Post-Columbian Evolution – Holes

At this point, we have some decent examples of post-Columbian evolution, genetic changes in New World populations after 1492. There is evidence for selection for increased fertility in Quebec, along with increased mutational load due to relaxed selection. Something similar must have occurred in American colonial populations.

I think that the Amish are probably becoming plainer, thru the boiling-off process – which can’t be a common mechanism, because it requires very high fertility, enough to sustain a substantial defection rate.

HbS (sickle-cell) gene frequency has almost certainly decreased significantly among African-Americans – a simple model suggests by about half. There has probably been a decrease in other expensive malaria defenses.

There are a couple of recent papers that touch upon genetic changes that were caused by Old World diseases. Among Mestizos, there’s an excess of European ancestry at 1p36 and 14q32, and an excess of African ancestry at 6p22 (HLA region). Another paper, which looked at contemporary and ancient DNA among an Amerindian population from the northwest coast of North America, found a particular HLA-DQA1 variant went from 100% in pre-Columbian remains to 32% today, a far bigger change that you would see just from admixture. I think we’re talking about smallpox, although not that alone.

In principle, if you had an immune gene that defended against an Old World pathogen that didn’t cross into America, Amerindians would have gradually accumulated nonfunctional variants, just from mutational pressure. the percentage of people with such mutations in any particular immune defense gene would not be very high (not in only 500 generations) but since there are many such genes, the fraction of Amerindians with at least one such hole in their immunological armor might have been significant. Probably this would have been more of a problem in the Caribbean islands, where the Taino seem to have just melted away… Presumably most such holes are gone now in surviving populations, but you might be able to identify them in pre-Columbian DNA.

I see where some Kraut is saying that we now know that human evolution is continuing. I think that’s been an obvious conclusion for almost 160 years.

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the cards fall

People are doing GWAS studies on alleles that influence educational achievement – IQ alleles, more or less – and are finding some. Once you find them, the natural question is how the frequencies of those vary in different populations. Do populations that test low on IQ have fewer plus alleles than those that test high?

This can get complicated, at least if the populations you’re comparing are highly divergent. If they are, the set of education alleles in one pop might be significantly different than the set in the other. Pygmies are like this with height: they share many of the alleles that affect height in Europeans, but also have some of their own. Of course, the most divergent human populations, Pygmies and Bushmen, are few in number and have no significant diasporas.

If all you want to know is the source of population differences, you can easily get around this: look at a mixed population and see how IQ varies with the degree of admixture.

Next question: what would be the implications of various possible results? Suppose that GWAS hits and admixture studies suggest that population ancestry did not matter. Every population is equal in genetic potential for intelligence. That would be a surprise – things sure don’t look that way. It would suggest that a potent and unknown environmental influence(s) was responsible for observed differences. I doubt this outcome a whole lot, but it’s a big universe.

Next possibility: the distribution of IQ alleles predicts what we already see. Those populations that test low have correspondingly low frequencies of plus alleles. Things are the way they look – no real surprises.

Last: things are mostly the way they look, but at least one population does a lot worse (or better) than you would expect from their measured IQ-allele frequencies. I think if you had done this 100 years ago there would have been some anomalies of this sort – populations with serious iodine shortages would have had anomalously low scores. If we hadn’t known about iodine shortages and their consequences, this kind of result would have hinted at it.

Next question: what would the impact of such results be?

For option 1: we would start looking hard for that indumbnifying environmental influence. We would want to be able to turn it off – or on.

Option II and III: Much would be explained. But the results would be almost entirely rejected. How many minds would be changed? Hardly any. You’d have to know a fair amount about genetics to even appreciate the evidence. No matter how sound the result, various bastards will emit a fog of lies about it – not many people would be able to see through that fog, and even fewer would want to. I know of a couple of cases in which people who were disinclined to believe in the results of twin studies came to accept them after GCTA results – extrapolating from that example, results like II or III would change the minds of hundreds of people worldwide.

This doesn’t mean that there would never be any consequences. There would eventually be practical applications of such a result, and the people working those applications would know and understand it.

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“transgender” people aren’t: they’re just crazy. Whittling doesn’t change the wiring of the brain, or the chromosomes. But in principle, such a transformation is possible. It would be an example of real, deep biological change – not the the tinkering at the margins we’re actually on the verge of.

When you think about full metamorphosis in insects, taking a caterpillar into a butterfly, it’s pretty impressive. You wouldn’t guess that a caterpillar and a butterfly were even related – they’re really different. If we hadn’t seen it happen, nobody would believe it possible. Although there are comparable transformations in other species. Sacculina, basically a barnacle, crawls along the body of its host crab until it finds a joint – whereupon it sheds its carapace and injects a microscopic sluglike essence into the crab. It then develops a root system of tendrils , which infiltrate the crab’s nervous system (taking command) and extract nourishment from the crab’s intestine and stomach. The crab is reprogrammed – it looks like and acts like a female crab, but but focuses is efforts into caring for Sacculina’s eggs.

Such natural examples show that really advanced biological engineering is possible, even though we don’t know enough to pull it off yet.

But someday we will. Or any rate we will unless we destroy civilization first, which seems more likely.

Changing sexes (in humans) is not as complicated as turning into a butterfly, but it would seem to require undoing and re-developing a fair amount of brain circuitry. Also changing / redeveloping genitalia, skeleton, muscles, etc. The fact that butterflies can remember some things that they learned as caterpillars suggest this process would be compatible with continuity of identity – so afterwards you would still be ‘you’. Kinda sorta.

Given this kind of capability, changing sex seems fairly trivial. Why not turn into a butterfly? Or considering the square-cube law, a centaur, or a merperson?

Eventually, people would be able to easily transform into a physical form that reflected their true inner nature. I think it’s pretty obvious what that would be for most individuals.

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Such a thing

“there’s no such thing as race” is a standard sentence in the United States and Europe. Conventional wisdom, and like so much conventional wisdom, false.

Of course there is.

First you need to define your terms. I would suggest that any population – a group whose members have mated within that group, almost entirely, for some time – and has experienced strong-enough natural selection to change significantly in some trait that we give a shit about can usefully be considered a race. Or a ‘goklu’, where goklu has exactly the same operational meaning as race, without having yet acquired any toxic associations. Low levels of inward gene flow allow selection to change the frequencies of alleles, so mating within the group is important. Usually this endogamy is a natural consequence of geography (not much gene flow across the Atlantic before Columbus) but sometimes it has been caused by social rules, as in the case of the Ashkenazi Jews or the Hindu castes.

low inward gene flow: in order for significant differences in the neutral genome to accumulate, there must have been < 1 immigrant per generation for tens of of thousands of years or more. That has happened sometimes, and not just with Neanderthals: sub-Saharan Africans and Eurasians were that separate until fairly recently, and have that kind of differences in their neutral genomes. For that matter, Bushmen and Bantu were genetically distinct for an even longer period. So it takes only a little gene flow to stop drift in its tracks.

Selection can be a lot stronger, and it takes more gene flow to scotch it. You could have effective selection for IQ among the Ashkenazi Jews even in the presence of as much as 0.5% inward gene flow per generation from the general European population. 2% would have been too much, though.

A long period of genetic isolation does not automatically generate differences in any particular trait: but it does show that there has been an extended opportunity for selection to operate effectively and generate population differences.

So when we see differences, how old are they? and how can we tell? Plausible selection pressures could generates one-std trait differences in as little as a thousand years, and in some cases, like the Ashkenazim, it likely has. In other cases it may have operated over tens of thousands of years, even as much as quarter of a million years (Bushmen/Pygmies versus other humans).

If the trait in question is characteristic of a geographically extended population, you might suspect that selection had operated over a long time. But since we now know that there have been many population expansions and replacements, you might be wrong. Ancient DNA may be a better guide.

So sometimes the explanation for the differences between two populations may go back deep into the Ice Age, but it might also have happened since the birth of agriculture, or even since the fall of Rome.

Suppose you have a one-std difference in some trait between two populations? What can we say about the genetic architecture? Well, sometime it boils down to the presence or absence of a single allele. Other times it is caused by a shift in the frequencies of a number of alleles that each have a small effect on the trait.

African-Americans average about 1-std lower in white count. That’s all due to the Duffy allele. All else equal, northern Europeans are a couple of centimeters taller than southern Europeans: that is caused by frequency differences in hundreds of alleles affecting height, a shift that on the whole has increased the frequency of plus variants.

So what to say to someone that asks about the ‘race gene’? First, you tell her that she’s an idiot. The complex of shovel-shaped incisors, thick hair, small breasts, more eccrine sweat glands, and a different shape to the hangy-down part of the ear, fixed in northeast Asia, is indeed caused by a single allele, an EDAR variant that is essentially nonexistent in Europe or Africa. On the other hand, Pygmy height, or the lack of it, is influenced by a number of alleles.

But the genetic architecture isn’t all that important: it’s the differences that matter. Pygmies are really short – that’s what matters.

Along those lines, Lewontin and other bullshit artists have tried to argue that genetic statistics are such that human groups can’t really be different. Most genetic variation in humans is within-group, rather than between-group: so fucking what? the same is true for dogs: am I supposed to think that pit bulls and Chihuahuas and border collies are ‘really the same’?

Having more plus variants in the alleles that affect a particular quantitative trait doesn’t show up in these genetic statistics (like Fst) at all. Neither would a big frequency difference in a single allele that had a big effect, like EDAR.

People are mostly about as different as they seem to be. There are exceptions, cases where an environmental insult makes a fair amount of difference. This is particularly the case with height, where nutritional status can easily create a 1-std difference. But height is influenced by genetics, too, and the shortest people (the Pygmies) are short for genetic reasons, not because they’re starving.

What about the magic immunity of the brain to natural selection? That’s nonsense, of course. We know, for sure, that different goklus have different distributions of personality traits – because they act significantly differently with 24 hours of birth. All the psychometric results indicate that goklus vary in intelligence too [perhaps 3 stds from highest to lowest] probably largely because of differences in the frequency of many alleles with small effects.

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If you had a reasonably cheap particle accelerator, one that could produce a high flux of few-GeV neutrinos, you could make yourself some real money.

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Bugs Versus Drift

For a while now we have seen occasional articles about how people outside of sub-Saharan Africa may have more genetic load, generated by drift over a population history in which Eurasians generally had a smaller effective population size. This is related to those recent papers with similar but stronger conclusions about Eurasian archaic humans like Neanderthals and Denisovans.

As I mentioned, I kind of doubt that that Neanderthals and Denisovans were all that screwed up – partly because a more complete theory indicates that salvage mutations get easier as you drift away from the optimum and ameliorate the effects of low population size to a surprising degree, but even more because the Neanderthals obviously weren’t all that screwed up, didn’t have their fitness depressed by tens of percent, because they stood off anatomically modern humans for something like 70,000 years after first encounter. Results count. The mechanism makes a lot more sense for Flores hobbits because their population was much smaller, but even more because they actually were screwed up: it shows in their skeletons.

So, just how screwed up do Eurasians look, compared to Africans? I mean, if we’re going to be busy explaining a phenomenon, shouldn’t we bother to make a cursory check to see whether it even exists? I know that probably sounds radical…

Of course there’s no bloody sign of any such thing. Sub-Saharan Africans have shorter lifespans and lower IQs than most Eurasian populations. East Asia has lower genetic diversity than Europeans – so has had lower effective population size over the past few tens of thousands of years – yet those populations have higher average IQs and longer lifespans than Europeans.

On the other hand, it is also the case that strong selection for any particular trait tends to mess up other traits – logical, considering trade-offs. So strong selection for resistance to falciparum malaria has made lots of deleterious variants common in the tropical and subtropical parts of the Old World. We know many that are strongly, obviously bad for you – even lethal – but there are surely many others with milder (but still negative) effects. We know that selection for resistance to sleeping sickness has selected for APOL1 variants that greatly increase the risk of kidney failure, so that African-Americans develop end-stage renal disease (ESRD) about 3.5 times more often than people of European ancestry. Those APOL1 variants also exacerbate kidney disease caused by sickle cell, and there’s an AIDs-related kidney-wrecking syndrome (HIVAN: HIV-associated collapsing glomerulopathy) (while AIDs is of course much more common in blacks) that seems to require those African APOL1 variants – HIVAN is up to 50 times more common in blacks than whites. Those social constructs can sure seem real when they’re shoveling the dirt over your face.

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The 1%

We don’t see people today with Neanderthal Y chromosomes or mtDNA. I keep hearing people argue that this means that mating between Neanderthal males and AMH females must have produced sterile males, or that matings between AMH men and Neanderthal women were all sterile, or whatever.

That is not necessarily the case. A slight disadvantage is all that would be required to totally eliminate Neanderthal Y-chromosomes or mtDNA.

Imagine that a Neanderthal Y-chromosome reduces the bearer’s fitness by 1%, and that the original frequency of Neanderthal Y chromosomes (after admixture) was 2%.

It’s been something like 1500 generations. The expected frequency is 5.67 x 10-9. In real life it would probably have fluctuated to zero, and of course stayed there.

Understand and remember.

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