One of the authors of this paper, David Reich, has written a book called "Who We Are and How We Got Here", which is worth reading. My thoughts on it: https://www.goodreads.com/review/show/2605841954
The dataset excites me more than the fairly vague conclusion that some SNPs possibly linked to traits were selected for (or hitched along to genes which were selected for). Genetic archaeology is just so much more exciting than this.
But I bet there will be a ton more of that too, thanks to the high quality dataset.
> the fairly vague conclusion that some SNPs possibly linked to traits were selected for
Interesting. I find that part of the paper the most exciting. We always knew selection would happen for valuable traits. But seeing demonstrations of it in the timelines we have is pretty important.
This study covers about 10,000 years of recent human evolution in Europe and West Asia.
From the abstract:
>in the past ten millennia, we find that many hundreds of alleles have been affected by strong directional selection. We also document one-standard-deviation changes on the scale of modern variation in combinations of alleles that today predict complex traits. This includes decreases in predicted body fat and schizophrenia, and increases in measures of cognitive performance. These effects were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past. We estimate selection coefficients at 9.7 million variants, enabling study of how Darwinian forces couple to allelic effects and shape the genetic architecture of complex traits.
> We finally observed signals of selection for combinations of alleles
that today are associated with three correlated behavioural traits:
scores on intelligence tests (increasing γ = 0.74 ± 0.12), household
income (increasing γ = 1.12 ± 0.12) and years of schooling (increasing
γ = 0.63 ± 0.13). These signals are all highly polygenic, and we have
to drop 449–1,056 loci for the signals to become non-significant
(Extended Data Fig. 10). The signals are largely driven by selection
before approximately 2,000 years )*, after which γ tends towards zero
Presumably pressure in different regions lead to different combinations of those alleles, which I think they are shorthanding a bit, but the fact that those alleles exist makes blank slate theory a kind of rough assumption
No, this paper doesn't seem to talk about regional differences. The implication seems to be that it wouldn't be surprising to find differences between groups that separated more than 2kya, as there was active changes going on before that time. Not that it predicts any specific differences
> If anything they seem to support homogenization of intellectual capacity/mental health in Eurasia since 2kya.
I would be interested in how you came to that conclusion, unless I'm misleading your post and you specifically mean West Eurasia
> Just because an allele, SNP, or trait swept into or out of West Eurasia during this time doesn’t mean this happened only in West Eurasia. Researchers can use the new computational methods to look for directional selection in other populations worldwide that have enough ancient DNA sequences and construct a clearer picture of what’s unique to different groups and what generalizes across populations.
> Reich expects that future studies will show that shared selective pressures acted on some of the same core traits across diverse human groups, even as those groups split off and migrated to different parts of the world over tens of thousands of years.
There is a graph arguing “intelligence” has been positively selected in west Eurasian population in this paper according to a polygenic score (page 8 fig. 4)
Now I would be quite curious to know how they constructed this polygenic score
To be clear: most people who are keen on making such an argument, or who are identifying racial genetic differences as the primary takeaway of studies like this, are doing so to justify racism, either implicitly or explicitly.
But that's a strawman. Racism is wrong, even if there are minor genetic variances across populations (which... seems obvious?) Variance within a population strongly dominates the weak cross-population effects, and personal history (nutrition, education, etc) strongly dominates that.
And that's setting aside the moral implications of judging someone or changing your behavior towards them even if you have somehow measured them to be "less intelligent," as if that was a single axis of worth.
> most people who are keen on making such an argument, or who are identifying racial genetic differences as the primary takeaway of studies like this, are doing so to justify racism, either implicitly or explicitly.
That may certainly be true.
(Not OP, but) I always shutter when we want to deny scientific results because it might be "helpful" for someone making a racist argument.
My personal belief is that truth is the goal of science. Even in cases where the truth is uncomfortable.
It's very nice to believe in a pure system that exists outside of politics, but that's simply not how the world works, and it never will be.
There is no scientific breakthrough that has occurred sans politics. Politics choose the winners and the losers, and the realm is science is no exception.
All science is political, because the scientific institutions are made up of people, who are political. Your research project lives and dies by politics, as does your dissertation, who gets published, who receives awards, etc.
So when it comes to research of limited utility that has a nasty cadre waiting in the wings to pounce upon it, the wise person would think twice.
As I said to another person on this thread: if scientists let their political views override their pursuit of truth, the public will (rightly) lose faith in science.
So when you tell them to "trust the science" -- be it vaccinations, climate change or something else -- they have no reason to trust that science.
There are a few scientific topics that are too easily manipulated by bad actors who ignore all the nuance. You have to tread very, very carefully on those and ask yourself what good vs. what harm can come from it. We know from history that giving opportunist leaders a chance to classify humans into distinct sub-groups based on intelligence and other key traits ends in catastrophe.
I understand what you are saying and I don't disagree with the idea that bad actors will use science in bad ways.
But I think going down this path of denying (or hiding) science that can be used for bad ideas ends up causing (rightly, imho) a distrust of science -- which is far worse.
A distrust of science (not saying it was caused by this particular issue) is how we ended up with so much anti-vax sentiment in the US. And that is the reason we are seeing outbreaks of diseases that used to be minimal.
I think if you want people to "trust the science", you have to trust the people.
This interest in IQ has a negative effect on the concept of intelligence, never mind human unity. It attaches exaggerated importance to test scores, jobs, and school. It tends toward snobbery.
I think the discussion in recent years has refocused, embracing ethnonatalist implications and challenging the core assertion that "racism is wrong".
My main resistance to that is much the same as yours: the differences are so small, that re-architecting society around them is not going to be enough juice for the squeeze.
But one could also argue that the juice is not even the point: by re-architecting society in this way, you "pre-brutalize" your population so that their threshold for violence against "others" is lowered. Thus your population is closer to being wholly militarized, and theoretically is more effective in war, and is less captured by "weak" or "unmanly" moral ideals, such as empathy.
While this might seem a virtue to someone of an expansionist mindset, in application this principle never, ever works well - again, thanks to those tiny differences. If a citizen is pre-brutalized to have a lowered resistance to killing those with curly hair, how long is it before they kill their next door neighbor with wavy hair, over something like lawn furniture?
Pre-brutalizing your populace to killing any sapiens is enough to brutalize them towards harming anyone else. This is the core of the "imperial boomerang", or the colonial boomerang theory, as to why the great wars of the 20th century took on such a nasty character. The ease with which we dehumanized subject populations was - all too easily - redirected against the neighbors, most memorably with Germany trying to re-create the American West to their East.
And yet you are also likely to argue “weather is not climate”. Differences in population characteristics of all kinds have massive societal implications and we should lean into addressing them.
people trying to force everyone else to accept their poorly defended notions of race superiority have a much larger social impact than any quantifiable differences in the genetics of populations.
Evolution is survival of the fittest. That's not a tautology, it actually says something, namely that the traits which survive and thus propagate tend to be the ones that enable some form of adaptation to its living conditions to the individual. The paper lists a bunch of examples:
- lactose tolerance
- immunity and disease resistance
- lighter skin at northern latitudes
- metabolism and vitamin D processing changes in response to changes in diet after the rise of agriculture
All these traits go beyond just increasing the odds of survival, they improve the life of the individual directly. I.e. they confer fitness. Individuals carrying those traits will, on average, in that ecosystem they are inhabiting, be more healthy than those who don't.
It's more reproducing than surviving. If the population of some species increases and the number of copies of some allele remains constant we could consider than gene less fit than the other alleles, in the population genetics sense. So it's frequency rather than survival that geneticists look at. But that proves that there are indeed other ways that they could have defined fitness if they wanted to.
The flip side is everything is being degraded by random mutation.
It's like holding a large ball in place on a hill that sees frequent tremors. If the ball is still halfway up the hill it's being held in place, if it's being held in place it's still halfway up the hill. It might be considered a tautology if you're only working with symbols and ignore all the mechanistics.
Remember, all improvements are changes, but most changes aren't improvements. The trick that makes evolution works is this: out of lots of random changes, most of which are harmful, the harmful ones tend to be weeded out and the useful ones tend to spread.
Whatever does not survive stops registering in later times; most of the time, what helps survival is retained, and what helps survival is what increases fitness.
As stated, this feels wrong. Specifically, it does not account for traits being appropriate for environment. I like to say it as what was needed for one stage could be the problem for the next stage.
That is, traits that stop registering may no longer be something that helps survival. But that does not mean they were not necessary for survival at an earlier point.
How exactly does that contradict the concept of fitness?
Several examples from the paper are exactly that. E.g dark skin was better for survival in Africa, but as populations moved north light skin was strongly selected for. Given the levels of sunlight in Europe, lighter skin increased fitness.
It is against the idea that the beneficial traits will survive to the present. It could be that there was some trait/gene that was absolutely needed for survival in the past, that flat out became irrelevant and dropped off before the present.
That is, it is not an argument against any of the traits that are present. Is why I said the problem is with how it was stated. But you do not have everything with you to provide evidence for all of the things necessary for you to have gotten here. At best, you have evidence that nothing you have with you prevented you from getting here.
That make sense? I grant that pulling it back up, I see the comment I was responding to was hedged. My concern is largely against the idea that things that "were selected for" in the past can be determined by evidence. I'm not convinced it can't be. But I find this presentation of it to be somewhat weak.
But I bet there will be a ton more of that too, thanks to the high quality dataset.
Interesting. I find that part of the paper the most exciting. We always knew selection would happen for valuable traits. But seeing demonstrations of it in the timelines we have is pretty important.
This study covers about 10,000 years of recent human evolution in Europe and West Asia.
From the abstract:
>in the past ten millennia, we find that many hundreds of alleles have been affected by strong directional selection. We also document one-standard-deviation changes on the scale of modern variation in combinations of alleles that today predict complex traits. This includes decreases in predicted body fat and schizophrenia, and increases in measures of cognitive performance. These effects were measured in industrialized societies, and it remains unclear how these relate to phenotypes that were adaptive in the past. We estimate selection coefficients at 9.7 million variants, enabling study of how Darwinian forces couple to allelic effects and shape the genetic architecture of complex traits.
Different evolutionary paths between races/regions, with impact on mental health and cognitive performance.
What you think the implications are of that for your present day lived experience, that might be a different conversation.
> We finally observed signals of selection for combinations of alleles that today are associated with three correlated behavioural traits: scores on intelligence tests (increasing γ = 0.74 ± 0.12), household income (increasing γ = 1.12 ± 0.12) and years of schooling (increasing γ = 0.63 ± 0.13). These signals are all highly polygenic, and we have to drop 449–1,056 loci for the signals to become non-significant (Extended Data Fig. 10). The signals are largely driven by selection before approximately 2,000 years )*, after which γ tends towards zero
Presumably pressure in different regions lead to different combinations of those alleles, which I think they are shorthanding a bit, but the fact that those alleles exist makes blank slate theory a kind of rough assumption
If anything they seem to support homogenization of intellectual capacity/mental health in Eurasia since 2kya.
The methodology, if it holds up, seems to hold a lot of promise for answering questions like this in the future.
> If anything they seem to support homogenization of intellectual capacity/mental health in Eurasia since 2kya.
I would be interested in how you came to that conclusion, unless I'm misleading your post and you specifically mean West Eurasia
> Just because an allele, SNP, or trait swept into or out of West Eurasia during this time doesn’t mean this happened only in West Eurasia. Researchers can use the new computational methods to look for directional selection in other populations worldwide that have enough ancient DNA sequences and construct a clearer picture of what’s unique to different groups and what generalizes across populations.
> Reich expects that future studies will show that shared selective pressures acted on some of the same core traits across diverse human groups, even as those groups split off and migrated to different parts of the world over tens of thousands of years.
https://hms.harvard.edu/news/massive-ancient-dna-study-revea...
Now I would be quite curious to know how they constructed this polygenic score
But that's a strawman. Racism is wrong, even if there are minor genetic variances across populations (which... seems obvious?) Variance within a population strongly dominates the weak cross-population effects, and personal history (nutrition, education, etc) strongly dominates that.
And that's setting aside the moral implications of judging someone or changing your behavior towards them even if you have somehow measured them to be "less intelligent," as if that was a single axis of worth.
Because, apparently, this needs to be said.
That may certainly be true.
(Not OP, but) I always shutter when we want to deny scientific results because it might be "helpful" for someone making a racist argument.
My personal belief is that truth is the goal of science. Even in cases where the truth is uncomfortable.
There is no scientific breakthrough that has occurred sans politics. Politics choose the winners and the losers, and the realm is science is no exception.
All science is political, because the scientific institutions are made up of people, who are political. Your research project lives and dies by politics, as does your dissertation, who gets published, who receives awards, etc.
So when it comes to research of limited utility that has a nasty cadre waiting in the wings to pounce upon it, the wise person would think twice.
So when you tell them to "trust the science" -- be it vaccinations, climate change or something else -- they have no reason to trust that science.
But I think going down this path of denying (or hiding) science that can be used for bad ideas ends up causing (rightly, imho) a distrust of science -- which is far worse.
A distrust of science (not saying it was caused by this particular issue) is how we ended up with so much anti-vax sentiment in the US. And that is the reason we are seeing outbreaks of diseases that used to be minimal.
I think if you want people to "trust the science", you have to trust the people.
My main resistance to that is much the same as yours: the differences are so small, that re-architecting society around them is not going to be enough juice for the squeeze.
But one could also argue that the juice is not even the point: by re-architecting society in this way, you "pre-brutalize" your population so that their threshold for violence against "others" is lowered. Thus your population is closer to being wholly militarized, and theoretically is more effective in war, and is less captured by "weak" or "unmanly" moral ideals, such as empathy.
While this might seem a virtue to someone of an expansionist mindset, in application this principle never, ever works well - again, thanks to those tiny differences. If a citizen is pre-brutalized to have a lowered resistance to killing those with curly hair, how long is it before they kill their next door neighbor with wavy hair, over something like lawn furniture?
Pre-brutalizing your populace to killing any sapiens is enough to brutalize them towards harming anyone else. This is the core of the "imperial boomerang", or the colonial boomerang theory, as to why the great wars of the 20th century took on such a nasty character. The ease with which we dehumanized subject populations was - all too easily - redirected against the neighbors, most memorably with Germany trying to re-create the American West to their East.
If you’re talking about trying to improve the genetics of populations at scale… yikes.
https://en.wikipedia.org/wiki/Fitness_(biology)
It's like holding a large ball in place on a hill that sees frequent tremors. If the ball is still halfway up the hill it's being held in place, if it's being held in place it's still halfway up the hill. It might be considered a tautology if you're only working with symbols and ignore all the mechanistics.
"degraded"? Aren't random mutations precisely one of the core mechanism of adaptation?
Remember, all improvements are changes, but most changes aren't improvements. The trick that makes evolution works is this: out of lots of random changes, most of which are harmful, the harmful ones tend to be weeded out and the useful ones tend to spread.
That is, traits that stop registering may no longer be something that helps survival. But that does not mean they were not necessary for survival at an earlier point.
Several examples from the paper are exactly that. E.g dark skin was better for survival in Africa, but as populations moved north light skin was strongly selected for. Given the levels of sunlight in Europe, lighter skin increased fitness.
That is, it is not an argument against any of the traits that are present. Is why I said the problem is with how it was stated. But you do not have everything with you to provide evidence for all of the things necessary for you to have gotten here. At best, you have evidence that nothing you have with you prevented you from getting here.
That make sense? I grant that pulling it back up, I see the comment I was responding to was hedged. My concern is largely against the idea that things that "were selected for" in the past can be determined by evidence. I'm not convinced it can't be. But I find this presentation of it to be somewhat weak.