Monday, October 15, 2007

Evolution in the Ashkenazi Jewish Population

 
Over at Eye on DNA Hsien-Hsien Lei has given over her blog over to Jon Entine to promote his new book Abraham's Children [Books About DNA: Abraham’s Children by Jon Entine].

Entine points out that Ashkenazi Jews (he is one) have higher frequencies of certain diseases like breast cancer, Tay-Sachs disease, Bloom's Syndrome etc. He notes, correctly, that Ashkenazi Jews are a relatively homogeneous population in spite of the fact that they are spread out over all of Europe and have since emigrated to North America and back to Israel.

There's nothing special about this group in terms of susceptibility to disease. Other genetically isolated populations, such as French Canadians, also have elevated incidences of some genetic diseases, and lower incidences of others. We usually assume that this altered frequency of alleles is due to random genetic drift: in this case the founder effect. Since the populations were founded by small numbers of people, there were certain alleles that just by chance happened to be over- or under-represented in the ancestors.

All reports suggest that Ashkenazi Jews descend from a small number of people who left the Middle East less than 2000 years ago. Possibly only four females contributed to most of the mitochondrial DNA in today's descendants (Behar et al. 2006). Most of these early descendants settled eventually in the Rhine Valley and from there they spread eastward. The main population expansion probably occurred after 1000 AD. Today their descendants number about 8,000,000 worldwide.

There is evidence for distinct subpopulations, suggesting a number of bottlenecks in the Middle ages (Feder et al. 2007).

Jon Entine is intrigued by stories that the Ashkenazi Jews have higher IQ's than many other ethnic groups. He offers the following speculation,
The book includes a chapter explaining the possible link between so-called Jewish diseases — certain neurological and LSD disorders, as well as DNA repair problems — and the high measured IQ of Ashkenazi (Eastern European origin) Jewry. Although this theory (most recently advanced by Gregory Cochran and Henry Harpending—two non-Jews—is best classified as informed speculation (as I acknowledge in the book) at the moment, it argues persuasively, I believe, that Ashkenazi Jews are a rather distinct population group in which positive selection pressures, balanced against the killer consequences of neurological disease mutations, have led to higher IQs. The “it’s environment and culture” argument are far less persuasive. This is only one chapter in the book–most of AC is a look at our shared Israelite ancestry and history–but it is the most provocative chapter. Wonder where others come down on this issue? Interestingly, “liberal” Jews (of which I’m one) are the one’s most uncomfortable about discussing or (even if they believe it) acknowledging this point.
Leaving aside the truth of the premise, it seems very unlikely that there was selection for higher IQ. We're dealing with a polygenic trait (intelligence) in a population of about 100,000 (average) over a maximum of 70 generations and possibly less than 25 generations. It's very unlikely that the adaptive benefit of a 10% increase in IQ would have an effect in that time frame.

Assuming there really is a genetic difference in intelligence then it is far more likely that it's due to the same factors that are responsible for differences in the allele frequencies of other alleles. It looks like the people in group that left the Middle East were smarter than the ones who stayed!


[Figure Credit: The image is Figure 2 in Behar et al. (2006)]

Behar, D.M. et al. (2006) The Matrilineal Ancestry of Ashkenazi Jewry: Portrait of a Recent Founder Event. Am. J. Hum. Genet. 78:487-497. [PubMed]

Feder, J., Ovadia, O., Glaser, B. and Mishmar, D. (2007) Ashkenazi Jewish mtDNA haplogroup distribution varies among distinct subpopulations: lessons of population substructure in a closed group. European Journal of Human Genetics 15:498–500. [PubMed]

23 comments:

  1. "It looks like the people in group that left the Middle East were smarter than the ones who stayed!"

    Oh man! you and your "just so" stories. :)

    Divalent

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  2. When your neighbors are bent on murdering you for some 1500 years, those of you who aren't smarter than average don't live to reproduce.

    Similarly, the well-known American Jewish tendency to depression probably has something to do with the fact that optimists didn't worry about pogroms, etc, enough to uproot their whole family and move to a foreign country where no one spoke their language. Heck, things would get better soon in Russia or Germany no need to see everything so darkly! Those with a more negative outlook on life did.

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  3. In the case of Tay Sachs and Gaucher disease (for example), there are multiple alleles that are associated with the disease and that have increased frequency in the Ashkenazi Jewish population. This means that the Founder Effect is not an adequate explanation for the prevalence of Tay Sachs and Gaucher in the Jewish population. There's a nice discussion of this point in Jared Diamond's article.

    Diamond, J. (1994) Nature 368:291-292

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  4. Stephen Spiro said...

    In the case of Tay Sachs and Gaucher disease (for example), there are multiple alleles that are associated with the disease and that have increased frequency in the Ashkenazi Jewish population. This means that the Founder Effect is not an adequate explanation for the prevalence of Tay Sachs and Gaucher in the Jewish population. There's a nice discussion of this point in Jared Diamond's article.

    Diamond, J. (1994) Nature 368:291-292


    It's no great surprise that Diamond seeks an adaptive explanation for these observations since he is an adaptationist.

    I prefer the analysis by Slatkin (2004) (Am J Hum Genet. 75: 282–293) who is well aware of the multiple alleles and their relationship. Here's the abstract.

    A founder effect can account for the presence of an allele at an unusually high frequency in an isolated population if the allele is selectively neutral and if all copies are identical by descent with a copy that either was carried by a founder individual or arose by mutation later. Here, a statistical test of both aspects of the founder-effect hypothesis is developed. The test is performed by a modified version of a program that implements the Slatkin-Bertorelle test of neutrality. The test is applied to several disease-associated alleles found predominantly in Ashkenazi Jews. Despite considerable uncertainty about the demographic history of Ashkenazi Jews and their ancestors, available genetic data are consistent with a founder effect resulting from a severe bottleneck in population size between a.d. 1100 and a.d. 1400 and an earlier bottleneck in a.d. 75, at the beginning of the Jewish Diaspora. The relatively high frequency of alleles causing four different lysosomal storage disorders, including Tay-Sachs disease and Gaucher disease, can be accounted for if the disease-associated alleles are recessive in their effects on reproductive fitness.

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  5. Um... Tay-Sachs is always fatal (infantile T-S in the pre-reproductive years). You don't get a more maladaptive condition than that. So, for the T-S alleles to remain in the population at a relatively fixed frequency, it seems likely that something other than drift is keeping those alleles around. Eventually deleterious recessives are... deleted, unless something useful results from having one of those alleles. So looking for a selective advantage associated with those alleles is not unreasonable.

    Also, seems to me that some of you have swallowed a rather hefty dose of credulity regarding "intelligence" tests and IQ tests, given that there are no universal definitions of human intelligence and no tests that reliably measure intelligence across ethnic or socioeconomic groups.

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  6. Missed this post first time round. Shouldn't it be possible to do a back-of-envelope calculation of the plausibility of the proposed selection on IQ?

    We have (claimed) estimates of the IQ differences between Ashkenazi and other Jewish populations. We have a time frame over which the selection is proposed to have occurred. We have estimates of the heritability of IQ.

    Wouldn't that be enough to allow us to estimate the necessary increase in reproductive success per additional IQ point if the selection hypothesis is correct?

    I don't have the right background to make the estimate myself, but I suspect you'll need some implausibly large pressure (several fold reproductive increase from a modest IQ change) to justify the selection hypothesis.

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  7. Pete says,

    I don't have the right background to make the estimate myself, but I suspect you'll need some implausibly large pressure (several fold reproductive increase from a modest IQ change) to justify the selection hypothesis.

    I agree. This is the problem with many adaptationist explanations.

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  8. Wouldn't this increased IQ be related to those with congenital adrenal hyperplasia with the 21-hydroxylase problem having the inability to make the cortisol axis so DHEA gets made without back regulation? I have noted in a few patients who were Ashkenazi that they had extremely high DHEA levels yet very low DHEAS levels so some inability to sulfate.It appears it takes DHEAS to keep the thymus in order and reports of thymus involution were noted in the adrenal hyperplasia patients.Yet when Heart Math foundation did the meditations which increased DHEA and DHEAS levels in a month the thymus GREW 70% and over time was quite enlarged.If one cannot convert their DHEA over to DHEAS then this would leave it for brain interface of DHEA increasing IQ and unfortunately leave much for testosterone conversion for the virilization and mean killer machine issues. That coupled with very low cortisol so knowing no fears.I found some studies showing XYY people from prisons all had this congenital adrenal hyperplasia. Wouldn't this be tragic to have people with no souls with high IQs with very high testosterone with NO empathy regulations?Perhaps to symbiotically get some cortisol they would feed off others who they create high fear levels hence cortisol levels in nonAshkenazi's.

    Do you know how to correct this inability to convert DHEA over to DHEAS in Ashkenazi Jews?Does it involve the cytochrome P450 system?

    Also if Ashkenazi have extremely high DHEA levels then would they not be immune to most bacterial and viral bioweapons unless they had an additional defective pathway?Isn't the cytic fibrosis pathway pretty limited?

    What is the exact pathway for conversion of aspartame over to formaldehyde?Does it require an enzyme system the congenital adrenal hyperplasia Ashkenazi do NOT have? or a phenyalanine pathway they do not have?

    What blood type is predominant for Ashkenazi?The ones I've known have all been A negative and had this adrenal/thymus issue.I know Cheney is A negative. I know Rumsfield, Bush and Cheney are Ashkenazi as well as most in their power group.
    Hitler's heritage was AshkeNAZI. Is this where we even got Nazi from?Perhaps they were working on breeding out so they were a soul less invincible, high IQ fighting machine.

    Perhaps a repair could be done to their DHEAS system so the thymus would repair itself. Epsom salts soaks help regular people sulfate more DHEA but what about the Ashkenazi? Would a liver/colon cleansing program help their situation?

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  9. I need to make another comment as now it gave me the option of this comment being sent to my email.I would appreciate your thoughts.

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  10. Projecting geometric population growth backwards: If the Ashkenazi population descended from four females about 2000 years ago, then even by 1000 AD they numbered less than ten thousand.

    In terms of historical import, the modern Jewish population didn't appear until after 1000 AD, which means it is genetically distinct from the population of Jews who lived in ancient Judah or even medieval Khazaria.

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  11. anonymous says,

    Projecting geometric population growth backwards: If the Ashkenazi population descended from four females about 2000 years ago, then even by 1000 AD they numbered less than ten thousand.

    Hmmm ... there seems to be two possibilities here. Either the authors of the study are really, really stupid not to have realized that, or your understanding of coalescence theory leaves a lot to be desired.

    I know which away I'd bet if given the chance.

    Hint: The fact that most mitochondrial DNA is derived from only four females does not mean that there were only four females contributing genes to the modern population.

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  12. Unfortunately Mr Morran, the above anonymous comment is right, it's mathematically impossible that a whole populations of circa 15 million people came exclusively from four women as the mainstream ashkenazi "science" claims, you just need a few insights on demography formulas to know it's a fallacious claim. first it's known that the doubling time in any human population can be summed up from the simple operation of dividing 70 by the demographic growth rate.

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  13. I'd like to give an example for those who are ignorant on this principle: Follow through my thoughts and tell me if this guy isn't right. let's take a primary population, as Ashkenazim say, of 4 females. If they were really middle eastern, and if they were really Israelites, you have to take into account that they live in a monogamous relationship. so it makes an original population of 8 people. that's OK, then let's estimate an average demographic growth rate for late Antiquity, for the whole Middle Ages and also for the Modern and Contemporaneous age. Jewish population growth rate has to be lower than the rest of the surrounding population, because, as they claim, they were uninterruptedly persecuted, murdered and victim of genocide. Even though I'll cheat for the Jewry and estimate it around 0.4% per year(really high rate, take into account that the maximum population growth that humankind as a whole has experienced was around 2.2%, and the highest population growth currently in a isolated area is circa 4.35%). OK so let's think according to the "mainstream" version of the history. Ashkenazim live in Europe since 1st century AD, then we have 2000 years util now (everyone knows it's surely much much less, but let's play the game Ashkenazim play). The doubling time(the time it takes for a population dubling it size) for Ashkenazi populaton is 175 years, approximately(70/0.4=175). Let's estimate how many times Ashkenazi population doubled its size; 2000/175 = 11.42, let's say 11. Now we elevate 2 to the power of 11 and we get 2048, 8x2048=16348. See, the current population of Ashkenazim is more than 15 million people, a myriad of people that is more than 917 times bigger than the estimated population. If you say that my line of thinking is flawed you have to reformulate the whole theory of population growth and destroy the idea "doubling time". The much bigger number of the current Ashkenazim population cannot be accounted for by any other explanation than that they are mainly not of Semitic genetic stock.

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  14. Around the year of 800 the population of Europe was around 27.5 million people, today it is circa 830 million people(according to the last census), so the growth of European population was about 2900%, and we have to take into account that there was a lot of gene flow between European populations and also coming from outside Europe. Let's talk about Ashkenazim then. Within a time of maybe 300 years more than the aforementioned span of time, Ashkenazim population growed from 8 to 15 million, a growth of 187499900%!!! How can this number be explained with earthly reason? Was it a work of Elohim? Even the statistics of 10 thousand resulting people is a drastically uneasy, we know that intense interbreeding (in such an insane and logically unconceivable way and degree that Ashkenazim claim) for such a long span of time is biologically, mathematically, historically and sociologically impossible. it requires much more than 8 people or 4, 5, 6, 7, 8 or nine maids for getting 10 thousand people 2000 years forward. 8 people acn engender 10 thousand only in the vacuum of mathematical principles, because in real world this attempt would end up in total failure. We are being generous saying that the claimed Ashkenazim stem population would lead to 10 thousand people currently, because such a totally hermetic interbreeding, as they want to claim, goes beyond the imagination and would go much beyond the label of "completely unhealthy", so unhealthy it would be that such "marital procedure" would make this population feeble and would doom it to extinction. Much more ridiculous is the claim when they say that such a few people were the only forefathers of an actual population of 15 million.

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  15. Ashkenazi Jewish population was almost non existent during Carolingian times(800 AD) if we compare it to Sephardic and Mizrahi populations. How can you explain millions of Ashkenazim who came out of thin air who added their masses to the expected 17 thousand Ahskenazi Jews to the present Era? No, they are not Sephardim who went to Central and Eastern Europe, because a tiny layer of Sephardic population chose exile than conversion, not all them were rich enough for affording it. Also Genetics shows that just very few Ashkenazim have Sepahrdic genetic markers (the richer ones, usually).

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  16. Mr Moran you just happen to contradict yourself, first you state in your article that Asheknazim are mostly "pure" descendants of original Hebrews, even quoting someone else, then you come up saying that a strong non-Jewish admixture explains why there aren't only 10000 Ashkenazim currently, make clear your point, we are not fools, we are not professional geneticists like you but we happen to have studied at least a little, even though one needs no deep study to notice your contradictions and to assess how unverifiable are your proposals. If there was such a huge gentile gene flow toward Ashkenazim stem community, then needly any reasonable person has to conclude that No, they're no way pure Hebrews, not even reaching the mark of "moderately Hebrews", the cauculation, and other simple, pragmatical and empirical evidences strengthens the claim that they are not even far from being real Semites, but they are diametrically opposed to Palestinians, Lebanese and Syrians. Anyone who visits a Ashkenazi family would never mix them up with Middle Easterns. Oh yes, look at Barbara Streisand and her Semitic facial traits identical to those you see in Sinai Peninsula people, isn't it? Not only this contributes for concluding their forgery, their culture is no way legitimately Middle Eastern. There are thousands of evidences that point out to an opposite direction than the one you expose here. It's really shameful sir, that a Professor of a famous University in North America is a completely sold out professional, pitiful how Western World is in clear decadence, really tragic panorama for seeing and knowing you can do nothing on it.

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  17. You know the "genetics" Website called Khazaria, right? That's surely a website for Zionist propaganda and disinformation. it claims that Ashkenazim are really closely related to Kurds and Palestinians, then How come do Ashkenazim have completely Central and Northeastern European phenotypes, at least almost all of them. Can you imagine a person like Henry Kissinger being a leader of Mujahideens in Iraq? A guy like Zac Efron being a suicide bomber in Palestine? or Max Born being a Sinai Bedouin? What you see speaks by itself.

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  18. You insinuate that there was a strong gentile gene flow to the Ashkenazim original population, but you never admit clearly that they are not pure Middle Eastern(a clear implication of your reposes to comments of your article) and would never consider admitting that they can be clearly considered not Semitic. I know that the Mitochondrial and Y dna that someone has today has originated thousands of years ago and would still be find in my ancestors who lived 10 thousand years BC. But do you have a reasonable explanation for why only "Semitic" haplogroups survived within Ashkenazim population, as you claim here? I've never heard of anything like that some Y and Mitochondrial haplogroups have dominance on others, that some are more prone and probable to be passed foward, and even worse, that haplogroups are influenced by the individuals' religion, that's a big WOW!

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  19. I have a Sephardic mother and when my friends come to know that I have a Jewish half, something I hardly ever tell someone, they cannot understand how Ashkenazim, even though "being from Middle East", they look totally Anglo-Saxon. Unfortunately only a few people have brains enough to reason on this issue. But for the luck of people like you, most of the world's population is incredibly dumb and ignorant. So you can be satisfied that you can put forward your mischievous plans. Good luck.

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  20. To my Sephardim brother João:

    Wow! what a rant.. I wonder if you an Anti-Zionist or just unaware of the remarkable contribution Sephardi have made to history.

    What Mr. Morran was saying is that mitochondrial DNA is passed down from mother to daughter only. This means that 40% of us arnt all descended from just 4 women, but that the other womens mDNA was outselected by means of only male offspring, or no offspring at all within the community.

    Genetics clearly shows that a full bred Ashkenazi Jew is 60% semitic regardless of particular region of origin, and Sephardim are far closer related to us then Mizrahim..We don't even need to talk about the Ethiopian or Chinese Jews.

    You make yourself seem like an idiot the way you argue a point. How do you know only the rich Ashkenazi are closley related to Sephardim? and all about the blood types? cmon really? and your use of how people look is simply ridiculous! I can still defend on your terms. Many Arabs are often hairy, so are Jews. Many Arabs often have big noses, so do Jews. Many Arabs have curly hair as it aids in cooling by keeping sweat on your head, what do you know? So do many Jews. Many Arabs are short... Well Freud may have been 6'1" with strait hair...BUT LOOK AT HIS FREAKING NOSE!

    I'm tired sry... I found this place randomly. I came upon it as I was researching about Fetal testosterone levels, because I've noticed a lot of Aspergers like traits in us.

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  21. Destiny Dreamers the Anti-Semite. sry..saol...or, um whatever your name was...Ironically it was him to got me linked here.

    No were not "killing machines"! Statistics show we have a far lower rate of committing violent crimes then gentiles. Yet we do probably have higher rates of mental illness..weird.

    Bush, Cheny, Rummsfeld, HITLER! HOW FUCKING DARE YOU! are/were not Jews.

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  22. Hoshko,

    Bush, Cheney, Rumsfled, and Hitler ARE/WERE Jews.

    Educate yourself on CRYPTO JEWS and then come back and post when you know what you're talking about.

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  23. Educate yourself on CRYPTO JEWS

    These are Semites engaged in unlocking codes, right?

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