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Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

reich.hms.harvard.edu

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Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#41

Post by timmg »

kstenerud wrote: post #39
timmg wrote: post #34

Earlier quoted context omitted.

> 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 t…

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 projec…

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#42

Post by MarkusQ »

astrobe_ wrote: post #40
fluidcruft wrote: post #25

Earlier quoted context omitted.

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.

> The flip side is everything is being degraded by random mutation "degraded"? Aren't random mutations precisely one of the core mechanism of adaptation?

But most of them are still deleterious.

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#43

Post by SubmarineClub »

taeric wrote: post #28
nine_k wrote: post #24

Earlier quoted context omitted.

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#44

Post by taeric »

SubmarineClub wrote: post #43
taeric wrote: post #28

Earlier quoted context omitted.

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#46

Post by asdff »

timmg wrote: post #16
vintermann wrote: post #5

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.

Makes you wonder what is being selected for currently.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#47

Post by MarkusQ »

taeric wrote: post #44
SubmarineClub wrote: post #43

Earlier quoted context omitted.

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 provid…

More to the point, TFA is specifically addressing the issue (which is part of what makes it a big deal).

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#48

Post by taeric »

MarkusQ wrote: post #47
taeric wrote: post #44

Earlier quoted context omitted.

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 provid…

More to the point, TFA is specifically addressing the issue (which is part of what makes it a big deal). 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 se…

Apologies, I only meant my gripe with the comment I was responding to. Is why I put "as stated." I meant that to be that I was not arguing what I think they were messaging towards.

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#49

Post by asdff »

kloop wrote: post #11
Tor3 wrote: post #6

Earlier quoted context omitted.

Just where did you get that from? Certainly not from the paper.

I think they're talking about this bit: > 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…

It is important to consider that these alleles are merely correlated to behavior and are not proved to be causal of any behavior. For example, maybe you sample bankers in NYC. You can probably assume you'd get a lot of perhaps semitic genetic background in this dataset. Now, would you conclude that Jewish people have some inherent gene that makes them want to be bankers like a moth to a lamp? Maybe you would. But more likely situation is that people tend to follow the profession of people in their lives who work that profession and can inform them about it, and for centuries there were real legal restrictions in a lot of places preventing anyone but jews from being allowed to charge interest. So, pretty good odds today as a jew you know someone who works in finance and can help at least to some degree point you towards that field.

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.

Re: Ancient DNA reveals pervasive directional selection across West Eurasia [pdf]

#50

Post by Nicook »

timmg wrote: post #41
kstenerud wrote: post #39

Earlier quoted context omitted.

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 projec…

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.

I enjoy that you are framing this as somethings that "may" happen in the future.
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