Having a 7-year-old and a 4-year-old, it’s easy to ask the question “Why did you do that?” If I had super brilliant kids, they might respond, “My genes made me do it.”
There are a lot of things that we think we control or decisions we think we make that are really rooted in evolution. Take for instance this quote from Stephen Pinker’s How The Mind Works which could be titled “Oh Cheesecake, Why Do I Love Thee So … Even As You Pad My Belly With Fat?”:
We enjoy strawberry cheesecake, but not because we evolved a taste for it. We evolved circuits that gave us trickles of enjoyment from the sweet taste of ripe fruit, the creamy mouth feel of fats and oils from nuts and meat, and the coolness of fresh water. Cheesecake packs a sensual wallop unlike anything in the natural world because it is a brew of megadoses of agreeable stimuli which we concocted for the express purpose of pressing our pleasure buttons.
Cheesecake itself is not good for us, but each of the elements of cheesecake would have been strongly beneficial to our ancestors. Now that we’ve settled that one, what other questions can evolution help us with? How about this one, “Are Humans Monogamous?”
Robert Sapolsky, in his Great Courses Series, Biology and Human Behavior: The Neurological Origins of Individuality, uses biology to answer this question. Sapolsky divides species into 2 types: tournament species (polygamous) and pair bonded (monogamous). In a tournament species, males spread their genes by mating with any females around. Once they pass along their genes, they abandon their mate and look for someone new. Pair bonded males bond for life and are very paternal.
There are clear traits that call out how each species has evolved. In a tournament species, males are built for fighting. They are much larger than females, have huge canine teeth and much larger skulls (but not brains) than females. They often have weapons like giant antlers. Females, not looking for a fight, look very different from the males. In pair bonded species males and females look much more similar.
So what are humans? Based on the physical markers, males and females are relatively equal in appearance. Males have large canines but not huge. And men are bigger than women but not terribly so. So the biological answer is that humans aren’t polygamous or monogamous. The official classification for homo sapiens is “tragically confused.”