Ancient DNA reveals pervasive directional selection across West Eurasia [pdf](reich.hms.harvard.edu) |
Ancient DNA reveals pervasive directional selection across West Eurasia [pdf](reich.hms.harvard.edu) |
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.
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 political agreement on whether having or not having affirmative action programs is racist (or against which racial groups).
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.
Contra claims elsewhere on this thread, science on this topic isn't suppressed at all. There are multiple branches (in quantitative psychology and genetics) that study this issue actively, and if you follow it, new papers aren't rare. But directionally those papers aren't confirming the priors of the people claiming the science is suppressed, so they don't get acknowledged.
> 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
Now I would be quite curious to know how they constructed this polygenic score
Affirmative action might be problematic for totally unrelated reasons. Maybe there's no way to do it without being racist towards Asians, or without selecting a tiny privileged cohort of Black families to accrue benefits on (simply "applying for college" in the first place situates most people in a position of privilege).
We absolutely do not know enough about the psychometric science here --- forget race entirely and just try to pick through theories of intelligence and its mutability --- to make public policy decisions. It is, at present, a pure scientific concern.
If you’re talking about trying to improve the genetics of populations at scale… yikes.
Then to address the elephant in the room - which is the race discourse subtext let’s be honest - it’s highly unlikely that any recent selective pressure on a separated population, which resulted in meaningful phenotype adaptations, happened similarly everywhere at the same time
So really when you say select for household income among western populations, it might be hard to actually find any real signal that is actually causal that isn't due to simple demographic and historical reasons, due to the lack of power you have in sampling rare demographics within a given category such as high income.
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...
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.
If those leaders believe in the integrity of the scientific institutions, their flock will follow. If they're anti-vax, their flock will follow. If they believe in some medical quackery, their flock will follow. If they believe in eugenics, their flock will follow. It's happened before.
What was fringe yesterday can become mainstream today, with the right leaders.
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.
no, wait, I get it.
all scientists should expect mistrust because of perceptions of bias of any of them, regardless of how well founded. that seems at the very least unproductive.
- 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
Wrong. Fitness is not "beyond" increasing the odds of survival, fitness is ONLY that. Fitness is not about quality of life.
- in that ecosystem they are inhabiting, be more healthy than those who don't.
Survival of the fittest says nothing about how healthy they are, only whether they survive and reproduce or not.
So it should really be "If it survives it must have been fit"
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.
Apologies if I did a bad job explaining my opinion. But I was attempting to argue the exact opposite of that.
My view is that science should be the search for truth. And that if the truth is inconvenient for some political (or other) reason, so bet it. The truth is the goal. Full stop.
My feeling is that if scientists stop pursuing truth in cases where it doesn't fit their politics, they will (rightly, IMHO) lose the trust of the public. (Of course, in particular, those in the public who have different politics.)
Just saying, "We should do science for science's sake" is not enough. We've done that. Go read The Bell Curve and knock yourself out. What people like you seem to want is continued, motivated hammering of the issue.
but you still won't be satisfied with the answer, because even if one set of genes gets you 5% more 'intelligence' score, that still doesn't justify a apartheid state. do you think we should have different rules for people with different IQ scores?
you're saying that because science as a whole isnt particularly interested in assuming _your_ biases, that the whole enterprise is meaningless and corrupt, and thus we can't trust anything those white coats say.
Well that's a given mate, nobody's talking about populations that dont reproduce are they? And even then you're still making the same tautological mistake.... If they survived they must have been fit
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.
They aren't saying "we see these things now, so they must be good" but rather things like "we see these selected for from 9kya to 3kya, but from then to the present they were selected against"; they are specifically looking at how apparent selective pressures changed over time.
> the idea that things that "were selected for" in the past can be determined by evidence
When the evidence is a copious selection of ancient genomes, distributed over both space and time, they certainly can be.
The callout on "evidence" I have there is that I meant that to only be present evidence. And again, I am not convinced it can't be done. It takes a lot of work. Which, the article is doing. But just saying that traits that helped you survive are typically retained, so by definition increase fitness, does not.