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ng.3592-F1
A new paper in Nature Genetics, Characterization of Greater Middle Eastern genetic variation for enhanced disease gene discovery, is both interesting and important. But, as with the paper on the Andaman Islander genomes it starts out with a naive and misleading utilization of model -based clustering to frame the later results. Here’s a major offending section:

The least admixed samples were found in the NWA, AP, and PP subregions, suggesting that populations in these regions are derived from founder populations, but there was evidence of inter-regional variation in GME-specific components, suggesting the occurrence of local admixture (Fig. 1b) and potentially supporting historical events. The NWA component was found in regions from west to east across North Africa, likely representing the Berber genetic background…The AP component likely represents ancestral Arab populations and was observed in nearly all regions, possibly as a result of the Arab conquests of the seventh century coincident with the expansion of the Arabic language now spoken over much of the GME. Similarly, the Persian expansion into the TP and SD regions and parts of NEA in the fifth century was the most likely contributor of the PP signal.

Patterns of human migration and drift were recapitulated using TreeMix for GME subregions, on the basis of 1000 Genomes Project control populations…The inferred tree with no migration showed tight clusters for European and Asian populations but much greater apparent divergence among subjects from GME regions. T he ordering of the GME subregional populations from the root corroborated much of the ‘out-of-Africa’ ordering of subsequent founder populations…For GME populations, distance from the root emulated the west-to-east organization of GME samples, with the PP population showing the largest inferred drift parameter, supporting a west-to-east trajectory of human migrations.

You can’t assume that a population which is near fixed for a cluster, K, is actually not admixed. If you don’t have enough variation within your data set then the ‘least admixed’ populations will come out as similar to the reference, even though they themselves are admixed.

Second, I am quite open to the idea that the Arab conquests of the 7th century were demographically significant, but these results don’t show that. The Tuscan population is not 25% Arab, due to the Arab conquests. Additionally, Arabs did not permanently alter the interior of Anatolia. Their raids went rather rather far to the west, such as the one of Amorium, but the high water mark of Arab rule in relation to the Byzantines, arguably in the decades around ~800 A.D., simply resulted in a “no man’s land” along the borders (though some Semitic peoples, some of them Arabic speaking, of Christian background did migrate into Byzantium). Similarly, the Persian-Pakistani modal cluster has nothing to do really with the Persian Empire.

This is not a big deal, but, these passages are just silly. They’re wrong on the face of it. But the “peer reviewers” that Nature Genetics assigned to this paper were probably not well versed in human historical phylogenomics. Probably they saw that the methods were sound in the broadest sense (e.g., Admixture, Treemix, PCA, etc., are all fine methods), and were unaware that the inferences made were totally wrong. Anyone who had read Lazaridis’ et al.’s The genetic structure of the world’s first farmers would see how these passages needed to be revised and changed. The clusters in admixture above are to a great extent artifacts (useful ones for GWAS, but still artifacts). The historical inferences made have little basis in reality.

Second, the genetic pattern of variation above has nothing to do with the “out-of-Africa” migration. Rather, it has to do with the fact that there is cryptic Sub-Saharan African admixture even in the “pure” samples from some regions, because Sub-Saharan admixture is rather well mixed in some groups (e.g., in Northwest Africa). The cline is less about “out-of-Africa,” and more about a cline of African ancestry. These patterns of variation have literally nothing to say about the “out-of-Africa” migration. The whole passage should have been excised.

ng.3592-F3It’s a shame that there’s all this wrong stuff in the paper. I’m a big fan of Jean-Laurent Casanova because his medical genetics is going to make a difference in lives, and, his hairdo is awesome. Andy Clark is on the paper, he’s my St. Jerome for having co-authored Principles of Population Genetics. I feel a little ridiculous making these criticisms, but I think I’m right, and it’s a shame that the authors didn’t have anyone who knew enough human population genomics to fix this portion of the paper, and it’s a shame that Nature Genetics couldn’t find peer reviewers to steer them the right direction.

Aside from the the random wrong historical inference stuff, the paper is kind of a big deal (I think Nature Genetics worthy, but I don’t know anything about this stuff in regards to publications). It confirms in the broadest outlines a lot of what we knew. The further you go from Africa the less genetically diverse populations get when it comes to looking at polymorphism diversity. Native Americans have fewer segregating polymorphisms than Eurasian populations, for example. One way to model this is as serial bottlenecks out of Africa. I think that’s too simple of a picture, as there has been a lot of gene flow and admixture over the last 10,000 years, but on the coarsest of all scales it’s not totally misleading.

But a peculiar aspect of these dynamics is that when you look at runs of homozygosity in the genome, which usually measure more recent inbreeding, the Middle East and South Asia tends to have higher lower genetic diversity. To get a sense of South Asian populations, you can read The promise of disease gene discovery in South Asia. Because of caste/jati endogamy a lot of the South Asian groups have less genetic diversity than you might expect. This has disease implications.

Middle Eastern, North African, and Pakistani populations are even more extreme. You can see it in the figure above. Across short runs of homozogosity the results converge onto what you’d expect, roughly. But Middle Eastern populations are a huge anomaly at long runs. That’s because of this:

From 20–50% of all marriages in the GME are consanguineous (as compared with <0.2% in the Americas and Western Europe)1, 2, 3, with the majority between first cousins. This roughly 100-fold higher rate of consanguinity has correlated with roughly a doubling of the rate of recessive Mendelian disease19, 20. European, African, and East Asian 1000 Genomes Project populations all had medians for the estimated inbreeding coefficient (F) of ~0.005, whereas GME F values ranged from 0.059 to 0.098, with high variance within each population (Fig. 2c). Thus, measured F values were approximately 10- to 20-fold higher in GME populations, reflecting the shared genomic blocks common to all human populations. F values were dominated by structure from the immediate family rather than historical or population-wide data trends (Supplementary Fig. 8). Examination of the larger set of 1,794 exomes that included many parent–child trios also showed an overwhelming influence of structure from the immediate family, with offspring from first-cousin marriages displaying higher F values than those from non-consanguineous marriages (Fig. 2d).

Screenshot 2016-07-28 20.09.42 The authors masked alleles which were part of the reason that individuals were included in the data set in the first place (to prevent ascertainment bias). Rather, they were focused on genome-wide patterns of loss of function and derived alleles. Because they were looking at many low frequency variants naturally they found a lot of new variation, totally unobserved in European dominated genetic data sets. This is why bringing genomics to the world is kind of a big deal.

For me this was the most interesting, and sad, result:

Despite millennia of elevated rates of consanguinity in the GME, we detected no evidence for purging of recessive alleles. Instead, we detected large, rare homozygous blocks, distinct from the small homozygous blocks found in other populations, supporting the occurrence of recent consanguineous matings and allowing the identification of genes harboring putatively high-impact homozygous variants in healthy humans from this population. Applying the GME Variome to future sequencing projects for subjects originating from the GME could aid in the identification of causative genes with recessive variants across all classes of disease. The GME Variome is a publicly accessible resource that will facilitate a broad range of genomic studies in the GME and globally.

The theory is simple. If you have inbreeding, you bring together deleterious recessive alleles, and so they get exposed to selection. In this way you can purge the segregating genetic load. It works with plants. But humans, and complex animals in general, are not plants. More precisely the authors “compared the distributions of derived allele frequencies (DAFs) in GME and 1000 Genomes Project populations.” If the load was being purged the frequency of deleterious alleles should be lower in the inbreeding populations. It wasn’t.

Middle Easterners should stop marrying cousins to reduce the disease load. But that’s just a recommendation. Some of these nations, like Qatar, have a lot of money to throw at Mendelian diseases. Perhaps they’ll use preimplantation genetic diagnosis? I don’t know.

 
• Category: Science • Tags: Genomics, Inbreeding 
    []
  1. Cpluskx says:

    Questions:
    1) Can we know (by looking at this) when did inbreeding start in MENA?
    2) What are the effects of this on intelligence? (if any)
    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?

    Read More
    • Replies: @Razib Khan
    1) Can we know (by looking at this) when did inbreeding start in MENA?


    yes. would have to construct a model and see what parameters fit the data.

    2) What are the effects of this on intelligence? (if any)


    one generation of 1st cousin marriage (so that there aren't multiple generations of inbreeding) probably is a 5 pt IQ hit. some researchers say more. some say less.

    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?


    one generation. if the problem are deleterious recessively expressed alleles, then unrelated individuals should have different ones, and mask them. imagine if you cross two clonal (homozygous) individuals. their offspring could be highly heterozygous.
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  2. @Cpluskx
    Questions:
    1) Can we know (by looking at this) when did inbreeding start in MENA?
    2) What are the effects of this on intelligence? (if any)
    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?

    1) Can we know (by looking at this) when did inbreeding start in MENA?

    yes. would have to construct a model and see what parameters fit the data.

    2) What are the effects of this on intelligence? (if any)

    one generation of 1st cousin marriage (so that there aren’t multiple generations of inbreeding) probably is a 5 pt IQ hit. some researchers say more. some say less.

    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?

    one generation. if the problem are deleterious recessively expressed alleles, then unrelated individuals should have different ones, and mask them. imagine if you cross two clonal (homozygous) individuals. their offspring could be highly heterozygous.

    Read More
    • Replies: @Daniel H
    It is encouraging to know that the problems can be rectified if cousin marriage were ended.
    , @Talha
    Hey Razib,

    Can we know (by looking at this) when did inbreeding start in MENA?
     
    Knowing what we know about tribal societies (in broad patterns), isn't the more proper question to ask, when did various other societies stop being tribal - i.e. when did inbreeding stop in 'society/group X'?

    Thoughts...

    Peace.

  3. Daniel H says:
    @Razib Khan
    1) Can we know (by looking at this) when did inbreeding start in MENA?


    yes. would have to construct a model and see what parameters fit the data.

    2) What are the effects of this on intelligence? (if any)


    one generation of 1st cousin marriage (so that there aren't multiple generations of inbreeding) probably is a 5 pt IQ hit. some researchers say more. some say less.

    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?


    one generation. if the problem are deleterious recessively expressed alleles, then unrelated individuals should have different ones, and mask them. imagine if you cross two clonal (homozygous) individuals. their offspring could be highly heterozygous.

    It is encouraging to know that the problems can be rectified if cousin marriage were ended.

    Read More
  4. Anonymous says: • Disclaimer

    One thing I noticed working and living in the Gulf States was the number of Bedouin Arabs that are cross-eyed.

    I don’t mean like a wandering wild eye or crazy eyes, but a sort of divergent binocular focus like a Siamese cat (strabismus). I kind of assumed that this was due to inbreeding since fully 100% of them appear to have been married to a cousin, and their parents, ad infinitum.

    Read More
    • Replies: @Marcus
    I've read they struggle as pilots due to poor night vision. Look at what's happening in Yemen, the Saudi planes are afraid of the slightest AA fire and are limited to terrorizing civilian areas.
  5. It is really thrilling to know that we are importing that culture into the west.

    Read More
  6. Talha says:
    @Razib Khan
    1) Can we know (by looking at this) when did inbreeding start in MENA?


    yes. would have to construct a model and see what parameters fit the data.

    2) What are the effects of this on intelligence? (if any)


    one generation of 1st cousin marriage (so that there aren't multiple generations of inbreeding) probably is a 5 pt IQ hit. some researchers say more. some say less.

    3) How many generations withotu cousin marriage are needed to reduce the disease load significantly?


    one generation. if the problem are deleterious recessively expressed alleles, then unrelated individuals should have different ones, and mask them. imagine if you cross two clonal (homozygous) individuals. their offspring could be highly heterozygous.

    Hey Razib,

    Can we know (by looking at this) when did inbreeding start in MENA?

    Knowing what we know about tribal societies (in broad patterns), isn’t the more proper question to ask, when did various other societies stop being tribal – i.e. when did inbreeding stop in ‘society/group X’?

    Thoughts…

    Peace.

    Read More
    • Replies: @Razib Khan
    http://science.sciencemag.org/content/early/2016/07/13/science.aaf7943.full

    Examination of runs of homozygosity (ROH) above 500 kb in length in WC1 demonstrated that he shared a similar ROH distribution with European and Aegean Neolithics, as well as modern day Europeans (Fig. 3A, B). However, of all ancient samples considered, WC1 displays the lowest total length of short ROH, suggesting he was descended from a relatively large HG population. In contrast, the ROH distributions of the HG Kotias from Georgia, and Loschbour from Luxembourg indicate prolonged periods of small ancestral population size (8).


    ancient iranian farmers were as inbred as modern europeans; not so much. fwiw, i think inbreeding will have to decline in this region of the world as it goes through demographic transition. lots of people will not have marriageable cousins.
  7. @Talha
    Hey Razib,

    Can we know (by looking at this) when did inbreeding start in MENA?
     
    Knowing what we know about tribal societies (in broad patterns), isn't the more proper question to ask, when did various other societies stop being tribal - i.e. when did inbreeding stop in 'society/group X'?

    Thoughts...

    Peace.

    http://science.sciencemag.org/content/early/2016/07/13/science.aaf7943.full

    Examination of runs of homozygosity (ROH) above 500 kb in length in WC1 demonstrated that he shared a similar ROH distribution with European and Aegean Neolithics, as well as modern day Europeans (Fig. 3A, B). However, of all ancient samples considered, WC1 displays the lowest total length of short ROH, suggesting he was descended from a relatively large HG population. In contrast, the ROH distributions of the HG Kotias from Georgia, and Loschbour from Luxembourg indicate prolonged periods of small ancestral population size (8).

    ancient iranian farmers were as inbred as modern europeans; not so much. fwiw, i think inbreeding will have to decline in this region of the world as it goes through demographic transition. lots of people will not have marriageable cousins.

    Read More
    • Replies: @Talha
    Thanks for the info...and totally agree; the cousin thing needs to take a break for a bit for recalibration.

    Peace.
  8. Talha says:
    @Razib Khan
    http://science.sciencemag.org/content/early/2016/07/13/science.aaf7943.full

    Examination of runs of homozygosity (ROH) above 500 kb in length in WC1 demonstrated that he shared a similar ROH distribution with European and Aegean Neolithics, as well as modern day Europeans (Fig. 3A, B). However, of all ancient samples considered, WC1 displays the lowest total length of short ROH, suggesting he was descended from a relatively large HG population. In contrast, the ROH distributions of the HG Kotias from Georgia, and Loschbour from Luxembourg indicate prolonged periods of small ancestral population size (8).


    ancient iranian farmers were as inbred as modern europeans; not so much. fwiw, i think inbreeding will have to decline in this region of the world as it goes through demographic transition. lots of people will not have marriageable cousins.

    Thanks for the info…and totally agree; the cousin thing needs to take a break for a bit for recalibration.

    Peace.

    Read More
    • Replies: @mtn cur
    Hi Talha: I note that there are any number of good reasons why humans have not developed useful resistance to inbreeding. With many species which are both prolific and where misfires are easily concealed and disposed of, there are a few populations which are and generally the product of breeders who were incredibly observant. I have a few pigeons which are showing inbreeding depression now after about 20 generations of selecting the best individual male and female per hundred progeny. Obviously, the original breeder was well trained. I will do well not to blow the deal, which is what almost always the result when we amateurs come behind the master breeder with stock sense. I will hedge my bets by adding an aliquot of genes from the best of the original strain which was notable for inbreeding resistance.
  9. Matt_ says:

    Slightly grim reading. Back in the Genomic Patterns of Homozygosity in Worldwide Human Populations (http://blogs.discovermagazine.com/gnxp/2012/08/not-all-homozygosity-is-created-the-same-way/#.V5sEgPxrjIV) paper, some ME / South-Central Asia populations (Palestinian, Pathan, Sindhi) had medians of long ROH typical of Europe with extreme variations in the distribution, so it was more possible for me to think of those populations as having an outbreeding norm with some inbreeders in the population, and some isolated populations (Bedouin, Druze) who were more likely to show high inbreeding.

    However these ones show high medians and the non-consanguinous parentages also have relatively high medians of inbreeding coefficient (Fig 2d –
    http://www.nature.com/ng/journal/vaop/ncurrent/fig_tab/ng.3592_F2.html). And presumably these are sampled from the cosmopolitan parts of each region and not population isolates. So the norm seems more universal and widely practiced.

    Read More
  10. Shaikorth says:

    About the population history of MENA region. In Broushaki et al. tables (S24-25) the major difference between the pops that here get a “North African” component (Moroccans, Mozabites, Tunisian Berbers) and those that get an “Arabian” component (Saudis), besides West African-related stuff, is that the former greatly prefer European Neolithic – they’ll pick it over Anatolian Neolithic when given the choice – over Iranian Neolithic as haplotype donors. So how did the farmers go to Africa, through Europe?

    Saudis have an even or the opposite pattern of preferring Iranian Neolithic over Europe or Anatolia depending on the dataset, Egyptians intermediate. Another question is whether this is an old cline or a product of Islamic expansion.

    Read More
  11. Marcus says:
    @Anonymous
    One thing I noticed working and living in the Gulf States was the number of Bedouin Arabs that are cross-eyed.

    I don't mean like a wandering wild eye or crazy eyes, but a sort of divergent binocular focus like a Siamese cat (strabismus). I kind of assumed that this was due to inbreeding since fully 100% of them appear to have been married to a cousin, and their parents, ad infinitum.

    I’ve read they struggle as pilots due to poor night vision. Look at what’s happening in Yemen, the Saudi planes are afraid of the slightest AA fire and are limited to terrorizing civilian areas.

    Read More
  12. In terms of its effect on society, the IQ depression of inbreeding might be more significant than recessive disease.

    Are there any good estimates of the size of that depression? I have only seen a couple of smallish Indian studies.

    Read More
    • Replies: @reiner Tor
    Roughly 5 IQ points for first inbreeding generation (1st cousins), more if subsequently kinship coefficient increases with each successive inbreeding generation.
  13. Maybe I’m thick. But I don’t understand this:

    It works with plants. But humans, and complex animals in general, are not plants.

    Why not? I mean, I understand why we aren’t plants. What I don’t understand is why the purging theory doesn’t work with us?

    My expectation was that deleterious recessive alleles would be at lower frequencies (even if they had positive heterozygous effects). Why doesn’t it happen?

    Read More
    • Replies: @FKA Max
    This might be the explanation:

    THE EFFECTS OF INBREEDING AT LOCI WITH HETEROZYGOTE ADVANTAGE W. G. HILL AND ALAN ROBERTSON' Institute of Animal Genetics, Edinburgh 9 Received May 20, 1968

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1212065/pdf/615.pdf

    SINCE the early studies of FISHER and WRIGHT the theory of selection within populations of finite size has received much attention. KIMURA (1964) has reviewed the part of the theory that is based on continuous models in which it is usually assumed that individuals mate at random within small closed sub-popula- tions or lines. In such a situation we are concerned with the distribution of the frequency of individual genes over many replicate lines, or, equivalently, the distribution of the frequency of identical genes within the same line. In this report we study selection favouring heterozygous individuals with random mating within lines and no selection or crossing occurring between lines. The model for inbreeding which we discuss must be distinguished from an alternative situation, perhaps more common in plants, in which inbreeding occurs within an infinitely large population as a result of non-random mating, for example by selfing or mixed selfing and outcrossing. In the latter type of model, selection also may occur between sublines and recurrent mutation is not required for equilibria of gene frequency to occur without fixation, whereas it is in our
    model. These equilibrium situations have been analysed recently in some detail by ALLARD
    and co-workers. Many of their results for single loci are reviewed by JAIN and WORKMAN
    (1967) and analysis of a two locus model is given by JAIN and ALLARD (1966). The effect
    of selection for heterozygous individuals in small lines when there is no between-line selection has been studied by REEVE (1955) using transition probability matrices for mating types
    in lines of only a few individuals, and by ROBERTSON (1962). The latter considered two situations-firstly when there is a balance between mutation and fixation and secondly when, in the absence of mutation, the amount of heterozygosis is declining at a steady rate.
    In both, the critical factor proved to be the equilibrium gene frequency, which depends on the relative fitness of the two homozygotes. If the equilibrium frequency lies outside the range
    0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase
    the rate of fixation.

     

  14. @jimmyriddle
    In terms of its effect on society, the IQ depression of inbreeding might be more significant than recessive disease.

    Are there any good estimates of the size of that depression? I have only seen a couple of smallish Indian studies.

    Roughly 5 IQ points for first inbreeding generation (1st cousins), more if subsequently kinship coefficient increases with each successive inbreeding generation.

    Read More
  15. mtn cur says:
    @Talha
    Thanks for the info...and totally agree; the cousin thing needs to take a break for a bit for recalibration.

    Peace.

    Hi Talha: I note that there are any number of good reasons why humans have not developed useful resistance to inbreeding. With many species which are both prolific and where misfires are easily concealed and disposed of, there are a few populations which are and generally the product of breeders who were incredibly observant. I have a few pigeons which are showing inbreeding depression now after about 20 generations of selecting the best individual male and female per hundred progeny. Obviously, the original breeder was well trained. I will do well not to blow the deal, which is what almost always the result when we amateurs come behind the master breeder with stock sense. I will hedge my bets by adding an aliquot of genes from the best of the original strain which was notable for inbreeding resistance.

    Read More
    • Replies: @Talha
    Hey mtn cur,

    Very interesting notes on the pigeons; I suppose any breeder of horses, dogs, must be careful for these things. It certainly gives us a perspective from being able to see the effects on animals whose generations are like fast forward to us. I have a Senegalese friend who raises quails - I'll ask him about this.

    In clan or tribal societies, it provides for better social cohesion and, frankly, many people are still very tribal. And it seems, it is not so bad unless it is done to an extreme; hell even red meat or orange juice fall under this common sense rule. I mentioned this before, that Umar ibn al-Khattab (ra) advised people to avoid negative traits in progeny, when they appear through inbreeding, by telling one of the Companions, “Your offspring are becoming so thin and weak. Marry outside your close of kin.” Wisdom from the 7th century that people have ignored.

    Peace.
  16. FKA Max says:

    [hey now, Read More

    • Replies: @FKA Max
    Ok, thank you, Mr. Khan.

    I won't be citing him/the site on your blog anymore.
  17. Talha says:
    @mtn cur
    Hi Talha: I note that there are any number of good reasons why humans have not developed useful resistance to inbreeding. With many species which are both prolific and where misfires are easily concealed and disposed of, there are a few populations which are and generally the product of breeders who were incredibly observant. I have a few pigeons which are showing inbreeding depression now after about 20 generations of selecting the best individual male and female per hundred progeny. Obviously, the original breeder was well trained. I will do well not to blow the deal, which is what almost always the result when we amateurs come behind the master breeder with stock sense. I will hedge my bets by adding an aliquot of genes from the best of the original strain which was notable for inbreeding resistance.

    Hey mtn cur,

    Very interesting notes on the pigeons; I suppose any breeder of horses, dogs, must be careful for these things. It certainly gives us a perspective from being able to see the effects on animals whose generations are like fast forward to us. I have a Senegalese friend who raises quails – I’ll ask him about this.

    In clan or tribal societies, it provides for better social cohesion and, frankly, many people are still very tribal. And it seems, it is not so bad unless it is done to an extreme; hell even red meat or orange juice fall under this common sense rule. I mentioned this before, that Umar ibn al-Khattab (ra) advised people to avoid negative traits in progeny, when they appear through inbreeding, by telling one of the Companions, “Your offspring are becoming so thin and weak. Marry outside your close of kin.” Wisdom from the 7th century that people have ignored.

    Peace.

    Read More
    • Replies: @Anonymous
    It does raise a notion that "Tribal" is not necessarily obtuse. The Native American Population had many normal cultural features revolving around taking not only another tribes horse, but also their women. Strangers that appeared strong were often incorporated into the tribal society and those that had to leave were invited to sleep with many of the women. An example of this is the treatment the Slave member of the Lewis and Clark expedition, York, was given my the Mandan Tribe.

    Whether it is instinct, or observation, your comment on that wisdom is valid regardless of whether it is tribal.
  18. FKA Max says:
    @FKA Max
    [hey now, http://theunsilencedscience.blogspot.com uses a lot of quack statistics; also, the site is monomaniacal. when someone cite sources i find dodgy that informs my priors]

    Ok, thank you, Mr. Khan.

    I won’t be citing him/the site on your blog anymore.

    Read More
  19. higher lower genetic diversity

    Is this a typo or a reference to this sort of phenomenon? (Ans: Florida (minimax) and Wyoming(maximin) )

    Read More
  20. anon says: • Disclaimer

    “Middle easterners should stop marrying cousins to reduce the disease load.”

    And perhaps also to improve the low IQ’s of the region in general. First cousin marriages are yet one more reason for the backwardness found everywhere throughout the Arab world.

    Read More
  21. Twinkie says:

    Years ago during some research I was in the midst of reading a petition sent by a Roman centurion to the Senate. It contained the usual personal military history – where he was from, in what legion and cohort he served, how he was decorated and promoted, and where he settled after retirement and so forth. What struck then was his brief description of family history – he mentioned in the petition that his older brother gave a daughter to him as a wife! In other words, he married his niece, who subsequently gave him children. This was shocking to me at the time.

    I knew for example that while there were the occasional cousin or near-cousin marriages in China and Japan, Mongols were and have been highly exogamous (leading to the internally destructive practice of bride-kidnapping, which I think Genghis Khan forbade in his Yasagh to reduce strife and also due to his personal experience of his own wife, Borte, being kidnapped and possibly impregnated during the captivity). At one point, I think Koreans were not allowed to marry anyone with the same surname to the eighth degree of consanguinity or some such thing. So to read that a decorated Roman centurion (I think he was the first centurion of his legion, a highly coveted and substantial position for an “NCO”) mention so matter-of-factly that he was “given and married” his niece was so surprising (and eeky!) that I re-read that passage multiple times.

    Only later did I realize that inbreeding was very common in human history especially in the greater Middle East as well as pre-Christian Europe.

    Read More
    • Replies: @Anonymous
    Was the centurion in question an Italian?
    , @Shredni Vashtar
    Maternal Uncle-Niece marriages are fairly common among certain South Indian groups, including Brahmins. Is this, perhaps, less deleterious than cousins marrying each other? The same? Worse?
    , @BB753
    Uncle - niece marriages were "streng verboten" under Roman law.

    http://www.lesbelleslettres.com/livre/?GCOI=22510100852910
  22. Anonymous says: • Disclaimer
    @Twinkie
    Years ago during some research I was in the midst of reading a petition sent by a Roman centurion to the Senate. It contained the usual personal military history - where he was from, in what legion and cohort he served, how he was decorated and promoted, and where he settled after retirement and so forth. What struck then was his brief description of family history - he mentioned in the petition that his older brother gave a daughter to him as a wife! In other words, he married his niece, who subsequently gave him children. This was shocking to me at the time.

    I knew for example that while there were the occasional cousin or near-cousin marriages in China and Japan, Mongols were and have been highly exogamous (leading to the internally destructive practice of bride-kidnapping, which I think Genghis Khan forbade in his Yasagh to reduce strife and also due to his personal experience of his own wife, Borte, being kidnapped and possibly impregnated during the captivity). At one point, I think Koreans were not allowed to marry anyone with the same surname to the eighth degree of consanguinity or some such thing. So to read that a decorated Roman centurion (I think he was the first centurion of his legion, a highly coveted and substantial position for an "NCO") mention so matter-of-factly that he was "given and married" his niece was so surprising (and eeky!) that I re-read that passage multiple times.

    Only later did I realize that inbreeding was very common in human history especially in the greater Middle East as well as pre-Christian Europe.

    Was the centurion in question an Italian?

    Read More
    • Replies: @Twinkie

    Was the centurion in question an Italian?
     
    I think he was.
  23. AndrewR says:

    Slightly OT but isn’t it true that ideal mates are approximately in the third cousin range? I imagine this would be different among nore inbred populations.

    Read More
  24. …these passages are just silly. They’re wrong on the face of it. But the “peer reviewers” …

    Uh-oh.

    Do you know how many ‘Merkins are gonna be upset by comments like that? Doncha know that if it carries a label denoting it to be “scientifical” then it is written in gold, on stone? In fact, if it’s written, it must be the veritable word ‘o Gawd.

    For Heaven’s sake, what are you , some kinda radikal ‘er sumpin??? Dang, ain’t nuttin sakrid no more????

    ;)

    Read More
  25. @Twinkie
    Years ago during some research I was in the midst of reading a petition sent by a Roman centurion to the Senate. It contained the usual personal military history - where he was from, in what legion and cohort he served, how he was decorated and promoted, and where he settled after retirement and so forth. What struck then was his brief description of family history - he mentioned in the petition that his older brother gave a daughter to him as a wife! In other words, he married his niece, who subsequently gave him children. This was shocking to me at the time.

    I knew for example that while there were the occasional cousin or near-cousin marriages in China and Japan, Mongols were and have been highly exogamous (leading to the internally destructive practice of bride-kidnapping, which I think Genghis Khan forbade in his Yasagh to reduce strife and also due to his personal experience of his own wife, Borte, being kidnapped and possibly impregnated during the captivity). At one point, I think Koreans were not allowed to marry anyone with the same surname to the eighth degree of consanguinity or some such thing. So to read that a decorated Roman centurion (I think he was the first centurion of his legion, a highly coveted and substantial position for an "NCO") mention so matter-of-factly that he was "given and married" his niece was so surprising (and eeky!) that I re-read that passage multiple times.

    Only later did I realize that inbreeding was very common in human history especially in the greater Middle East as well as pre-Christian Europe.

    Maternal Uncle-Niece marriages are fairly common among certain South Indian groups, including Brahmins. Is this, perhaps, less deleterious than cousins marrying each other? The same? Worse?

    Read More
    • Replies: @Razib Khan
    it's worse. two times worse, as coefficient of relatedness is 2x closer than with first cousins.
  26. FKA Max says:
    @reiner Tor
    Maybe I'm thick. But I don't understand this:

    It works with plants. But humans, and complex animals in general, are not plants.
     
    Why not? I mean, I understand why we aren't plants. What I don't understand is why the purging theory doesn't work with us?

    My expectation was that deleterious recessive alleles would be at lower frequencies (even if they had positive heterozygous effects). Why doesn't it happen?

    This might be the explanation:

    THE EFFECTS OF INBREEDING AT LOCI WITH HETEROZYGOTE ADVANTAGE W. G. HILL AND ALAN ROBERTSON’ Institute of Animal Genetics, Edinburgh 9 Received May 20, 1968

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1212065/pdf/615.pdf

    SINCE the early studies of FISHER and WRIGHT the theory of selection within populations of finite size has received much attention. KIMURA (1964) has reviewed the part of the theory that is based on continuous models in which it is usually assumed that individuals mate at random within small closed sub-popula- tions or lines. In such a situation we are concerned with the distribution of the frequency of individual genes over many replicate lines, or, equivalently, the distribution of the frequency of identical genes within the same line. In this report we study selection favouring heterozygous individuals with random mating within lines and no selection or crossing occurring between lines. The model for inbreeding which we discuss must be distinguished from an alternative situation, perhaps more common in plants, in which inbreeding occurs within an infinitely large population as a result of non-random mating, for example by selfing or mixed selfing and outcrossing. In the latter type of model, selection also may occur between sublines and recurrent mutation is not required for equilibria of gene frequency to occur without fixation, whereas it is in our
    model. These equilibrium situations have been analysed recently in some detail by ALLARD
    and co-workers. Many of their results for single loci are reviewed by JAIN and WORKMAN
    (1967) and analysis of a two locus model is given by JAIN and ALLARD (1966). The effect
    of selection for heterozygous individuals in small lines when there is no between-line selection has been studied by REEVE (1955) using transition probability matrices for mating types
    in lines of only a few individuals, and by ROBERTSON (1962). The latter considered two situations-firstly when there is a balance between mutation and fixation and secondly when, in the absence of mutation, the amount of heterozygosis is declining at a steady rate.
    In both, the critical factor proved to be the equilibrium gene frequency, which depends on the relative fitness of the two homozygotes. If the equilibrium frequency lies outside the range
    0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase
    the rate of fixation.

    Read More
    • Replies: @reiner Tor
    Thanks for that!
    , @reiner Tor

    If the equilibrium frequency lies outside the range 0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase the rate of fixation.
     
    But wouldn't thatimply that in such populations there would be less recessive deleterious alleles? I still don't get it. Again, I might be slow, but there may be other readers who don't understand it either.
  27. @Shredni Vashtar
    Maternal Uncle-Niece marriages are fairly common among certain South Indian groups, including Brahmins. Is this, perhaps, less deleterious than cousins marrying each other? The same? Worse?

    it’s worse. two times worse, as coefficient of relatedness is 2x closer than with first cousins.

    Read More
    • Replies: @Twinkie

    it’s worse. two times worse, as coefficient of relatedness is 2x closer than with first cousins.
     
    And so so much ickier. I have nieces - they are like daughters to me. Even to imagine taking one as a wife is horrendously repulsive.
  28. Alfred says:

    It is amazing that Egypt seems to have been left out of this study. The population of Egypt in ancient times varied between 4 and 8 million people – a far greater number than that of any other country in the region.

    Read More
  29. BB753 says:
    @Twinkie
    Years ago during some research I was in the midst of reading a petition sent by a Roman centurion to the Senate. It contained the usual personal military history - where he was from, in what legion and cohort he served, how he was decorated and promoted, and where he settled after retirement and so forth. What struck then was his brief description of family history - he mentioned in the petition that his older brother gave a daughter to him as a wife! In other words, he married his niece, who subsequently gave him children. This was shocking to me at the time.

    I knew for example that while there were the occasional cousin or near-cousin marriages in China and Japan, Mongols were and have been highly exogamous (leading to the internally destructive practice of bride-kidnapping, which I think Genghis Khan forbade in his Yasagh to reduce strife and also due to his personal experience of his own wife, Borte, being kidnapped and possibly impregnated during the captivity). At one point, I think Koreans were not allowed to marry anyone with the same surname to the eighth degree of consanguinity or some such thing. So to read that a decorated Roman centurion (I think he was the first centurion of his legion, a highly coveted and substantial position for an "NCO") mention so matter-of-factly that he was "given and married" his niece was so surprising (and eeky!) that I re-read that passage multiple times.

    Only later did I realize that inbreeding was very common in human history especially in the greater Middle East as well as pre-Christian Europe.

    Uncle – niece marriages were “streng verboten” under Roman law.

    http://www.lesbelleslettres.com/livre/?GCOI=22510100852910

    Read More
    • Replies: @Twinkie

    Uncle – niece marriages were “streng verboten” under Roman law.
     
    Yet I think it happened enough times in reality in the pre-Christian Roman imperium that this highly decorated former centurion (he was settled on some farm on a frontier after being cashiered) mentioned it, rather matter-of-factly, as a part of his personal history. The specific wording, if I remember correctly, was "my elder brother gave me his daughter as a wife... she bore me several children." The marriage took place AFTER his retirement when he had a property to support a family. So he was possibly quite old (for the times). My thought at the time was that perhaps she was already married at some point and either her previous husband died or she was abanboned.
  30. Twinkie says:
    @Anonymous
    Was the centurion in question an Italian?

    Was the centurion in question an Italian?

    I think he was.

    Read More
  31. Twinkie says:
    @Razib Khan
    it's worse. two times worse, as coefficient of relatedness is 2x closer than with first cousins.

    it’s worse. two times worse, as coefficient of relatedness is 2x closer than with first cousins.

    And so so much ickier. I have nieces – they are like daughters to me. Even to imagine taking one as a wife is horrendously repulsive.

    Read More
  32. I would say that Egypt had a more heterogenous population and inbreeding would only be a problem within the monarchy/ruling groups of the era. You have inflow from North, South and West, with Tamazigh, various Nubian peoples forming the base of the commoners with an influz of foreign blood, whether Greek, Roman or Albania (Mamluk-recent early 19th century).

    It is obvious by and through phenotypic observation that Nassr, Sadat and other reflect the true Egypt as opposed to extremes of both sides, who are outliers and are more representativ of those who would typically ‘inbreed” as a way to preserve some illusory heritage or power continuim.

    Not unlike the Dominican Republic, where cousins of a certain type (racial) tend to marry each other a a way to preserve the illusory whitenes of being within an obvious bi-racial or tri-racial majority!

    Read More
    • Replies: @Razib Khan
    as i've explained at length: complex admixture doesn't have anything necessarily to do with inbreeding. inbreeding is recent mating between near relatives. you can be highly mixed, and still do that.

    i think it was an elite practice. but roman era records also suggest that commoners practiced incest. i suspect there's not much evidence in the genetic record because their fitness was lower compared to people in nonincestuous marriage. the egyptian histories record that consistent inbreeding did cause problems with royals.
  33. @jack shindo
    I would say that Egypt had a more heterogenous population and inbreeding would only be a problem within the monarchy/ruling groups of the era. You have inflow from North, South and West, with Tamazigh, various Nubian peoples forming the base of the commoners with an influz of foreign blood, whether Greek, Roman or Albania (Mamluk-recent early 19th century).

    It is obvious by and through phenotypic observation that Nassr, Sadat and other reflect the true Egypt as opposed to extremes of both sides, who are outliers and are more representativ of those who would typically 'inbreed" as a way to preserve some illusory heritage or power continuim.

    Not unlike the Dominican Republic, where cousins of a certain type (racial) tend to marry each other a a way to preserve the illusory whitenes of being within an obvious bi-racial or tri-racial majority!

    as i’ve explained at length: complex admixture doesn’t have anything necessarily to do with inbreeding. inbreeding is recent mating between near relatives. you can be highly mixed, and still do that.

    i think it was an elite practice. but roman era records also suggest that commoners practiced incest. i suspect there’s not much evidence in the genetic record because their fitness was lower compared to people in nonincestuous marriage. the egyptian histories record that consistent inbreeding did cause problems with royals.

    Read More
  34. Twinkie says:
    @BB753
    Uncle - niece marriages were "streng verboten" under Roman law.

    http://www.lesbelleslettres.com/livre/?GCOI=22510100852910

    Uncle – niece marriages were “streng verboten” under Roman law.

    Yet I think it happened enough times in reality in the pre-Christian Roman imperium that this highly decorated former centurion (he was settled on some farm on a frontier after being cashiered) mentioned it, rather matter-of-factly, as a part of his personal history. The specific wording, if I remember correctly, was “my elder brother gave me his daughter as a wife… she bore me several children.” The marriage took place AFTER his retirement when he had a property to support a family. So he was possibly quite old (for the times). My thought at the time was that perhaps she was already married at some point and either her previous husband died or she was abanboned.

    Read More
    • Replies: @reiner Tor
    His retirement was at age 40, the niece was maybe 20, so why would she have had a previous marriage?

    Probably as a soldier he first saw his niece at the time they got married.
  35. @FKA Max
    This might be the explanation:

    THE EFFECTS OF INBREEDING AT LOCI WITH HETEROZYGOTE ADVANTAGE W. G. HILL AND ALAN ROBERTSON' Institute of Animal Genetics, Edinburgh 9 Received May 20, 1968

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1212065/pdf/615.pdf

    SINCE the early studies of FISHER and WRIGHT the theory of selection within populations of finite size has received much attention. KIMURA (1964) has reviewed the part of the theory that is based on continuous models in which it is usually assumed that individuals mate at random within small closed sub-popula- tions or lines. In such a situation we are concerned with the distribution of the frequency of individual genes over many replicate lines, or, equivalently, the distribution of the frequency of identical genes within the same line. In this report we study selection favouring heterozygous individuals with random mating within lines and no selection or crossing occurring between lines. The model for inbreeding which we discuss must be distinguished from an alternative situation, perhaps more common in plants, in which inbreeding occurs within an infinitely large population as a result of non-random mating, for example by selfing or mixed selfing and outcrossing. In the latter type of model, selection also may occur between sublines and recurrent mutation is not required for equilibria of gene frequency to occur without fixation, whereas it is in our
    model. These equilibrium situations have been analysed recently in some detail by ALLARD
    and co-workers. Many of their results for single loci are reviewed by JAIN and WORKMAN
    (1967) and analysis of a two locus model is given by JAIN and ALLARD (1966). The effect
    of selection for heterozygous individuals in small lines when there is no between-line selection has been studied by REEVE (1955) using transition probability matrices for mating types
    in lines of only a few individuals, and by ROBERTSON (1962). The latter considered two situations-firstly when there is a balance between mutation and fixation and secondly when, in the absence of mutation, the amount of heterozygosis is declining at a steady rate.
    In both, the critical factor proved to be the equilibrium gene frequency, which depends on the relative fitness of the two homozygotes. If the equilibrium frequency lies outside the range
    0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase
    the rate of fixation.

     

    Thanks for that!

    Read More
  36. @FKA Max
    This might be the explanation:

    THE EFFECTS OF INBREEDING AT LOCI WITH HETEROZYGOTE ADVANTAGE W. G. HILL AND ALAN ROBERTSON' Institute of Animal Genetics, Edinburgh 9 Received May 20, 1968

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1212065/pdf/615.pdf

    SINCE the early studies of FISHER and WRIGHT the theory of selection within populations of finite size has received much attention. KIMURA (1964) has reviewed the part of the theory that is based on continuous models in which it is usually assumed that individuals mate at random within small closed sub-popula- tions or lines. In such a situation we are concerned with the distribution of the frequency of individual genes over many replicate lines, or, equivalently, the distribution of the frequency of identical genes within the same line. In this report we study selection favouring heterozygous individuals with random mating within lines and no selection or crossing occurring between lines. The model for inbreeding which we discuss must be distinguished from an alternative situation, perhaps more common in plants, in which inbreeding occurs within an infinitely large population as a result of non-random mating, for example by selfing or mixed selfing and outcrossing. In the latter type of model, selection also may occur between sublines and recurrent mutation is not required for equilibria of gene frequency to occur without fixation, whereas it is in our
    model. These equilibrium situations have been analysed recently in some detail by ALLARD
    and co-workers. Many of their results for single loci are reviewed by JAIN and WORKMAN
    (1967) and analysis of a two locus model is given by JAIN and ALLARD (1966). The effect
    of selection for heterozygous individuals in small lines when there is no between-line selection has been studied by REEVE (1955) using transition probability matrices for mating types
    in lines of only a few individuals, and by ROBERTSON (1962). The latter considered two situations-firstly when there is a balance between mutation and fixation and secondly when, in the absence of mutation, the amount of heterozygosis is declining at a steady rate.
    In both, the critical factor proved to be the equilibrium gene frequency, which depends on the relative fitness of the two homozygotes. If the equilibrium frequency lies outside the range
    0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase
    the rate of fixation.

     

    If the equilibrium frequency lies outside the range 0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase the rate of fixation.

    But wouldn’t thatimply that in such populations there would be less recessive deleterious alleles? I still don’t get it. Again, I might be slow, but there may be other readers who don’t understand it either.

    Read More
    • Replies: @FKA Max
    I am *not* an expert at all in this field, but how I understand this scenario to be possible is for carriers of homozygous, recessive genes (even deleterious ones) to just have much more children than anybody else in the population, i.e. polygamy, harems, etc. It probably boils down to money and power again. A forced and misguided, not voluntary and enlightened, selection for deleterious traits/genes so to speak, due to the high socio-economic and political status of the carrier of these deleterious alleles.

    Selection for light eye pigmentation is an example of voluntary, enlightened, beneficial selection of homozygous, recessive traits/genes, in my opinion, since light eyes are evolutionaryily advantageous in extreme northern or southern climates/latitudes far away from the equator.


    Effects of Homozygous Genes. The dominant trait for eye color is brown, represented by BB. All other eye colors – blue, grey, green, and hazel – are recessive traits, represented by bb. A homozygous brown eyed person would have the BB gene, while a homozygous blue eyed person would have the bb gene.
     
    - http://examples.yourdictionary.com/examples-of-homozygous.html

    Effect of Iris Pigmentation and Latitude on Chronotype and Sleep Timing


    Our group has previously noted three effects of light iris pigmentation in patients with seasonal affective disorder(summarized in Goel et al., 2002): (a) a larger summertime increase in photopic sensitivity than patients with darker pigmentation; (b) lower depression and fatigability scores in winter; and (c) earlier awakening during dawn simulation therapy
     
    - https://www.researchgate.net/publication/276058175_Effect_of_Iris_Pigmentation_and_Latitude_on_Chronotype_and_Sleep_Timing

    This is an uneducated guess and speculation on my part, but maybe Mr. Khan can help to bring some clarity to this issue, and if necessary correct me.

  37. @Twinkie

    Uncle – niece marriages were “streng verboten” under Roman law.
     
    Yet I think it happened enough times in reality in the pre-Christian Roman imperium that this highly decorated former centurion (he was settled on some farm on a frontier after being cashiered) mentioned it, rather matter-of-factly, as a part of his personal history. The specific wording, if I remember correctly, was "my elder brother gave me his daughter as a wife... she bore me several children." The marriage took place AFTER his retirement when he had a property to support a family. So he was possibly quite old (for the times). My thought at the time was that perhaps she was already married at some point and either her previous husband died or she was abanboned.

    His retirement was at age 40, the niece was maybe 20, so why would she have had a previous marriage?

    Probably as a soldier he first saw his niece at the time they got married.

    Read More
  38. FKA Max says:
    @reiner Tor

    If the equilibrium frequency lies outside the range 0.2 to 0.8 then selection may have an effect opposite to that usually expected and increase the rate of fixation.
     
    But wouldn't thatimply that in such populations there would be less recessive deleterious alleles? I still don't get it. Again, I might be slow, but there may be other readers who don't understand it either.

    I am *not* an expert at all in this field, but how I understand this scenario to be possible is for carriers of homozygous, recessive genes (even deleterious ones) to just have much more children than anybody else in the population, i.e. polygamy, harems, etc. It probably boils down to money and power again. A forced and misguided, not voluntary and enlightened, selection for deleterious traits/genes so to speak, due to the high socio-economic and political status of the carrier of these deleterious alleles.

    Selection for light eye pigmentation is an example of voluntary, enlightened, beneficial selection of homozygous, recessive traits/genes, in my opinion, since light eyes are evolutionaryily advantageous in extreme northern or southern climates/latitudes far away from the equator.

    Effects of Homozygous Genes. The dominant trait for eye color is brown, represented by BB. All other eye colors – blue, grey, green, and hazel – are recessive traits, represented by bb. A homozygous brown eyed person would have the BB gene, while a homozygous blue eyed person would have the bb gene.

    http://examples.yourdictionary.com/examples-of-homozygous.html

    Effect of Iris Pigmentation and Latitude on Chronotype and Sleep Timing

    Our group has previously noted three effects of light iris pigmentation in patients with seasonal affective disorder(summarized in Goel et al., 2002): (a) a larger summertime increase in photopic sensitivity than patients with darker pigmentation; (b) lower depression and fatigability scores in winter; and (c) earlier awakening during dawn simulation therapy

    https://www.researchgate.net/publication/276058175_Effect_of_Iris_Pigmentation_and_Latitude_on_Chronotype_and_Sleep_Timing

    This is an uneducated guess and speculation on my part, but maybe Mr. Khan can help to bring some clarity to this issue, and if necessary correct me.

    Read More
    • Replies: @FKA Max
    Another important aspect/dynamic to take into consideration in this context, in my opinion, is the following:

    Inbreeding and risk of late onset complex disease

    http://jmg.bmj.com/content/40/12/925.full

    The impact of inbreeding on reproduction, childhood mortality, and Mendelian disorders is well documented.2,3 In contrast, very little has been published on the effects of inbreeding on late onset diseases. This is despite the fact that inbreeding may have a greater influence on late onset traits than on traits that are subject to early selection.6,7 This study shows an important effect of inbreeding on several genetically complex late onset diseases which are of major public health importance.
     
    Later onset of complex disease has no immediate or early shock effect on the parents and family, and so they might not connect/associate their cousin-marriage customs with these family diseases. After all carriers of the these deleterious, recessive alleles usually reproduce when they seem to appear superficially and outwardly ''healthy''. Again, just speculation on my part, but I think this might be a reasonable explanation, for why cousin-marriage is still so popular in many parts of the Islamic world, because its negative effects and outcomes are often delayed and not immediately visible, and therefore families carry on these traditions, because they seem to offer greater benefits than disadvantages for the family (wealth/money stays in the family, and more family cohesion in general, etc.).

    PS: Sorry for the grammatical error in my above comment. It was supposed to say: have *many* more children than anybody else in the population ... Using less instead of fewer, is another one of the grammatical errors I regularly commit. I am trying to improve on this.
  39. FKA Max says:
    @FKA Max
    I am *not* an expert at all in this field, but how I understand this scenario to be possible is for carriers of homozygous, recessive genes (even deleterious ones) to just have much more children than anybody else in the population, i.e. polygamy, harems, etc. It probably boils down to money and power again. A forced and misguided, not voluntary and enlightened, selection for deleterious traits/genes so to speak, due to the high socio-economic and political status of the carrier of these deleterious alleles.

    Selection for light eye pigmentation is an example of voluntary, enlightened, beneficial selection of homozygous, recessive traits/genes, in my opinion, since light eyes are evolutionaryily advantageous in extreme northern or southern climates/latitudes far away from the equator.


    Effects of Homozygous Genes. The dominant trait for eye color is brown, represented by BB. All other eye colors – blue, grey, green, and hazel – are recessive traits, represented by bb. A homozygous brown eyed person would have the BB gene, while a homozygous blue eyed person would have the bb gene.
     
    - http://examples.yourdictionary.com/examples-of-homozygous.html

    Effect of Iris Pigmentation and Latitude on Chronotype and Sleep Timing


    Our group has previously noted three effects of light iris pigmentation in patients with seasonal affective disorder(summarized in Goel et al., 2002): (a) a larger summertime increase in photopic sensitivity than patients with darker pigmentation; (b) lower depression and fatigability scores in winter; and (c) earlier awakening during dawn simulation therapy
     
    - https://www.researchgate.net/publication/276058175_Effect_of_Iris_Pigmentation_and_Latitude_on_Chronotype_and_Sleep_Timing

    This is an uneducated guess and speculation on my part, but maybe Mr. Khan can help to bring some clarity to this issue, and if necessary correct me.

    Another important aspect/dynamic to take into consideration in this context, in my opinion, is the following:

    Inbreeding and risk of late onset complex disease

    http://jmg.bmj.com/content/40/12/925.full

    The impact of inbreeding on reproduction, childhood mortality, and Mendelian disorders is well documented.2,3 In contrast, very little has been published on the effects of inbreeding on late onset diseases. This is despite the fact that inbreeding may have a greater influence on late onset traits than on traits that are subject to early selection.6,7 This study shows an important effect of inbreeding on several genetically complex late onset diseases which are of major public health importance.

    Later onset of complex disease has no immediate or early shock effect on the parents and family, and so they might not connect/associate their cousin-marriage customs with these family diseases. After all carriers of the these deleterious, recessive alleles usually reproduce when they seem to appear superficially and outwardly ”healthy”. Again, just speculation on my part, but I think this might be a reasonable explanation, for why cousin-marriage is still so popular in many parts of the Islamic world, because its negative effects and outcomes are often delayed and not immediately visible, and therefore families carry on these traditions, because they seem to offer greater benefits than disadvantages for the family (wealth/money stays in the family, and more family cohesion in general, etc.).

    PS: Sorry for the grammatical error in my above comment. It was supposed to say: have *many* more children than anybody else in the population … Using less instead of fewer, is another one of the grammatical errors I regularly commit. I am trying to improve on this.

    Read More
  40. Anonymous says: • Disclaimer
    @Talha
    Hey mtn cur,

    Very interesting notes on the pigeons; I suppose any breeder of horses, dogs, must be careful for these things. It certainly gives us a perspective from being able to see the effects on animals whose generations are like fast forward to us. I have a Senegalese friend who raises quails - I'll ask him about this.

    In clan or tribal societies, it provides for better social cohesion and, frankly, many people are still very tribal. And it seems, it is not so bad unless it is done to an extreme; hell even red meat or orange juice fall under this common sense rule. I mentioned this before, that Umar ibn al-Khattab (ra) advised people to avoid negative traits in progeny, when they appear through inbreeding, by telling one of the Companions, “Your offspring are becoming so thin and weak. Marry outside your close of kin.” Wisdom from the 7th century that people have ignored.

    Peace.

    It does raise a notion that “Tribal” is not necessarily obtuse. The Native American Population had many normal cultural features revolving around taking not only another tribes horse, but also their women. Strangers that appeared strong were often incorporated into the tribal society and those that had to leave were invited to sleep with many of the women. An example of this is the treatment the Slave member of the Lewis and Clark expedition, York, was given my the Mandan Tribe.

    Whether it is instinct, or observation, your comment on that wisdom is valid regardless of whether it is tribal.

    Read More

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