The strong Grandmother Hypothesis

(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: lawrence@krubner.com

I was never a hunter, but when I was 20 I loved to explore forests. I’d go into the forest for days, and explore areas where I thought other folks had not been in a while. I was mostly on the east coast of the USA so I did not have to worry too much about bears. When I was out West I had some close calls with bobcats, but I was lucky.

Young men typically go on adventures into the wilds, to test themselves and to learn about the world. And there are men who are much more adventuring than I.

According to Ian Tattersall, modern homo sapiens arise around 200,000 years ago, somewhere in the region within a few hundred kilometers of Lake Victoria.

But Tattersall, and others, agree that homo sapiens first cross over to Saudi Arabia around 150,000 years ago, crossing by water at the southern most point, near Yemen.

For a healthy young man, even on a slow raft, it takes a few weeks to get from Kenya to Saudi Arabia. It does not take 50,000 years. Trying to explain why this expansion would take so long is an interesting thought experiment. Here are some ideas:

1.) War — there was so much fighting among human tribes that no one had any time to go on a fun expedition. Even when homo sapiens were few, the world was thick with humans of other species. As someone has pointed out (can’t remember who but I’ll edit this when I find the reference) since humans were a successful mammal group, and since bison were a successful mammal group, and at this time bison numbered 100 million, it seems likely the world had 100 million humans at this time. Not homo sapien, but humans. That’s already a lot of humans contend with. But it would stop young men from adventuring. If anything, it gives them a stronger motivation to try to find some uninhabited land.

2.) Fear of new foods and poison — this did not stop me from taking risks when I was in my 20s and it certainly wouldn’t stop the young men of 200,000 years ago, who basically had to devote their lives to figuring out what was safe to eat, since there was no grocery store where they could go and get “safe” food.

3.) Expansion in other directions — maybe lots of young men went exploring, but they simply preferred to explore the interior of the African continent, rather than it shores. This seems like a completely reasonable explanation for shorter periods of time, but not 50,000 years.

4.) Why should there be any expansion at all? — this is related to the question “Why should we assume economic growth is automatic?” And this is roughly what I expect the answer to be. Homo sapiens were not necessarily so adaptive that their growth should have been automatic. Sometimes yes, and sometimes no. They expanded, then they contracted, just like now. But what were some of the limits on that growth?

5.) Everything is great so why go anywhere? — this must have also been true, at least some of the time. There was plenty of awesome hunting to do where they were, so why go anywhere else? Life’s a party, so why stress about moving the tribe elsewhere? Whenever homo sapiens find a mix of politics and technology that is especially adaptive to their current circumstance, they feel that life is a party. That would have been as true 200,000 years ago as it was in the 1960s. (This is a strong version of the notion that there is a maximum utility that humans can experience.)

I suspect that, starting around 200,000 years ago, young men on “vision quests” often left Kenya and went up to Saudi Arabia or Persia, or even farther. Some of them settled down with non-homo sapien humans and married and never went home. Others did go home. But moving the whole tribe is what took 50,000 years. And of course, it wasn’t the ancestral tribe, but some new branch of it, which grew up thanks to an expanding population.

But why not grab a girlfriend and take her with you? Possibly you could, but she’d have children, and without help, the children would die out. So all the couples who did this ended up living in Saudi Arabia with very few children. If we assume, as I do, that hyper-fertility is the main advantage that homo sapiens had over other human species, then the boyfriend-girlfriend combo who went alone to Saudi Arabia would have had no advantages relative to the other human species they found themselves in competition with.

Which brings us to grandmothers. The Grandmother Hypothesis says:

The grandmother hypothesis is a theory to explain the existence of menopause in human life history by identifying the adaptive value of extended kin networking. It builds on the previously postulated “mother hypothesis” which states that as mothers age, the costs of reproducing become greater, and energy devoted to those activities would be better spent helping her offspring in their reproductive efforts. It suggests that by redirecting their energy onto those of their offspring, grandmothers can better ensure the survival of their genes through younger generations. By providing sustenance and support to their kin, grandmothers not only ensure that their genetic interests are met, but they also enhance their social networks which could translate into better immediate resource acquisition. This effect could extend past kin into larger community networks and benefit wider group fitness.

The strong version of this would be that human expansion was impossible without grandmothers. So that implies that homo sapiens expanded, not at the rate preferred by 20 year old men, but at the rate preferred by 60 year old grandmothers.

The strong version of this therefore implies that grandmothers are the driving force of the genocidal process whereby one human population replaces another. Although killing strangers is mostly a male monopoly, most actual genocide is not done by killing people, it’s done by depriving them of the land where they can get food or water. More so, since most genocide plays out over the course of generations, one could say that grandmothers are the people responsible for creating the “reinforcements” who will fight the next round of battle. I’m tempted to believe this, because it fits what I know about people — that is, people are terrible, and they seem way too comfortable with the quieter forms of genocide — among my peers, suggesting we put a racial group in a gas chamber is very rude and violates all kinds of social norms, but suggesting we take half the men, of some racial group, and lock them up in prison for 10 to 20 years, is perfectly acceptable.

And I think everyone knows that grandmothers are quietly murderous.

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