Every now and then someone tries to give some genetic argument showing that population A and population B can’t possibly be significantly different in any trait that hurts someone’s feelings. They’re all bullshit.
The most famous one is probably Lewontin’s Fst argument. He said that since most (> 85%) genetic variation in humans is within-group, rather than between groups, human populations can’t be very different. Except for traits influenced by a few genes, like skin color, or a single gene that affects many traits, like EDAR, or a highly polygenic trait influenced by many genes, like height. That is, any kind of trait, with any kind of genetic architecture.
A related argument says that you only see differences in ‘superficial’ traits, like bone density, brain volume, or the shape of the skull. That’s sarcasm.
Another says that populations just haven’t been separated long enough to diverge much. Untrue: selection can move pretty rapidly. Amerindians have undergone noticeable genetic change (mostly immunological) over the past five hundred years. While some human populations been separated for much longer than that: often tens of thousands of years, sometimes (with Bushmen for example) hundreds of thousands of years. Plenty of time.
Lately I’ve seen a few people arguing that there can’t be big between-population differences in highly polygenic traits, those influenced by many alleles of small effect, because evolution of a highly polygenic trait is for some unknown reason very slow -” at least 100 millennia to evolve appreciably”. But that isn’t the case.
They’re thinking about intelligence – but height is also polygenic. Yet Pygmies and Tutsi exist. For that matter, natural selection over the past few thousand years has made southern Europeans shorter and northern Europeans taller.
I have no idea where this notion originated, because there’s nothing in genetic theory or practice that supports the idea that polygenic traits can’t change rapidly. Think of the Maltese elephants, isolated when sea level rose at the end of the ice ages: 3 feet tall in just a couple of thousand years.
While there are many counterexamples in agricultural genetics: you can breed for almost any trait* – appearance, conformation, size, disease resistance, flavor, behavior – and we have done so. Many of those traits are highly polygenic. In fact, Fisher’s infinitesimal model, fairly standard in evolutionary genetics, assumes that an infinite number of alleles influence a trait.
Most of these fallacies are addressed in the tome I’m perusing. The author correctly dismissed all of them. But then…
* except sex ratio. That’s nearly impossible.
West Hunter 
Basic question, but why can’t we breed for this? We sometimes see uneven sex ratios in nature: female alligators outnumber males by 5 to 1.
Maybe not: http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.2000.tb00821.x/abstract
The rarer males are, the more offspring each male has, and thus there is automatically selection for variants that increase the probability of a male offspring. Equilibrium is at 50-50. Fisher figured this out, using game theory, before there was game theory.
And yet there are small but significant and persistent racial differences in human sex ratios at birth, e.g., http://www.bioline.org.br/pdf?rh08043. I first noticed this during my graduate studies in demography, back in the 1970s, but wisely chose to ignore the issue after several fellow students argued that I should just shut up.
I read about it somewhere, but I do not keep records and references thanks to my infinite laziness.
Anyway, they claimed even greater differences in favour of women in some tribes inside matrilineal belt and they attributed the difference to local sexual strategies (lack of stable relationships, uncertainty in paternity, etc.).
Couldn’t you select for a female-biased sex ratio at the family level? Only allow those from families which are 75% female to breed. The males would breed more, but any who passed down a male-biased sex ratio to his offspring would not have success.
You’re assuming what needs to be shown, namely that the sex ratio is genetically based, rather than a product of chance.
If it could be done, animal breeders would probably have done it by now.
There are exceptions to the rule, and they are mostly theoretically understood I believe. Gig wasps tend to be famously female skewed for subtle reasons related to between-family selection unique to fig wasp reproductive behavior. I think Hamilton was the first to figure that out in a paper called Extraordinary Sex Ratios.
Fig wasps
I liked “Gig wasps”.
i like the idea of gigawasp as a unit of measurement
Actually, we could probably take a hint from fig wasp reproductive behavior to breed female-skewed sex ratios into animals, at least in theory. How? Force all breeding to occur within siblings groups. Sibling groups that then produce more offspring will be better represented in future generations, and a good way for a group to produce more offspring is to have more females. Within-group selection will still favor 50-50, but the induced strong between-group selection will favor more females. The result should be a female bias.
That is, unless close inbreeding totally fucks them all up first.
Meiosis ensures male gametes are a 50/50 ratio of x chromosome to y chromosome.
Thus, there aren’t genes to select for, it’s just chance.
Wrong.
What am I missing Greg?
There are ways to bias meiosis, and there are factors that could favor higher female or male fetal survival. And some species, with unusual ecological niches, really do have wildly unbalanced sex ratios. But the general reason for 50:50 is game-theory balance, like I said.
The anticipation is killing me!
Well, assume that author I’m thinking about hasn’t been fired. That’s a good running start.
Maybe elephants used to swim more than we think. It would explain the snorkel.
There’s some evidence for a semi-aquatic ancestor.
And elephant pelvises, if you look at them, are positioned like a sealion when its on land. I have to wonder just how aquatic their ancestors once were, and how difficult recolonising the land must have been for the tethytheres.
The explanation of the elephant’s trunk is the same as the explanation of the giraffe’s neck: long, LONG legs. They need to drink water and eat, which is nearly impossible with an intake fixed high above the ground.
Other large animals, such as Indricotherium, got by without a trunk.
OT: somebody’s book
https://book.douban.com/subject/27168686/
If I can just get every single person in China to buy a copy…
The most famous one is probably Lewontin’s Fst argument.
Which has been improved on by some anti-racists, as these extracts from the Guardian reveal:
The unwelcome revival of ‘race science’
Its defenders claim to be standing up for uncomfortable truths, but race science is still as bogus as ever.
[…] Race, like intelligence, is a notoriously slippery concept. Individuals often share more genes with members of other races than with members of their own race.
https://www.theguardian.com/news/2018/mar/02/the-unwelcome-revival-of-race-science
The myth of ‘race’ was invented by racism, and racism keeps it growing
Racism is incredibly successful, despite having no basis at all in fact. There is only one race – the human race
[…] The former England [soccer] player John Barnes put it very well in the Times this week: “Race is not a scientific reality. You could find a tribe in Africa who are genetically closer to Europeans than to an African tribe a hundred miles away. Some Saudis have whiter skin than Italians.”
https://www.theguardian.com/commentisfree/2012/feb/17/race-is-a-myth-deborah-orr
The article is unusually dumb, even for the Guardian.
You take that back! That article is almost exactly the median of Guardian dumbness. It is, however, slightly more annoying than the median Guardian article
Well, I don’t often read it, admittedly. How dumb do they get?
someone must now rank-order Guardian articles by dumbness quotient. I would contribute to a crowd fund for this.
This from Polly Toynbeeis more typical.
She is one of the most influential journalists in the country.
I count more falsehoods there than sentences.
I can think of just one interpretation of these words that is technically correct, and it doesn’t actually support the journalist’s worldview if you think about it for a minute.
She is also a member of the heriditary ruling clique in Britain. So either totally lacking in self-awareness or simply a dissimulator.
Maybe she doesn’t actually know much about anything. That’s a common affliction.
public universalist morality -> sociopaths adopting virtue signalling as camouflage
Hereditary genius.
Her grandfather, the historian, from his Wikipedia page: “While on a visit in Berlin in 1936 to address the Nazi Law Society, Toynbee was invited to have a private interview with Adolf Hitler, at Hitler’s request. Hitler emphasized his limited expansionist aim of building a greater German nation, and his desire for British understanding and cooperation. Toynbee believed that Hitler was sincere and endorsed Hitler’s message in a confidential memorandum for the British prime minister and foreign secretary.
Toynbee was troubled by the Russian Revolution, for he saw Russia as a non-Western society and the revolution as a threat to Western society. However, in 1952 he argued that the Soviet Union had been a victim of Western aggression.”
”You could find a tribe in Africa who are genetically closer to Europeans than to an African tribe a hundred miles away.” -As far as I know, that’s a lie: When you compare a single locus it may be true, but when you compare many loci the relationship disappears, so the former soccer player is lying.
Or is just pig-ignorant.
Willful ignorance is the same as lying in my book, and that of many sages. Almost all ignorance in this matter is willful.
Even if true, it wouldn’t imply what they’d like us to believe.
Look at a mountain. There are a lot of spots on it that are further apart from each other than they are from the peak. That doesn’t change the fact that the peak is still the highest place around.
It is true: even if for some strange reason the more somatically remote peoples were more similar genetically to each other than to their immediate neighbors, the morphological and phenotypic differences that we can observe would still exist; with which we could still infer the existence of different races.
You definitely could. That tribe is called ‘White South Africans.’
I’m not really sure that “the soccer player” was referring to the Afrikaners when he was talking about an African tribe in his statement, are you?
I get it.. late ;P
Afrikaners
In that case, he would be contradicting himself: then race is a scientific reality.
Depends on how close together East Africans (lots of early Levant Neolithic and later Arab ancestry, almost 50% in some cases, so relatively close to West Eurasians) live next to groups like Biaka or Hadza who are very divergent from other Africans…
But while technically possible it doesn’t really honestly capture diversity in Africa; much genetic diversity, fairly little structure is the rule of the day there. You could find that the quoted thing is the case, but most groups are Bantu from a recent agricultural expansion who are frankly not very divergent from each other (certainly relative to the land area they cover).
I think Bushmen might be more distant from Bantu than we are, but they split off from one another 200,000-300,000 years ago and we split off 40,000 years ago. So, isn’t that what we’d expect, really?
Anyone with an undergrad level knowledge of cladistics looks at Africa, shrugs, and says “paraphyletic taxon.” There is no population which gave rise to all Africans but not to all other humans. The same can’t be said of all Eurasians, who mostly descend from a group that left Africa ~ 40,000 years ago.
What these disingenuous shitstains like to point out is essentially that there’s no such thing as “the African race,” to the exclusion of non-Africans (true), with the (false) implication that it removes all possibility for diversity somehow. To give you an idea how insane this is:
“The genetic differences between sperm whales and dolphins are greater than between sperm whales and baleen whales, so there’s no such thing as toothed whales to the exclusion of baleen whales. Thus, all whale species are the same.”
I used to shrug ‘paraphyletic taxon’ too, but then, cladistics assumes only divergence, whereas human population are more like nets than trees.
Because they keep interbreeding? I remember something about Bantu having some Bushmen admixture. Some of the links I had bookmarked on this subject have actually died.
Re Bantu mixture with San people?
Here’s one I saved that was published in 2013:
“Our analyses indicate that the best explanation for our findings is that the Bantu-speaking immigrants married resident Khoisan women when they first came to southern Africa, thus incorporating these divergent lineages into their maternal genepool.”
Read more at: https://phys.org/news/2013-01-genetic-admixture-southern-africa-ancient.html#jCp
Awesome, thanks. I don’t remember whether the study I read used autosomal or mtDNA but it painted about the same picture.
“so the former soccer player is lying”
he probably believes it to be true cos he’s been lied to by whoever pulled his strings.
When it comes to genetic science, you can’t beat the expertise of hack journalists and soccer players….
“This claim has long been the smiling face of race science; if it is true that Jews are naturally more intelligent, then it’s only logical to say that others are naturally less so.”
Dang, nothing gets past this guy.
Lewontin actually stole his argument from an earlier race denier. Someone said exactly the same thing about skull sizes. Greater range within groups than between them, therefore group differences in skull size are not significant.
Lewontin was a Leninist, so you can be sure he underlined it and dogeared the page.
Lewontin’s argument does not look convincing if we look at actual traits rather than individual genes. Height and intelligence can be few standard deviations apart.
So in the case he improved much rather than ‘stole’
Remind them that talking about ‘one race – the human race’ is still biological essentialism, and it still uses the word race, thereby prompting oppressive narratives.
There’s a whiff of teleology to the biology deniers. I can’t help but notice that their approach is similar to the Intelligent Design people. The focus is not on producing a plausible theory, but on undermining challenges to their beliefs.
It’s only Fifty- Fifty that I’m getting the phrasing right here — Is it that because in sexual species each new organism comes from one male and one female, game theory predicts that in the long run ratios will tend toward 50:50 in terms of parental investment? ~All~ parental investment, including germ cell production and nurturance? (Think of it as the genes in the parents placing bets on which is optimal for the next generation’s reproductive success, and the game theory shows it’s a fair coin fifty-fifty bet as to which will generate more grandchildren.) As for alligators and other temperature-determining-sex species, one of the reason why obligate-sex-determining species (like us) have generally been more successful is that the fluctuation to try to better fit temporary momentary environmental conditions, ever since the ice ages outside of the equatorial belt, is prone to wild population-level swings in sex ratios and so population crashes. (With the condition of warmness on eggs ~generally~ indicating plentiful food, so normally risk a high variance reproducing male offspring, versus if cold go with a low-variance in sexual reproductive success female offspring.)
Suppose there were more males than females in a population. Giving birth to males is then a higher payoff strategy, because each male can mate with multiple females. Therefore, any genetic variant that increases the chance of male offspring would increase in frequency.
Suppose there were more females than males. Each female can pair up with a male, but not every male can pair up with a female. Therefore, giving birth to more females is the better strategy, and any variant that causes this will rise in frequency.
In this way, the sex ratio is equalized.
Sex ratios can change if the men decide to kill each other in high enough percentages. http://www.science20.com/david_spiegelhalter/why_are_more_boys_born_at_the_end_of_wars-154948. The graph tells it al. Here’s the weird deal. Spikes after World War 1 and World War 2 made sense from this theory but why does the graph shows a spike in 1973 as well. The article goes on to speculate that intense sex causes more boys. Huh? Especially bloody wars and sexual revolutions increase the percentage of boys being born. The war thing makes evolutionary sense. If men are killing each other in high enough numbers than I can see an evolutionary advantage to more boys being born, the intense sex thing causing more boys might be true but color me skeptical.
I don’t buy the explanation. I don’t think that theory works here.
Suppose we have a population with 50-50 ratios at birth, but male mortality is higher pre-adulthood in the species, such that adult ratios are highly skewed. Say, 2 females per male – i.e. 2x higher pre-adult mortality for males. Then it is true that the average fitness of adult males is twice as high for males than for females, because every offspring has one father and one mother.
(Adult Male fitness = #_offspring/#_adult_males,
Adult Female fitness = #_offspring/#_adult_females,
The numerator is the same, so the only thing that matters is adult sex ratio. Half as many males = 2x adult male fitness.)
So selection should favor production of more males, right? Wrong! The problem is you don’t get to create adult males! You can only create infant males, and infant males are twice as likely to die before adulthood! When you multiply the 1/2 times the adult male fitness, you get that the male and female fitness at birth is about the same. So there is no advantage to skewing infant ratios toward males – which is what we’re talking about.
This is presumably why most species out there still have about 50-50 ratios at birth, despite the fact that many species to have higher male mortality and therefore skewed adult sex ratios. Males get in fights and die sooner, so the benefit cancels out.
Even if the theory did work here, you’d have to show that human behavior adapts to less-than-generational scale changes in sex ratio in a way that affects sex ratio at birth. The hypothesized response isn’t genetic evolution, it’s phenotypic plasticity. Somehow the observation that males were rare would have to get into the gonads. Possible, of course, but would need to be demonstrated.
I don’t have an alternative theory for the observed finding, except perhaps statistical noise. Small sample size. But the point is, I don’t think sex ratio evolution can explain it anyway.
Maybe more concise:
Female infant fitness = Prob(female survive to adulthood) x Adult_female_fitness
Male infant fitness = Prob(male survive to adulthood) x Adult_male_fitness
To keep things simple, say Prob(female survive to adulthood) = 1, and for males it’s 1/10. Since every female survives, and say the population is constant, then adult_female_fitness = 2. Since there are 10x more females than males, then average adult male fitness is 2 x 10 = 20. So
Female infant fitness = 1 x 2 = 2
Male infant fitness = 1/10 * 20 = 2
(The equality doesn’t depend on the exact numbers chosen.)
Giving birth to a female is just as valuable as giving birth to a male, so even sex ratios are favored. This is independent of adult mortality rates by sex.
I think I start to understand it (the argument is convincing, but real understanding is surprisingly hard). To know if my intuition is in the right track: should genes on sex chromosomes be able to heavily skew sex ratios? Intuitively I’d say yes
The Trivers-Willard Hypothesis ttps://en.wikipedia.org/wiki/Trivers–Willard_hypothesis states that female mammals are able to adjust their offspring sex ratio in response to their maternal condition. Red deer produce more sons when they are in good shape and more daughters when they are in bad condition. It makes sense that female red deer can change the sex ratio if they abort more males than females when times are very hard. How humans changed the sex ratio can be speculated about but I am not sure. What can be stated is humans did change the sex ratio in a statistically significant fashion multiple times. In a huge sample size, the countries of France and England during both World Wars had the sex ratio change.
I’m willing to believe the phenomenon is real. I know the Trivers Willard hypothesis; that doesn’t explain this phenomenon. Neither does higher male mortality. It’s not sufficient, anyway.
Not just at the end of wars but in the run up to wars and during. A phenomena noticed by the Greeks 2500 years ago. We can run a test case in the future by loading our front lines with social justice warriors instead which tend to be female.
I do not think they have the patience.
When the terrorists start going after these guys (and they will) they might just earn it.
I don’t think they ever will — terrorism operates on a different scale
i think they’ll… (censored cos superstitious)
“Most of these fallacies are addressed in the tome I’m perusing. The author correctly dismissed all of them. But then… ”
R.A. Fisher? Maybe this?
The Genetical Theory of Natural Selection
https://en.wikipedia.org/wiki/The_Genetical_Theory_of_Natural_Selection
It’s a new book! but Fisher wouldn’t have pulled any punches.
I recently found a copy in my university’s library, right next to its bigger, dopier cousin.
The structure of evolutionary theory is the worst book i’ve ever scanned through / was assigned a chapter to read in grad school. It is horrendous, even just as writing.
How does one explain the popularity of Gould then? He was the most popular writer of popular science in America for years.
I do credit him to finally persuading me of the reality and the principally genetic basis of IQ. I was quite resistant to the idea until TMOM.
Writing ability, popularity, and correctness all seem to be mutually orthogonal.
I haven’t read any of his popular science books. People say he is a “good writer”, and perhaps those books are much more readable, being directed toward a wider audience.
The Structure of Evolutionary Theory, in contrast, is 1400 pages long and appears to have no obvious audience at all. Certainly only the hyper-literate can read it, but I can’t imagine any self-respecting evolutionary theorist, or any other real scientist, reading more than 50 pages without going insane. I can imagine a very pretentious science book club full of English majors giving it a good review.
Here’s a gem of a paragraph on p. 31. This is representative of the book.
“As a primary theme for this one long argument, I claim that an “essence” of
Darwinian logic can be defined by the practical strategy defended in the first
section of this chapter: by specifying a set of minimal commitments, or broad
statements so essential to the central logic of the enterprise that disproof of any
item will effectively destroy the theory, whereas a substantial change to any item
will convert the theory into something still recognizable as within the Bauplan of
descent from its forebear, but as something sufficiently different to identify, if I
may use the obvious taxonomic metaphor, as a new subclade within the
monophyletic group. Using this premise, the long argument of this book then
proceeds according to three sequential claims that set the structure and order of my
subsequent chapters”
Gould is probably liked because he was a skilled writer (which is not the same thing as a good write) and made said things that lots of academics and publishers like to hear.
” I can’t imagine.. reading more than 50 pages without going insane” So, how many pages did you read?
If not B then not A. … but maybe my sanity is in question.
“significantly different in any trai that …”: who changed the spelling of ‘trait’? Does the blame lie with puppet Trump or string-puller Putin?
Will work well on marquees, but poorly in Scrabble…
In any society, real knowledge is distinct from social knowledge, by which I mean what must be known in order to survive, acquire resources, find mates. That changes, too, sometimes swiftly. After tyrants are deposed, we find that there were people behind those walls who knew the truth, but through wisdom or cowardice pretended something else was true. Nations can believe very untrue things for a very long time.
How far this can be stretched I don’t know. Every group does it at least some. It would seem that believing untrue things should have to be a disadvantage down the road. Yet look at the Russians, determined to install a new terrible government the moment they’ve kicked out the old one. We hope Kipling and his gods of the copybook headings will eventually be right. But perhaps Kipling was just a fool optimist as well. http://www.kiplingsociety.co.uk/poems_copybook.htm
Like it our not, Putin is probably the best leader Russia has had in a hundred years. Of course, that’s a pretty low bar to clear, but still true.
Alexander the Third is not amused.
Carl Zimmer has a book coming out in May.
https://www.panmacmillan.com/authors/carl-zimmer/she-has-her-mother-s-laugh
I’m still very interested in seeing the Fst value for dog breeds that corresponds to the 85% value for humans.
Intuitively I would think the value would be even higher, because the breeds diverged so recently. If this is in fact so, it would make a very powerful counter to Lewontin’s argument (powerful in the sense that the counter is precisely analogous to, and therefore precisely as understandable as, the original argument). Being able to say “Sure, 85% of human variation is within groups, But 90% of dog variation is within breeds, and look how different dog breeds are!” looks like a home run no matter who you are arguing with. But unfortunately I have yet to see an authoritative value for this number.
Lewontin’s Lewonkin would say that dog breeds were selected by humans rather than nature. Which is irrelevant, but the kind of argument they’d use.
70%.
Awww, too bad! It’s still a good argument, but not as immediately compelling.
Could you give me the source for that number? There might be some particular pairwise comparisons (e.g., poodles and bulldogs) that give a value higher than 85%, and you could make the argument based on that. (Remember, we are arguing with people who have a minimal understanding of genetics at best, so if we can force them to acknowledge that the 85% figure doesn’t mean what they thought it meant then we’ve pretty much done the best we can do here).
Time since divergence isn’t a great yardstick for guessing F_ST. If I’ve done my math right (which I’m not totally confident of), then the F_ST between my older sister’s kids and my younger sister’s kids has an expected value of 20% (i.e. 80% of the variance is within groups, 20% between) (that’s calculated assuming a large out-bred population). That’s higher than between Africans and Europeans, despite the fact that a good chunk of those genes will coalesce in only 2 steps back! How is that possible? Because although the variation between the two groups is sort of small, so is the variation within them – everyone in within a group shares parentage exactly. If you were to form two separate racial groups from my sisters’ progeny, it would be very easy to distinguish them genetically even many generations later. I think it would show up in phenotypes too: one group would be noticeably taller on average; the other noticeably smarter. The phenotypic distinctions wouldn’t be as obvious as black and white, but under the hood the genetic difference might be even more clear. (There is a difference here in that some of the differences between racial groups today are due to selection in different environments, whereas the differences in the family example are all due to drift.)
So why do dog breeds show higher F_ST between them than do human races, despite much more recent divergence? I think it’s simple: dog breeds are highly inbred compared to human. That greatly depresses within-breed variance, which pushes toward a higher F_ST.
Actually I think the F_ST is 1/9 = 0.11. Still not very confident about that though. That’s still similar to racial differences, but not as big as I said. I’m using the Time to Coalescence formula in here: https://en.wikipedia.org/wiki/Fixation_index. That formula is the expectation of F_ST given a large outbred population at genetic equilibrium, which may not actually hold for my sisters’ families. To get the actual F_ST requires doing the measurement.
This Time to Coalescence formula clarifies my point about dog breeds, btw. The formula is 1 – T_in / T_total, where T_in is the expected time to coalescence within-groups and T_total is the expected time to coalescence for the entire population as a whole. For dog breeds, the denominator is smaller than for humans (dog breeds diverged more recently than human races). But the numerator is even smaller still due to the small effective population sizes of dog breeds.
Quite remarkably, many deny behavioral differences in dog breeds. It gets really bizarre when veterinarians do it, but I suppose they must be at the confluence of social pressures.
Yes, especially with respect to pitbull behavior. Supposedly it’s caused by the way people train them. Mindboggling.
I knew a lab that wouldn’t even flinch, if you accidentally stepped on him. Meanwhile, someone I knew had a pitbull mix that would nearly leap at your throat if you once stepped softly near him – it was a very pampered dog. The lab was not fixed. The second dog was.
There is surely a possibility that these arguments can apply to differences between Indian castes…
redpillindian.blogspot.com
I was waiting for you to take on that article, ever since I made my (pretty popular) tweet storm on it:
Most people are stuck in the fst argument. It’s similar to double entry accounting. Most people can’t understand the logic of it too.
I have no idea where this notion originated
post WW2, in the educational indoctrination centers of the West.
prior to that, in the Communist Manifesto, which asserts a worldwide brotherhood of the Proletariat more powerful than any tribal, religious or linguistic connection between peoples.
otherwise, racial differentiation was widely understood and not even controversial well into the 20th century.
“there’s nothing in genetic theory or practice that supports the idea that polygenic traits can’t change rapidly”
if you have traits in balanced selection
and
if the more polygenic a trait is the smoother its bell curve is
then wouldn’t that make it easier to change rapidly?
i.e. if a trait only existed in big jumps then it couldn’t respond smoothly to small changes in selection pressure?
“Lately I’ve seen a few people arguing that there can’t be big between-population differences in highly polygenic traits, those influenced by many alleles of small effect, because evolution of a highly polygenic trait is for some unknown reason very slow – ‘at least 100 millennia to evolve appreciably’.”
Doesn’t it suffice to observe that the Breeder’s equation makes no reference to the size of effects, or number, of individual genes?
It basically assumes that a number of alleles influence, anywhere from a fair number to infinity. . Things are actually somewhat different if only one does.
Why would anyone say that you ca;t rapidly select on a highly polygenic trait? First reason is that most biologists or medico types known bloody nothing about selection. Second reason is that they’e got to say something, and they can’t say the truth.
There’s always more nonsense, by the way. Did you know that knowing the influential SNPS doesn’t count unless you deeply understand the whole biochemical mechanism associated with every one of them? That’s why nobody could select for cows that gave lots of milk before we knew everything to there was to know about the biochemistry of mild secretion
Guernsey cows are make-believe, just like elves, gremlins, and Eskimos.
I think the Breeder’s equation is generally first derived for a trait under control of a single gene, and then is generalized to an arbitrary number of genes.
my first car was a gremlin, so i know they exist.
Bad analogy. Holsteins produce more milk than Guernseys, which produce higher butterfat.
It’s a perfectly good analogy. Guenseys are dairy cows: most breeds of cows are not. I didn’t have to use the most extreme dairy breed in existence, did i?
according to one of my google safaris a while back Holsteins, Guernseys and Swiss Browns are the three breeds most selected for milk production which made me wonder if it was all due to intensive recent selection or if part of it was due to having the longest head start.
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“Most of these fallacies are addressed in the tome I’m perusing. ”
Could you indicate the author and title of the book? I would be very interested in getting a recommendation for a book on this subject.