Are the majority of your ancestors farmers or non-farmers?
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85My initial intuition was "surely there were more non-farmers", but I did some calculations and it looks closer than I thought.
I had a go at a guesstimate model, where I estimate the number of humans who lived in each period, the % of them having offspring, the chance that I descend from them, and an estimate % who are farmers in each period.
I get 11 billion non-farming ancestors, and 4.6 billion farming ancestors (around 3.6 billion exclusively/mainly farmers).
What I see as the "crux period" is 0 BC - 1200 AD; I can't find any data how many of the humans in that period are likely to have been my/your ancestors. I've put 15-40%, but if it's closer to 60%, farmers might edge it. Also, I haven't accounted for lineages ending - aside from individuals not having offspring (which I take as a constant in the model), there may have been some huge lineage collapses, presumably more before farming than after.
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The question very specifically asked for starting 300,000 years ago, not 10,000.
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This seems very surprising/wrong to me given my understanding of the animal kingdom, where various different bands/families/social groups/whatever precursor to tribes you think of have ways to decrease inbreeding, but maybe you think human hunter-gatherers are quite different? I'd expect population bottlenecks to be the exception rather than the rule here across the history of our species.
I'd trust the theory + animal data somewhat more on this question than (e.g.) studies on current uncontacted peoples.
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Sorry, just read this response.
On the intuition question, my intuition was probably the other way because most of human history was non-farming, and because the vast majority of farmers (those born in the last millennium) weren't my ancestors.
I updated my model to account for an error - it's now a bit closer. 7.8 billion non-farmers to 6.4 billion farmers, and 4.9 billion exclusive farmers, but I still basically stand by the logic.
To respond to your question, why I didn't pick a fixed number of personal ancestors:
We have fewer recent ancestors, assuming 16 generations, we'd have around 20k to 50k ancestors at 1600. (2^16 - inbreeding). If we want to count these ancestors carefully, we should count back with an algorithm accounting for population size and exponentially increasing inbreeding.
We could also plausibly try to use this strategy to draw a more accurate number of ancestors from 1200-1600--- this might be a period where individual/geographical differences, or population constraints, play a significant role. If you're Icelandic, most of your ancestors in this period will still be from Iceland, but if you are Turkish, your ancestors from this period are more likely to extend from Britain to Japan. My model doesn't do this, because it sounds difficult, and because the numbers are negligible anyway- I just estimate that 0.1% to 1% of total humans born from 1200- today were my ancestors.
By around 1200 AD, it surely becomes impractical to rely on a personal family tree to track ancestry, because of the exponential growth in the number of ancestors. Beyond that point, your total potential ancestors (in the billions, without factoring in inbreeding) massively exceed the global population (in the 100s of millions). The limited population size becomes the constraint.
So an Italian might assume that they are descended from a significant portion (40%?) of Europe’s population in 1200 AD. By 800 AD, this would extend to a majority (60%?) of people living
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Well, you can stick your own numbers into the model and see what you get - a few tweaks in the estimates puts farmer ancestors higher, as would assuming more prehistoric lineage collapses.
For example, if you think that almost everyone who had offspring from 2000BC-1200AD was your ancestor, then you get more farmer ancestors. I initially put it closer to 40% (assuming little to no Sub-Saharan or Native American ancestry, and a more gradual spread throughout Eurasia), but the model is sensitive to these estimates.
From a "Eurasia-centric" perspective, my sense is that personal ancestry doesn't make a major difference except for pockets like Siberia and Iceland, perhaps. It's noticeably different for people with some New World or Sub-Saharan ancestry, and wildly different if you're pure-blooded Aboriginal Australian.
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I explained why I think tracing back personal history is impractical.
Your separate method to spot check my model is just a simplified version of the same model.
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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".
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I would expect that if we go back 1000 years, then all Eurasian farming humans alive at that point are your ancestors.
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A sensible question would weight ancestors by amount of shared genes.
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If you disagree with the question, why answer deep in the comments of one answer than at the top level?
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By sensible, I don't indicate disagreement, but a way of interpreting the question.
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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.
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.
This was not my question, but you're free to answer a different one! :)
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Ahh, but without a purpose, how can one tell what the question actually is?
You could be asking about who you get by tracing back births and matings over the last 300,000 years that led to you. But do you then count people more than once if they show up more than once in this back trace?
Or are you really asking where your genetic material came from? It's quite possible that none of your genetic material came from one of your great-great-great-great-great-great-great-grandfathers. Genes aren't selected independently to be included or not in sperm or egg, but instead come in larger chunks (I think a few hundred of them), which means that it's entirely possible for the entire genetic contribution of one "ancestor" to by chance be lost in relatively few generations (of course, that means that some other ancestor contributes more than one might have thought). If you define "ancestor" as "person some of whose genes I have", then the number of distant ancestors you have is much less than you might have thought.
In the above, I'm tracing back where from a physical point of view the genes came from. But of course, the fact that the genes of some ancestor did not by a physical process result in any genes in you does not imply that you don't have some of the exact same genes as them - which you may have obtained from some other ancestor. Does that count?
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Not every question has to have a purpose! :) Imagine that this is intellectual interest only, at least to me.
No? This question would be trivially easy if you did lol.
No. I personally wanted a literal answer to my literal question.
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In that case, it's non-farmers by a good margin. Our ancestry goes back well over a billion years, mostly in species with short generation times. Farming goes back roughly ten thousand years in a single species with a ~25 year generation time.
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The question specified the restriction to humans in the last 300,000 years.
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I'm confused about the disagree votes. Which specific sentence do you disagree with?
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Note you can now line-item react to highlight specific disagreement!
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Very cool!
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 (...
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One thing to consider is that we have more female ancestors than male ones, because males are far more likely to fail to breed, while also having the option to be much more successful breeders.
And historically, men were far more likely to be farmers (in a literal sense, farming plants being their main occupation, lifestyle and a source of calories) than women.
Or to put it differently: between about 12000 BC, and about 1800 AD, there majority of women were WIVES of farmers, but not farmers themselves (due to division of labor, the vast majority of women did jobs related to the production of cloth and non-farmign products, while men did the farming), while at the same time, there was a big % of men who were farmers (often unfree to some degree) who died childless.
Moreover, farmers usually stayed on the same land for a long time, intermarrying with their neighbors, thus particularly virile farmers eventually became ancestors to a lot of their neighborhood, while unsuccessful, poor, or unfree farmers had few or no children.
Women, moreso than men, would marry-out and leave their ancestral household, thus spreading their genes.
So we might end up with a calculation where you have a lot of Spinner and Weaver ancestors, but fewer Farmer ancestors.
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According to this, there were only 9 billion humans alive before the agricultural revolution, as compared to 109 billion who have lived and died:
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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.
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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.
Or are we thinking that it gets weirder when you account for population size expanding after farming?
Yes. Keep in mind that there's like an order of magnitude more people post agricultural revolution.
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That does make it more difficult. Order of magnitude (or more) more people in each generation after farming, but more than an order of magnitude more years in the period before farming.
The "if you go back far enough, everyone was your ancestor" argument only kicks in part way through the farming period whereas it would be in full effect for pre-farming. But also probably a greater proportion of hunter gatherers died without leaving any descendants, or have had their line of descendants die out in the time since.
Ok, you've successfully induced uncertainty. I don't feel able to do math to come to a clear answer.
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'Pedigree collapse' happens shockingly fast. You apparently do not have to go back more than 1-2000 years before everyone shares a common ancestor and the pedigrees are all linked. So, you will have pedigree collapse in your local population well before that. This means that your particular ancestry can't matter much (since soon you'll share the same total population of unique ancestors as everyone else), only the ratios of ever-farmers:ever-nots over the total human population history. Since the non-farming lifestyle only supports on the order of millions of humans rather than billions of humans, the ratio is pretty decisive. Farming just supports much, much, much larger populations of humans, and thus, ancestors. As long as you are not too close to the Neolithic (as we are not inasmuch as farming began ~11,000 years ago), I would expect the exponential rise of the farming human population to have long ago reduced your hunter-gatherer ancestry to some extremely small percentage of 'all your ancestors' like 1%, and thus extremely far from >50%.
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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.
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Yamnaya ancestry (Indo-European steppe-pastoralists) make up a large percentage of European genetic ancestry. Modern Europeans are a mixture of three ancestral populations: steppe-pastoralists from the east (Yamnaya...), Western huntergathers, and Anatolian farmers. In some Northern Europeans, the fraction of farmer ancestry may be less a minority.
"Yamnaya–related ancestry is found in the DNA of modern Central, and Northern Europeans (c. 38.8–50.4 %), and is also found in lower levels in present-day Southern Europeans (c. 18.5–32.6 %), Sardinians (c. 2.4–7.1 %), and Sicilians (c. 5.9–11.6 %).[80][71][13]"
https://en.wikipedia.org/wiki/Yamnaya_culture#:~:text=Yamnaya%E2%80%93related%20ancestry%20is%20found,%25)%2C%20and%20Sicilians%20(c.
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Okay, assuming this means "how many Homo Sapiens ancestors did you have that spent substantial amounts of their working life farming", I think every human being alive has around 25x more non-farmers than farmers as ancestors. I think the ratio is so large that the answers doesn't change even if you ask "how many ancestors lived in agricultural societies" instead of "how many ancestors were farmers" and regardless of where your ancestors were - even comparing people whose ancestors were all in a place that invented agriculture early vs someone whose ancestors didn't start farming until after the industrial revolution.
The only thing that matters, to the extent that it swamps every other variable, is how long humans have been farming. Per Wikipedia, Agriculture developed in multiple places around the world after the last Ice Age, ~10,000 years ago. Homo Sapiens is about 30 times older evolving ~300,000 ago. The number of years your ancestors could have possibly been farmers is a rounding error compared to that.
I don't think changing generation length matters much - it's probably between 15 and 30 years for basically all your ancestors up to the modern day, nowhere near the ratio it would need to make a difference to the answer. Pedigree collapse (some of your ancestors show up in multiple places in your family tree, moreso the farther back you go) matters, but again it can't possible swamp the ~30x difference in number of generations. And, at the very least, you're guaranteed to have at least 2 ancestors per generation.
This is a great question, thanks for posting it!
Why do you think pedigree collapse wouldn't swamp the difference? I think that part's underargued
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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.
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23&me says I have more Neanderthal DNA than 96% of users and my DNA attribution is half-Japanese and half European. Your Neanderthal link doesn't work for me.
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That's interesting. On the recent episode of Dwarkesh Podcast with David Reich, at 1:18:00, there's a discussion I'll quote here:
Now I don't know which paper this is referring to but it's interesting nonetheless.
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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.
If we count how many people dead or alive are you related to. Farmers.
Why? This is extremely non-obvious to me. There are ~290k years between 300k years ago and the approximate start of the agricultural revolution.
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Note that post-industrial revolution ancestors are mostly a red herring, almost all of the action is figuring out whether you have had more ancestors before agriculture vs after.
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.