Assume humanity began with homo sapiens ~300,000 years ago. Are the majority of your ancestors farmers or non-farmers?
My friend and I had very differing intuitions on this, and after thinking about it some, both of us currently think it's very non-obvious.
Providing a sensible answer is dependent on arriving at a sensible interpretation of the question. I'll assume that it is aimed at understanding to what degree farming or non-farming lifestyles have had an influence on the selection of genes that you carry. I assume that "farming lifestyle" includes people who don't actually farm, but obtain food from farmers, one way or another.
On that basis, and assuming you are a typical inhabitant of a society that hasn't recently engaged in much hunting/gathering (maybe some fishing, but not dominant), I would say that about 1/30 of your ancestors were of a farming lifestyle. That is, if you trace back what the selective influences were on your ancestors, about 1/30 of it was selection for reproduction in a farming community. I get the 1/30 by dividing 300,000 years of homo sapiens into 10,000 years of agriculture.
I don't think the population sizes at different times, and collapse of the pedigree (some of your ancestors being the same people), make any difference. It might make a difference if the number of children per person varied, since each child is a new object for selection, but I think this may be rather constant until very recent times. And of course, the number of children who survive to reproduce themselves is close to two at all times. (The population has grown over time, but at nowhere near the rate it would if, say, three children per couple survived to reproduce themselves.)
Now, depending on how quick evolution can act, the fact that the 1/30 of the selection influence is the most recent 1/30 could be crucial.
Now, depending on how quick evolution can act, the fact that the 1/30 of the selection influence is the most recent 1/30 could be crucial.
This is an important insight, if that's the reason behind the question. If you break one's genetic heritage into 30 equal slices, 29 of which are hunter-gatherer, one of which is farming, and the last fragment is a rounding error too short for evolution to matter. You'll likely find that evolution is punctuated by reactions to large changes in what makes for fitness in the environment. The first slice (...
Wikipedia suggests an average of 50,000 individuals for prehistoric humans in Africa. Population sizes after farming were so much larger, that I would expect the majority of my ancestors to be farmers.
Ah but your "ancestors" means every individual who contributed to your genetics. If "humans" existed for longer as hunter gatherers, even if there were far fewer of them, then far more generations of individuals contributing to your existence would have come from them.
Gwern points out below that since at a certain point we all share common ancestry, only ancestors who can be considered "different" can count as an "ancestor".
Populations got much bigger post-Industrial revolution, after which very few people were farmers. I'm pretty sure more people who have existed were non-farmers just from that growth, by a huge margin.
But I'm not sure whether or not that should carry over to ancestors. On one hand, you can only have so many ancestors at a time, and explosive industrial population growth doesn't change that. But smaller farming populations might mean more of my family tree crossing over itself, and so fewer unique farming ancestors?
I'm pretty sure more people who have existed were non-farmers just from that growth, by a huge margin.
This is wrong, if we date the Industrial revolution to ~1750. According to this article, the halfway point for "number of humans who have ever lived" is likely before 1200 CE.
I would expect the general breakdown to be a few recent generations of maybe not farmers, several thousand years of mostly farmers, and then the remainder of the time between the dawn of humanity and the beginning of agriculture being "farmers didn't exist yet".
Exactly when agriculture began isn't an entirely settled question, but there doesn't seem to be any suggestion that it was early enough to make up any more than a small fraction of the last 300k years.
Even if you include some proto farming, like a hunter-gatherer occasionally choosing to scatter seeds in a convenient foraging spot, I don't know if you get back to 150kya (or whenever the halfway point would be when accounting for changing generation times, and counting ancestors rather than years)
Or are we thinking that it gets weirder when you account for population size expanding after farming? That would provide more people to be distinct ancestors (past a certain point, everyone who was alive at the time either has no living descendants or is a universal ancestor), but I'm dubious of that out weighing the long (long) period of pre-farming.
Linch, unless you are African then you have 1% to 4% Neanderthal genes, there was interbreeding and presumably we had "mixed" individuals on both sides. Neanderthal (and Denisovans etc) must have had similar levels of consciousness to us so there would have been an exchange of culture. Homo Sapiens are not your only ancestors.
I'm East Asian, which likely means significant Neanderthal and Denisovan influence.
Hmm well I also have small mammal and bacteria ancestors, presumably. So we need a cutoff somewhere. But I guess with my (arbitrary) cutoff of 300K years ago, I'd also be happy to include the non-Homo sapiens ancestors, not that it's very likely to flip the final answer.
According to this, there were only 9 billion humans alive before the agricultural revolution, as compared to 109 billion who have lived and died:
If ancestor is parent/mother/grandparent etc but nothing else. Obviously non hunters.
If we count how many people dead or alive are you related to. Farmers.
So, figure 25-year generations (probably too long, but this is a Fermi estimate at best), so humanity began 12000 generations ago. If you assume no consanguinity (definitely false), going backward in time each generation has twice as many of your ancestors as the previous (in counting, next in time) generation.
There have not been 2^12000 people at any point in history, or even in the sum of history. Which means we need to add some complexity. Probably a LOT of merges in that family tree (meaning it's a family directed graph, not a tree :). Far enough back, it probably stabilizes at a few hundred each generation (meaning: effectively all pairings are (perhaps distant) cousins, so ancestors are multiply-pathed and not added at each generation). But that's likely too constrictive. You get to make a modeling choice how you want to calculate that expansion.
And that modeling choice overwhelms most of the rest. So you have to figure out what elements are important to get right, and what expected experience you're trying to predict. How will this bet resolve? What will happen if you're closer to correct, vs further?
In my world, where nobody cares about the answer, but I get meaningless points for sounding smart, I'll either refuse to answer (as above), or be super-simple and say "ancestor "width" probably stabilizes at some point less than a few thousand years back, so this is likely close to "how long was humanity mostly farmers vs mostly non-farmers". Which is roughly 1/25 of the total human existence.
I would expect the general breakdown to be a few recent generations of maybe not farmers, several thousand years of mostly farmers, and then the remainder of the time between the dawn of humanity and the beginning of agriculture being "farmers didn't exist yet".
Exactly when agriculture began isn't an entirely settled question, but there doesn't seem to be any suggestion that it was early enough to make up any more than a small fraction of the last 300k years.
Even if you include some proto farming, like a hunter-gatherer occasionally choosing to scatter seeds in a convenient foraging spot, I don't know if you get back to 150kya (or whenever the halfway point would be when accounting for changing generation times, and counting ancestors rather than years)
Or are we thinking that it gets weirder when you account for population size expanding after farming? That would provide more people to be distinct ancestors (past a certain point, everyone who was alive at the time either has no living descendants or is a universal ancestor), but I'm dubious of that out weighing the long (long) period of pre-farming.
OWID claims that there were ~9 billion people, or about 8%, of people before the agricultural revolution. So I don't think you can get to quite as low as ~1%.
If we make the simplifying assumption that everybody in the past are ancestors, then we get 8% non-farmers. This assumption is ofc false, but if it's true across a fairly small number of generations, farmers will outweigh non-farmers as you say.
According to this article, the halfway point for "number of humans who have ever lived" is between 1 CE and 1200 CE.