However, the proportions of violent deaths has been declining rapidly. Each war has seen fewer casualties.

The best part is that our daily lives are devoid of violence for most of the population. I don’t mean to marginalize those unfortunate people who live in warzones, but the truth is that those that fear for their lives on a daily basis are very few. Not long ago, the human race was living like those chimpanzees: raiding neighboring tribes, and losing fighting men every year. So maybe watching MMA and great stage fights is an acceptable alternative to the human losses we suffered in the past.

Leave a Reply