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Amish Mutation Protects Against Diabetes and May Extend Life - The New York Times
What Dr. Vaughan and his colleagues discovered was striking. Amish carriers of the mutation live on average to age 85, about 10 years longer than their peers. Among the Amish who did not have the mutation, the rate of Type 2 diabetes was 7 percent. But for carriers of the mutation, the rate was zero, despite leading the same lifestyle and consuming similar diets. Tests showed that carriers of the mutation had 28 percent lower levels of insulin, a hormone whose chronic elevation can lead to Type 2 diabetes.
news  org:rec  genetics  genomics  pop-diff  recent-selection  usa  midwest  longevity  health  hetero-advantage  cardio  metabolic 
november 2017 by nhaliday
What Does a “Normal” Human Genome Look Like? | Science
So, what have our first glimpses of variation in the genomes of generally healthy people taught us? First, balancing selection, the evolutionary process that favors genetic diversification rather than the fixation of a single “best” variant, appears to play a minor role outside the immune system. Local adaptation, which accounts for variation in traits such as pigmentation, dietary specialization, and susceptibility to particular pathogens is also a second-tier player. What is on the top tier? Increasingly, the answer appears to be mutations that are “deleterious” by biochemical or standard evolutionary criteria. These mutations, as has long been appreciated, overwhelmingly make up the most abundant form of nonneutral variation in all genomes. A model for human genetic individuality is emerging in which there actually is a “wild-type” human genome—one in which most genes exist in an evolutionarily optimized form. There just are no “wild-type” humans: We each fall short of this Platonic ideal in our own distinctive ways.
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november 2017 by nhaliday
Post-Columbian Evolution – Holes | West Hunter
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.


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.
Sarazzin acknowledges it.

interesting guy:
He became well-known worldwide after publishing a controversial book about Muslim immigrants in Germany in 2010.[3] In his book Deutschland schafft sich ab ("Germany abolishes itself"),[4] he denounces the failure of Germany's post-war immigration policy, sparking a nationwide controversy about the costs and benefits of multiculturalism.
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october 2017 by nhaliday
Second Bananas | West Hunter
Still thinking about domestication. Mostly,  the wild ancestors of domesticate animals were social: presumably, such behavioral tendencies were preadaptations that helped the domesticates come to bond with or at least tolerate people.   Social animals can have adaptive personality variation – difference behavioral strategies.  Sometimes those strategies are facultative, sometimes genetic, sometimes a mix.

I would guess that those wild individuals that account for most of the ancestry of f a domesticated species didn’t have a representative mix of personality types. Probably they were more likely to be followers rather than leaders – not the alphas of the pack, not the most aggressive stallions.  Sidekicks.  With dogs, we can probably check this hypothesis fairly easily, since wolves are still around.
A few years ago, I was thinking about genetic male morphs. Turns out that you find qualitatively different forms of males in many species: Barry Sinervos’s lizards, Shuster’s isopods, Lank’s ruffs, jack salmon, etc. Logically, the Y chromosome would be the best place for a such a genetic switch, since that would avoid negative side effects in females. The problem is that the Y carries very few genes.

Alternate strategies don’t have to to be as complicated as they are in ruffs or Uta stansburiana. Different levels of aggressiveness, or different points on the cad/dad axis, would have different selective payoffs in different environments. If a new environment favored lower (or higher) aggressiveness in males , a Y-chromosome that induced lower (or higher) aggressiveness would take off. And since different Y chromosomes do indeed affect the level of aggressiveness in mice [which I just found out], possibly by affecting testosterone production – this mechanism is plausible.

This could explain a funny genetic pattern in the domestication of horses. There’s a fair amount of diversity in horse mtDNA: it looks as if many different mares were domesticated. On the other hand, it looks as if only one stallion was ever domesticated. All living stallions today are his descendants.

Stallions are pretty aggressive, and must have been hard to tame. Maybe one was genetically unusual – wimpier. Tameable.

Fortunately for all concerned, the selective value of aggressiveness, etc. has been the same for all human populations forever and ever, before and after the development of agriculture. Otherwise you might see weirdly rapid expansions of particular Y-chromosome haplogroups – common, yet only a few thousand years old.
A while ago, I wondered if modern stallions are a male morph adapted to domestication, one in which the strategy is mediated via the Y chromosome.

Looks as if I was right*. Check out “Decline of genetic diversity in ancient domestic stallions in Europe”.

Selection favored one particular kind of Y-chromosome. This had to be based on phenotype, not genealogy. Most likely it was favored under the new environment of domestication. Somehow, these stallions performed better, or were easier to get along with (my bet).

We already knew that Y-chromosomes could do things: Haplogroup I increases the risk of heart disease by about 50%, while the particular variant of Y chromosome influences aggression in mice.

Which means you have to re-examine the starburst phylogeny of R1b and R1a: it’s probably biology, rather than history, that drove those expansions. Some kind of selective advantage. Possibly one reason that those particular Y chromosomes far outraced steppe autosomal contributions. Most likely, R1a and R1b induce specific morphs – their carriers are somehow different. Maybe they’re born to be mild, or born to be princes of the universe. Maybe an R1b guy just finds it easier to cooperate with other R1b guys… Or maybe they’re resistant to typhoid.

* correct predictions mean nothing in biology. Ask any biologist.
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september 2017 by nhaliday
House O’Rats | West Hunter
Not content with our simple selection experiment, we also install complicated mazes with flaming hoops that the rats have to jump through in order to get extra food and mates: we want rats with different brains, and eventually we get them. They’re maze-bright and flaming-hoop-bright. We install treadmills and feed the rats according to their work output, and eventually they produce more work per amount of food eaten. They’ve maximized efficiency rather than surge power, which was more useful back when they were wild and free. Not only that, they eventually come to like being on the treadmill, almost as if it’s some sort of race.

There are other silos – one full of rice and another full of maize. They have different mazes and flaming hoops, built at different times: and there are still wild rats, too, although not as many as in the silos.

But no matter how much they change, they’re still just a bunch of rats.
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september 2017 by nhaliday
It made their brown eyes blue.. | West Hunter
Assuming population continuity, the selective advantage of the alleles they examined must have been very high. In order to see if there had been population continuity, they looked at the mtDNA frequencies of the ancient populations and compared them with mtDNA frequencies of modern populations in the same areas. Since they’re different, but not wildly different, they conclude that there has been population continuity, which was their null assumption.

That null assumption might have been reasonable, if someone had burned every history book ever written, while at the same time suppressing all the ancient DNA evidence.

Since that has not yet happened, I think their assumption is downright embarrassing. People have been moving in and out of this area for all of recorded history (as Razib Khan has also pointed out) : Cimmerians, Scythians, Goths, Khazars, Kievian Rus, the Golden Horde, eventually Russians.

There is no logical reason for geneticists to ignore information outside their field. Ignorance is no excuse. I could say the same for every other discipline. Cross the streams – it would be good.
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august 2017 by nhaliday
Krazy Kats | West Hunter
The way things are going, the cats with the greatest reproductive success will be feral, and the cats best adapted to living with people will have low fitness. Razib Khan has talked about this.  There are a number of other cases in which humans are inadvertently selecting for outcomes they don’t like: deer are getting smaller antlers, we’re seeing more and more jack salmon, etc.  And of course we’re selecting ourselves for this and that, none of it good.

Yet Carlos Driscoll, a University of Oxford biologist, says there’s nothing to worry about re cats. “The population of domestic cats has been stable for a very long time,” Driscoll said.
“There’s a lot of genetic inertia there.”

The thing is, there’s no such thing as genetic inertia.   You can change any species with selection. Horseshoe crabs have been around for something like 450 million years – they’re older than most mountain ranges –  but if you started selecting them for size, or a different reproductive schedule, or the ability to live in brackish water, or the ability to play Go  – change would come.
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august 2017 by nhaliday
Polygenic Adaptation has Impacted Multiple Anthropometric Traits | bioRxiv
By comparing these polygenic scores to a null distribution under genetic drift, we identify strong signals of selection for a suite of anthropometric traits including height, infant head circumference (IHC), hip circumference (HIP) and waist-to-hip ratio (WHR), as well as type 2 diabetes (T2D). In addition to the known north-south gradient of polygenic height scores within Europe, we find that natural selection has contributed to a gradient of decreasing polygenic height scores from West to East across Eurasia, and that this gradient is consistent with selection on height in ancient populations who have contributed ancestry broadly across Eurasia. We find that the signal of selection on HIP can largely be explained as a correlated response to selection on height. However, our signals in IHC and WC/WHR cannot, suggesting a response to selection along multiple axes of body shape variation. Our observation that IHC, WC, and WHR polygenic scores follow a strong latitudinal cline in Western Eurasia support the role of natural selection in establishing Bergmann's Rule in humans, and are consistent with thermoregulatory adaptation in response to latitudinal temperature variation.
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july 2017 by nhaliday
Dogs and Men | West Hunter
Razib Khan talks about a new article that suggests that dogs were domesticated quite a long time ago, perhaps more than 35,000 years ago, well before the last glacial maximum.

We know that dogs have adapted to life with people, have changed in many ways.

I wonder how humans adapted to dogs.  If they were like modern pariah dogs, hanging around the village and eating garbage, doesn’t seem that they would have been that influential. But if used in hunting, they could have been very important, especially back in the Ice Age – and if they were that important, the partnership might have generated significant selective pressures in humans.
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june 2017 by nhaliday
None So Blind | West Hunter
There have been several articles in the literature claiming that the gene frequency of the 35delG allele of connexin-26, the most common allele causing deafness in Europeans, has doubled in the past 200 years, as a result of relaxed selection and assortative mating over that period.

That’s fucking ridiculous. I see people referencing this in journal articles and books. It’s mentioned in OMIM. But it’s pure nonsense.
The only way you’re going to see such a high frequency of an effectively lethal recessive in a continental population is if it conferred a reproductive advantage in heterozygotes. The required advantage must have been as large as its gene frequency, something around 1-2%.

So it’s like sickle-cell.

Now, if you decreased the bad reproductive consequences of deafness, what would you expect to happen? Gradual increase, at around 1 or 2% a generation, if the carrier advantage held – but it probably didn’t. It was probably a defense against some infectious disease, and those have become much less important. If there was no longer any carrier advantage, the frequency wouldn’t change at all.

In order to double in 200 years, you would need a carrier advantage > 9%.

Assortative mating,deaf people marrying other deaf people, would not make much difference. Even if deaf people substantially out-reproduced normals, which they don’t, only ~1-2% of the copies of 35delG reside in deaf people.
west-hunter  scitariat  rant  critique  thinking  realness  being-right  clarity  evolution  genetics  population-genetics  recent-selection  null-result  sapiens  tradeoffs  disease  parasites-microbiome  embodied  multi  poast  ideas 
may 2017 by nhaliday
Syphilis in Renaissance Europe: rapid evolution of an introduced sexually transmitted disease?
When syphilis first appeared in Europe in 1495, it was an acute and extremely unpleasant disease. After only a few years it was less severe than it once was, and it changed over the next 50 years into a milder, chronic disease. The severe early symptoms may have been the result of the disease being introduced into a new host population without any resistance mechanisms, but the change in virulence is most likely to have happened because of selection favouring milder strains of the pathogen.
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may 2017 by nhaliday
Soft sweeps are the dominant mode of adaptation in the human genome | bioRxiv
Detection of 2000 instances of recent human selection, half of which are specific to individual human populations, and many of which affect the central nervous system. Note this doesn’t cover polygenic selection, so it’s a very loose lower bound on how much recent human evolution there has been.

How Sweeps Get Soft:
A puzzling finding from the search for selection in humans is the large number of apparently selected variants versus the apparent absence of high frequency selected regions and regions that have become fixed in our species.

Cochran, John Hawks, and I were involved in some of this work, and we all thought immediately without any discussion that the intermediate frequency sweeps must reflect heterozygote advantage.
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may 2017 by nhaliday

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