Pair bonding
These are mainly notes to myself so that I retain what I read.
Monogamous relationships seem so natural to us, but we are actually the only species of primate to do this. Our closest cousins, Chimpanzees are intensely territorial and compete intensely for mating rights, with the chief male and his lieutenants siring nearly 50% of the band’s children.
How did pair bonding evolve to become a survival advantage?
Some millions of years ago, probably 5ish or so, when the environment cooled and became shit, a group of apes left to trees to try their luck on the ground even though they could be pounced on by big cats and other crazy shit. Those who stayed on trees became ancestors of chimps while the group that left became our ancestors.
A couple of things happened to apes on the ground.
- They started walking on both feet because it was more efficient than dragging their knuckles around. As a result, this freed out their hands to carry stuff and eventually create tools. Tools eventually became weapons which allowed us to not just hunt better, but became great equalizers of size and strength in mating competitions. Because of this, male size and aggressiveness (which bears a heavy cost in calories) was no longer an evolutionary advantage and average male size relative to females shrunk.
- Males spent more time “mate guarding” (guarded their mate from procreating with other males — all primates do this to some extent), partially because of dangerous predators on the ground. As a side effect, the males helped out with raising the kid, allowing babies to be born earlier and in a more vulnerable state, but whose brain would grow in the world, and learn.
Female chimps leave their territory when they become juveniles, so if you imagine growing up as a chimp baby, you’d know your mother and probably some of your siblings who were boring within a few years of you. But you don’t know your father and his side of the family. So when the neighboring band of chimps invade to kill you, they’re likely to be close cousins.
With pair bonding, our human ancestors knew both sides of the family, and being close to both sides of the lineage, neighboring bands instead formed larger groups known as tribes. Sure, inter-tribal warfare was just as fierce as chimp bans fighting, but with group conflict moved up to the tribal level, human ancestors planted the seed for larger group co-operation.
Scientists don’t think pair bonding became close to its modern form until the rise of Homo Ergaster around 1.8 million years ago, where bones of hominin families were found together.
Pair bonding is just one example of our social behavior being formed by evolution. Behaviors that were advantageous to natural and sexual selection survived were passed on in genes. These play into our culture, which then forms the institutions of which we are governed by. This raises an uncomfortable question… could this explain how some parts of the world never rise from extreme poverty as the social behavior of their inhabitants, and the institutions that they build, were formed on the foundations of genetics? How much exactly is this genetic influence? Surely, environment influences it with the discovery of epigenetics.
Big questions ahead.
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Working through the 1st few chapters of Nicholas Wade’s A Troublesome Inheritance: Genes, Races And Human History. Will write continously as I get through it.
