Heterosis

Heterosis, hybrid vigor, is an increase in function in a hybrid offspring.  This effect is responsible for the greatest practical successes of genetics.  It has greatly increased the yield of maize, and, more recently, that of rice.   It’s also important in livestock breeding.

Probably the the most famous example is the mule, the offspring of a male donkey and a female horse.  Mules are hardier than horses,  have more endurance, and are stronger. They’re smarter than horses or donkeys.  They’re extremely useful in preindustrial agriculture- sterility is their only real disadvantage.

There are three main genetic explanations for heterosis.  One idea, the dominance hypothesis,  is that undesirable recessive alleles from one parent are masked by dominant alleles from the other parent.  The overdominance hypothesis states that two different alleles can have a positive effect that is greater than either alone.  The epistatic theory attributes heterosis to positive interactions between non-allelic genes.

Each of these patterns may occur in some cases, but on the whole it looks as if the dominance theory explains most of what we see.   Note that this is equivalent to a reduction in genetic load – and thus the success of hybrids might give us a general idea of how much advantage a zero-load individual might have.

Hybrid vigor is not something that always happens when you cross two fairly different parental strains. Sometimes you see reduced vigor (outbreeding depression).  But who wants that?  When you see a pronounced positive effect, the two parental lines are said to ‘nick’.  In general, this happens when the parental strains are genetically fairly distant.  But not too distant, of course. Note that this is a first-generation effect.

This suggests that crosses between particular human populations might produce superkids.  Clearly, there is no dramatic positive effect in any of the common crosses – we would have noticed.  I’ve seen a study that observed a moderate IQ advantage in Japanese-European kids in Hawaii,  something like a quarter of a standard deviation, but  I don’t think it’s been replicated, and that’s not enough change to get excited about in any event.

However.. there are crosses that have never been studied, quite likely because they’ve never occurred.  For example, the two human populations separated by the greatest genetic distance are probably Bushmen and Melanesians/Australian Aborigines: I’ve never heard of a cross and I doubt there has ever been one.

There’s no telling what would happen.

 

 

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120 Responses to Heterosis

  1. AlanL says:

    > the offspring of a male donkey and a female horse
    How does this work? Does he get some kind of box to stand on?

  2. j3morecharacters says:

    Before someone starts flying San people to the Australian Outback, let’s moderate his expectatives. San and Hindus, San and Dutch, etc. in one hand, and English and Aborigene cross on the other, quite frequent, did not produce remarkable individuals. But Spanish and Portuguese v. Africans did produce incredible musicians and mulatonas.

    • Patrick Boyle says:

      I looked up mulatonas. I was unfamiliar with the term. Apparently it is a certain kind of black female porn star. The women depicted do seem to have vigor but maybe not hybrid vigor. Maybe you meant something else?

      I wonder about black music. In Western music – perhaps I should say white music – there has been an evolution of greater and greater complexity. The musical forces got larger, the instruments became more complex, rhythmic and harmonic structure also got more complex. The only serious black music – Jazz – is quite primitive by these measures. It is like oral history versus real history.

      So I am disputing your observation that black Portuguese hybrids have shown any particular exceptionality much less that they have been seen to be incredible.

      BTW some musicologist think the increasing sophistication of serious Western music stopped in 1928. But that’s another issue.

      • dearieme says:

        Whereas enjoyable jazz lasted a bit longer.

      • reiner Tor says:

        Where does this 1928 come from? Richard Strauss died in 1949, Stravinsky died later but changed his style to atonal (I’m not sure how complex that was, but definitely not quite enjoyable), there might have been a few others.

        OTOH I think the most complex piece of music is Wagner’s Ring, and it was composed between 1848 and 1874. If you exclude it on the basis that it’s not one, but four pieces, then the title of Most Complex Musical Piece goes probably to Parsifal or Meistersinger, or maybe Götterdämmerung might still make it alone – even if you choose Parsifal, it would only add a few years since it was completed by 1882. If you exclude operas, you’ll probably choose something like Mahler’s Eighth Symphony, and it was composed in 1906, with the first performance coming maybe a few years later. Mahler died in 1911.

        So 1928 makes very little sense to me.

      • Patrick Boyle says:

        The way this software works I can’t respond to the people who responded to me so I have to comment on my own comment. Sub-optimal.

        Jazz has a favorable reputation but in fact is not very popular even with blacks. The idea that jazz is a high art form seems to me to be an urban legend or a piece of politically correct propaganda.

        I read the 1928 date in an article on physics which claimed that physics ceased to develop after 1928 just as music had. I’ll try to find it. For years I advised everyone not to listen to any music written after 1791 – but that’s just me.

        I’d love to write more but this is a genetics blog and I don’t want to hijack the discussion.

      • reiner Tor says:

        I disagree, most interesting music was actually composed after 1791. At least that’s how it’s working out to me.

      • Patrick Boyle says:

        Mr. Tor, you mistake me. I know the Ring very well. I’ve sung two roles in the Ring. I advised people to only listen to music from Monteverdi to Mozart for heath reasons, not esthetic ones. Older music is soothing. It lowers your blood pressure. I’m fond of Hindemith but Boccherini is better for me.

      • little spoon says:

        Why does complex even count as the highest measure musical talent?

        Jazz might be dead now, but classical music as a “high art” is too for the time being. Sometimes we get a pretty good soundtrack composer like Mancini, Morricone or sometimes Elfman etc. For the most part, I think good soundtrack composers could incorporate the best ideas of jazz.

        The reason that jazz was ever considered a high art may be that so many of the great classical players of the time admired it and some tried to study it. They say Rachmaninov thought Art Tatum was the greatest pianist in any style. Whose opinion am I supposed to believe? Rachmaninov’s or Patrick and Reiner’s?

    • norkuat says:

      Although I disagree in your preference towards mulattoes, the miscegenation of blacks and Iberians surely have contributed in phenomenal soccer players! But in Usa you don´t care about that..

    • little spoon says:

      Half black half Indian people have interesting singing voices. I am not sure I’d call them better than an african american singing voice, but it is different sounding- oftentimes a bit more feminine and smoother. Something that may help half indian and half blacks is that they look black to most people. Nikki minaj, one of the TLC girls and Melanie fiona are half South Asian half black. Beyond that Rihanna might be part Indian considering how their parents look and where they come from.

      Norah Jones is another one that gets by on minimal musical talent but a really good voice. I don’t know if they’d get as far if there were more half indians singing in our culture but they get a leg up in the recording industry just for sounding unusual.

  3. “Note that this is a first-generation effect.” And in subsequent generations that one time advantage is retained, or fades back to the mean of the original populations?

    • gcochran9 says:

      Not retained. There can be long-term advantages from populations mixing, say if some favorable genes are added to the mix and increase in frequency over time, but hybrid vigor is basically a first-generation effect. That’s when you have maximal heterozygosity.

      So, if we did find that two obscure human populations generated super kids, we’d have to keep going back to the original populations to generate more. Since those obscure populations have low population size (Bushmen, Pygmies, Australian aborigines, Andaman Islanders, Mamanwa, Mohicans) these superkids would be a scarce and valuable resource. Great Powers would try to monopolize the sources: the US would decide that the Australian Aborigines were being horribly mistreated and all needed asylum in the US. And so on. Some countries with such valuable local genetic resources would manage to keep hold of them and demand high rents: they’d be like Kuwait or the UAE. Probably, after a while, those superkids would take over in some countries, rather like the Mamelukes in Egypt. Since they don’t breed true, continued access to the paternal and maternal stocks would be a continuing national security issue…

  4. dave chamberlin says:

    The text books on human evolution typically inform us that 70,000 years ago there was an extreme human bottleneck and that quite possible because of a super volcano that occurred right about then we almost went extinct. Doesn’t this strike you as odd? Here we were a slowly evolving bunch of hominids over a period of millions of years getting a little bit smarter, growing brains a little bit bigger and then right about the time we gained modern intelligence we almost went kaput.

    Hmmmmm. What other explanation could there possibly be for this human bottleneck? Well, it has been discovered in the last decade that almost all of humanity is a small percentage neanderthal so it would seem a far more likely explanation for this extreme bottleneck that heterosis or hybrid vigor occurred when a small population hybridized with neanderthal and with the resulting intellectual advantages the population exploded and pretty much took over the world.

    But there is a problem, not with the theory, the theory hold up just fine, it is with political ramifications. It seems that part of humanity south of the Sahara doesn’t have this small percentage Neanderthal so lets just keep the text books as they are.

    • reiner Tor says:

      I’m wondering if the bottleneck really was a bottleneck or if it was just that this small group conquered and mostly exterminated the rest. The latter scenario looks a lot more plausible to me.

      • Anonymous says:

        “I’m wondering if the bottleneck really was a bottleneck or if it was just that this small group conquered and mostly exterminated the rest”. Technically,_that_would be as good a bottleneck as any other.

    • dave chamberlin says:

      Way back yonder in 2005 a brilliant researcher named Bruce Lahn wrote a paper where he found that a gene that influenced brain growth had been introduced into the human gene pool way back yonder 37,000 years ago, that was a very approximate date, it could have been a lot earlier. He determined that the gene was approximately 800,000 years old so he hypothesized it came from another archaic species of hominid we interbred with. He then went looking for where this gene was to be found and he discovered that it had spread all around the world except for Africa south of the Sahara. I went looking through the internet to see who else was excited by this paper and I found Razib Kahn, and I have been a loyal reader of his blog ever since. Greg Cochran can tell you in greater detail the reward Bruce Lahn received for his ground breaking paper. He caught holy hell for having the audacity to suggest that there is variation in the human gene pool that influences brain function. He lost, or was pressured to the point that he quit his position as a lead researcher for the prestigious and well funded Howard Hughes Institute and now works in China. I hope someday Bruce Lahn will get the credit he deserves and that researchers like him will be encouraged rather than discouraged.

      • Difference Maker says:

        Yes. I remember it was a tremendously awkward finding before my full awakening. I believe he has done some interesting research into mitochondria as well

      • dave chamberlin says:

        I have a suspicion Bruce Lahn did not abandon his research that got him in hot water in the United States. If he is the ambitious genius I think he is he has picked up right where he left off with his research at Howard Hughes with better funding and a bigger smarter staff working under him in China. He told the United States press he is changing the focus of his research when he goes back to China, but I don’t believe it. Time will tell, time will tell. Are they going to update us what they are doing with submissions to our most prestigious journals? Nope, not a chance. The United States will continue to fund more sophisticated weapons, but what do you think China and Russia will fund? Whatever gives them the brightest future is my guess and if I was China I’d give scientists like Bruce Lahn a blank check. Just my perspective.

  5. JayMan says:

    Well, my wife and I are doing our part, lack of outstanding effects notwithstanding. :p That said, there are a few mutations we each carry that we’re hoping to cancel…

    • Mark says:

      We’ve been running that experiment for centuries now in the New World. There’s no indication of exceptional ability. There is evidence though of greater intelligence relative to purer blacks and thus a greater ability to exploit affirmative action and other opportunities afforded to blacks in general.

      • JayMan says:

        I think you’re missing something here…

      • Anthony says:

        “There’s no indication of exceptional ability.”

        There’s no indication of exceptional *intelligence*. While it seems that children of one black and one white parent tend to have intelligence levels which average around the average between the black and white populations, they do seem to have other advantages such that the population average of 50/50 mixes is somewhat better than the average of the two populations.

      • WW says:

        “they do seem to have other advantages such that the population average of 50/50 mixes is somewhat better than the average of the two populations.”

        Mulattoes tend to be like blacks. They tend to be below the white average.

  6. There is a lot of evolutionary distance between whites and Australian blacks, and crossbreeding clearly does not produce hybrid vigor.

    • Tomás says:

      Effectively, what you notice again and again in the field is “averagedness”. There have been, indeed, all kind of crosses, much more of what is usually brought to mind, and there have not been no improved individuals, only “averagedness”.

      On the other hand, there have been detected some instances of outbreeding depression (excest? ex(o)sanguinity?) that have been explained resorting just to one explanatory cause: the stress of being raised as a mongrel. I do really believe in the added stress of having a mixed identity, but the health effects could have more causes. Clearly, one of them could be outbreeding depression. Strong outbreeding depression has been detected in invertebrates, fishes, birds and mammals (oryx). It would be perfectly possible to find it in humans as well. Obviously, as far as I know, it’s not been investigated in humans. Everyone can imagine the storm that such an investigation could arise.

  7. Toad says:

    greatest practical successes of genetics … greatly increased the yield of maize

    Maybe the recent obesity epidemic is actually hybrid vigor.

    From the standpoint of aliens breeding humans as livestock, were improving as a breed. Were getting bigger. Increased meat yield per capita. We’ve gone from select to prime. Extra fat gives us the energy to pull carts on long journeys without food.

  8. Ambacti says:

    According to wikipedia the last common ancestor of horses, donkeys and zebras existed 4 – 4.5 mya. Bushmen and Melanesians are seperated by 200,000 years at most. Whatever hybrid vigour is exhibited probably won’t make up for the 3 SD IQ difference between us and them, even if we selected particularly gifted individuals.

    I have always been fascinated by the “archaic” Australasian peoples. Since they all belong to mtdna haplogroup L3, specifically a branch of subgroup N which took off east long before the others, is it fair to assume that they are comparable in intelligence, behavior and appearance to the original L3’s that migrated out of Africa? Intelligence is a valuable advantage to a hominin, it’s pretty much all we’ve got, so I doubt that they could have regressed. I had once imagined the first out of Africa to have been somehow exceptional, but in reality we must have looked a sorry bunch of savages, modern Melanesians and Bushmen would probably appear culturally refined and technologically sophisticated by comparison.

  9. Greying Wanderer says:

    Shouldn’t this apply to the Cape Colored population of South Africa?

    • Tomás says:

      Even another example more of ‘averagedness’. I can’t really find examples of hybrid vigor in humans. Not even those usually put forward by cognitive reductionists (northern europeans with far east asians). There’s no hybrid vigor on the field.

  10. Toad says:

    Ligers, tigons, and polizzlys oh my!

  11. KevinM says:

    We’ve been doing that experiment here in Houston. Population size in the high 100s low Ks. Smart Han with smart Anglo or Criollo reliably yields hybrid vigor. Enough so that it’s a common joke/barb between purebloods and the parents of the mixadas. Unfair advantage getting into the best kindergarten and all that.

    Seems to be like a .5 STD boost in g, but more noticeably a removal of whatever mental shortcoming that keeps the Han’s performance down.

    Doesn’t work for the Vietnamese; other E Asian populations here are too small or don’t interbreed (looking at you Patel) to tell one way or another.

    • bleach says:

      “Seems to be like a .5 STD boost in g”
      Thanks you professor. Of course you have zero evidence actually backing this up, but I’m sure we can all trust your subjective observation is a fair ballpark number, and not at all about a nerd with an Asian fetish seeing what he wants to see.

      • Tomás says:

        The asian fetish in some male europeans should be really investigated in a scientific way. I know there have been some hypothesis, like higher neoteny processed as a very feminine trait.

        Why do I say this? Because to me (and yes, this is a subjective impression, but one that comes from years of observations) there are two big blunt groups of male europeans: a (maybe big) minority that shows a strong fetish for asian women and the rest, who not only don’t find asian women specially desirable, but even somewhat strange.

        This is an observation I had for the first time decades ago, when I was a teenager. Some friends of mine used to find asian women very femenine. For me and others, they were (and are) exactly the opposite. Even those asian models or actresses usually regarded as very beautiful seem really weird to some of us. On the other hand, some other euros find them very attractive. Both reactions are so marked that I sometimes think there has to be some biological mechanism underlying these behaviors. In general, I cannot find them attractive. Not even when I wishfully try in a “experimental” way. I simply cannot understand this fetish,

  12. As regards the Spanish and Portuguese music, the influence of Gypsies may have been a greater factor.

    As dave chamberlin suggested, this may be true and have already occurred. I’m betting against the last few mixtures being dramatic, because there aren’t encouraging signs in the other, somewhat nearer crosses. Still it’s fun to know it’s possible and something to think about.

  13. j3morecharacters says:

    Searching for clues in history, “pure breeds” were invariably deemed superior and mixed multitudes as inferior. In the Hellenistic world, pure Macedonian ancestry was appreciated to the point that rulers married their sisters. All aristocracies tend to endogamy. Which, of course, proves nothing. Or does it?

    • SpaghettiMeatball says:

      Hey, J, nice to see you here!!

      But think about this: The most mixed people on earth are the ashkenazi jews, they have middle eastern, european, and even asian and african blood. And yet they are the smartest people also. So maybe “pure breeds” are not all that?

    • SpaghettiMeatball says:

      Bleach, there was an admixture analysis dienekes (or one of the other genome-bloggers) did, that showed ashkenazi jews having at least 6 colored bars in their bar plot (like the one greg posted earlier).

      They had green, blue, purple, red, orange…god knows what else. Their ancestry looked like a rainbow. These people have been all over west eurasia during their history. What would you expect them to be like?

      • sarkomere says:

        And how about this?

      • Matt says:

        Ashkenazis and Sephardis tend to be more split between most of the clusters than a lot of other populations, but about the same and in the same proportions as the Sicilian people (and to a lesser extent other Greek and Italian people) who they seem most similar to.

    • SpaghettiMeatball says:

      Yeah. You guys are right. I should have rephrased that. Obviously the mixture in jews is not of populations as differentiated as, say, africans and japanese. They are more a mixture of different west eurasian, or caucasoid if you will, elements. But still it is something that a fanatic nazi (in the literal, not the internet sense) would refer to as bastardization, as our friend Sarkomere shows us.
      And that bastardization did not hurt the jewish people one bit.

      • Difference Maker says:

        The Askhenazim underwent selection and are extremely inbred. It is possible they picked up advantageous alleles from other populations, but nevertheless they have since bottlenecked. Need more purifying selection to iron out all the harmful variants (Tay-Sachs etc). I’m sure many could benefit from being better looking, having more balanced characters and being more athletic

        As for nobility, it is a matter of preserving a winning genetic recipe that enabled them to conquer other peoples. Getting rid of genetic load. So you see, it is a matter of some importance – just as the selection for intelligence in Ashkenazim was, otherwise they’d be mere mediocre mongrels

    • Tomás says:

      I just took a look at those links, but they seem very interesting instances of outbreeding depression.

      In recent years there have been some studies, usually by conservation ecologists and biologists about the impact of outbreeding depression. In their highly specialized field it’s a somewhat important question, given that sometimes they have to balance the benefits and downsides of introducing alogen individuals in reduced populations of animals risking extinction. On the one hand, you could avert ‘inbreeding depression’. On the other, you risk outbreeding depression and, of course, the lost of specificity (distinctive identity) of the endangered group. You could even end having both, inbreeding and outbreeding depression, at the same time. It happened with the oryx reintroduced in the arabian peninsula.

      These studies have shown that outbreeding depression is cleary a far more common process than previously thought.

  14. Anonymous says:

    Since “outcrossing” is and always was a prominent arrow in mother natures quiver, it has to be of great value to a species survival. And the probability that a gene introduced from a different species is positive in effect is certainly much higher than that a random mutation is. Just as modern humans carry parts of the neanderthal genome, more and more species have been found out to have gained heterosis from interspecies hybridisation, In the genome of american bison influx of genes of the yak have been found, whereas european bison (wisent) from the aurochs(ancestral cattle).Crosses between different species do occur without human interference quite often, If the offspring is fertile and the caputured genes offer an advantage they will stay in the population.Exchange between very different strains of bacteria(conjugation) is commonplace and the reason resistance to antibiotics spreads so fast among these asexual organisms. Circus lions and cattle both show the effects of few founder animals and selection not towards fitness in a wild environement but towards manageability by humans, the indian zoo- lions where most probably heavily inbreed, like modern dog breeds. Crossing san and aborigines might result und people extraordinarily well adapted to hunting in arid country, but why should they be better at calculus????

  15. TWS says:

    So with a sd increase we’d IQs of what, 80? We’re not starting from a high spot here.

  16. Sandgroper says:

    When my mother-in-law was a kid in northern China, she had a pet mule.

    That’s totally irrelevant to the topic, I just think it’s interesting. I had pet kangaroos, a pet dingo and a pet flock of Khaki Campbell ducks, but never a pet mule.

    I knew plenty of people who had pet lambs, but they always ate them when they got big enough. My daughter tells me there is no contradiction in eating your own pets, but she’s half Chinese.

    When my daughter was copping racist garbage from both directions when she was a little kid, I taught her about heterosis. That worked in boosting her self-esteem for a while, until she thought to ask “Well, if I’m an example of hybrid vigour, why do I get hay fever, then?” It worked with IQ though, she didn’t regress to the mean, she outstripped both me and my wife.

    • TWS says:

      I got your mother in law beat. We had a badger, a coyote, and a wild turtle (or tortiose I don’t know which). Not at the same time though. Nothing exotic like a kangaroo. Now that would be something.

      • Sandgroper says:

        Baby kangaroos are fun – if you hold open a sugar bag, they will dive in head first and go to sleep, like they do with their mother’s pouch. I envy you the coyote – I’d love to know how they differ from domestic dogs in terms of their behaviour around humans.

      • TWS says:

        Badly. They are ok outside dogs but too smart for their own good. We had a rotti too. Every morning she’d get scolded for getting into the garbage. One night I get up and slip into the kitchen to watch the coyote taking items from the garbage and placing them around the rotti while the rott looked miserable.

        I scolded Wile who acted like he’d done nothing wrong. The dog looked miserable like the scolding was for her. Neighbors hit him with the car. I think on purpose. He was almost always indifferent in a way dogs just aren’t. He just didn’t do dominance most of the time. He was too small to be top dog but just didn’t care unless you were serious.

    • The fourth doorman of the apocalypse says:

      When I was in my teens I had a pet Major Mitchell. Picked it up in Cunnamulla and transported it to Darwin. It eventually made its way back to Qld with some help.

      • Sandgroper says:

        Don’t see many pet Major Mitchells because of where they live. My grandad had a sulphur crested cockatoo that lived longer than he did, but they’re very common as pets. And highly destructive.

    • dave chamberlin says:

      I was raised taking care of a horses and a burro. The burro was an incredibly smart animal compared to the horses and lived twice as long. The mule combines the longevity of the burro, or donkey, the intelligence of the donkey, and the strength of the horse. The increased intelligence of the burro gave him far more personality and he was much beloved by my family. I can see how the mule was greatly favored as a work animal not just because of their size, strength, and ability to work hard up to age 50, but their higher intelligence made them a far more useful work animal for complex chores. If you loved a burro they would love you back, almost like a dog. I never got that feeling from our horses, although other people have. Here is a weird factoid coming from mule expert and mule promoter for the American public, the father of our country George Washington. While president George was gifted two excellent mules from the country of Spain. He put them to work on his Virginia farm and found them so useful that he was quite instrumental in promoting them to their important place in pre-industrial agriculture. I don’t consider that so interesting but the following information is. Mules were always the result of a male donkey and a female horse. A female donkey could deliver a foal from a male horse but it was a more difficult delivery. While the mule was of great use in agriculture the hinny, the result of a male horse and female donkey and was considered by George Washington and other people of the time, who knew what they were talking about, to be a useless work animal. It was smaller, weaker, uncooperative, and very mean. It would seem that crosses from highly diverse animals vary quite a bit depending on whom is the father and whom is the mother. Possibly our neanderthal fraction has all come from males and none of it from females because of multiple disadvantages from the opposite cross. I have absolutely no proof of this just food for thought.

      • reiner Tor says:

        Possibly our neanderthal fraction has all come from males and none of it from females because of multiple disadvantages from the opposite cross.

        I disagree. If it comes from males, that’s only because Neanderthal males might have been more attractive to females (stronger, more masculine) than Cro-Magnon males to Neanderthal females. However, given the dynamic of contact, Cro-Magnons were quickly replacing Neanderthals (I saw recent findings propose it took place quicker than previously assumed), which means they probably were dominant and thus protected their own women while conquering Neanderthal females, a few of whom could survive with the mixed offspring, who thenceforth belonged to the Cro-Magnon tribe.

      • reiner Tor says:

        Neanderthals also had longer pregnancies and probably had bigger babies, so hybrid children would be easier delivered by Neanderthal women than by Cro-Magnon women. I’m quite sure most or all Neanderthal admixture was that of Cro-Magnon males and Neanderthal females.

      • dave chamberlin says:

        I have no idea who mated with whom so you could be right reiner. I didn’t mean to argue that we only have male or female neanderthal ancestors but that at least in the case of mules there is a large difference in the outcome depending on the sex of the parent so it could be true with us as well. Please note that we only have proof that we mated with male neanderthals and none that we mated with female neanderthals. But this doesn’t mean much because there could be a disadvantage with neanderthal mitochondria so that it is no longer with us. I see the logic in your argument and would include to it that when one population replaces another it is more likely that males from the dominant population take females from the population it is replacing.

      • IC says:

        @reiner Tor
        Drop that kind of imaginary argument. Just look at today of black men/white women pair. It can go either way. Only way you can protect your women is turn your faith into Islam and cover your women up. Or lock them up.

        This makes yourself feeling good argument always flawed. In sciene, wishful thinking is always clue of non-scientific mind.

        You are very likely not a scientits. Am I right?

      • engleberg says:

        I’m no icy scientits either, but when I looked at those internet pictures of fore-and-aft brain nerve connections for males, port-starboard females, I thought of long-headed Neandertal skulls poking way out in back and wondered if male-descended moderns kept some connections. Looking Neanderthal is more copacetic for guys.

      • reiner Tor says:

        Just look at today of black men/white women pair.

        Because whites are rapidly displacing blacks right now. This is called institutional racism.

        Actually, no. Whites are not rapidly displacing blacks. Since the highest ranking leader of the realm is actually black, there’s no reason to assume whites are socially dominant over blacks. They aren’t.

        It’s also obvious Cro-Magnons had no political correctness, and that relations between neighboring Cro-Magnon and Neanderthal tribes were more often than not openly hostile. I’d be surprised if Cro-Magnon parents were happy to see their daughter marry into the tribe of their enemies.

        Also apparently humans are natural racists: the first things we notice about another human are its sex (male or female) and race. A person of different race usually elicits some kind of fear response in the brain.

        I’d also be happy to investigate what makes you think that I’d feel more content having Neanderthal maternal rather than paternal ancestors. I mean, seriously: if Neanderthals raped Cro-Magnons, then that’s just a case of one set of my ancestors raping another set of my ancestors, as opposed the second set raping the first set… It reminds of the joke about communism (officially called socialism back then) that in capitalism man is being exploited by man, whereas in socialism it’s the exact opposite.

        And finally there’s still the argument that Neanderthal mothers were pregnant for eleven months. A hybrid child needed maybe ten months pregnancy – very difficult or impossible for the Cro-Magnon woman to bear.

        But I’m open to arguments since it really doesn’t matter to me. All I know is that great-great-great-…-great-grandpa screwed great-great-great-…-great-grandma. I do care which was Cro-Magnon and which Neanderthal, because I do care about my ancestors. But I’m mostly interested in reality.

      • reiner Tor says:

        @IC: My longer answer is probably waiting moderation.

      • reiner Tor says:

        I don’t know where I read that Neanderthals were pregnant for eleven months. Probably it was roughly the ordinary nine months. However, I found this, which states that “the birth canal of this woman was wider than that of a Homo sapiens mother, but the head of the Neanderthal newborn was somewhat longer than that of a human newborn because of its relatively robust face. This meant that for the Neanderthals, the birth was probably about as difficult as it is for our own race.” However, this also means that for a Neanderthal mother it most have been easier to bear a hybrid than for a Cro-Magnon mother, because hybrid babies were probably somewhat smaller than Neanderthal babies and a little bit larger than Cro-Magnon babies.

        This is my answer to Dave Chamberlin, that basically a Cro-Magnons to Neanderthals are like donkeys to horses: the former were smaller than the latter. In other words, hybrids born to Neanderthal mothers are like mules, whereas hybrids born to Cro-Magnon mothers are like hinnies.

      • Simon in London says:

        ” It would seem that crosses from highly diverse animals vary quite a bit depending on whom is the father and whom is the mother”

        I remember seeing IQ data which showed black father/white mother offspring as having much higher IQ than black mother/white father. This seemed odd at the time since AFAIK black mother/white father pairings are likely to be more stable and have higher SES.

    • melendwyr says:

      “why do I get hay fever, then?”
      Increased risk of allergies is associated with strong immune systems in the absence of real immunological threats.

  17. pdimov says:

    I can’t help but wonder whether it is a coincidence that this post appeared shortly after

    http://www.macroevolution.net/human-origins.html#.UrOPLWfxuRE

    got some news coverage. I also wonder whether we should believe a word of the above.

    • gcochran9 says:

      Not one word. This guy has worms in his brain. But he raises an interesting question: what should we think of men who come up with truly, deeply crazy stuff on their own, compared to people who go along with society-wide stuff that is just as crazy?

      • TWS says:

        Truly weird that explains my aversion to cleanliness as a child

      • j3morecharacters says:

        The genome of the pig (Sus scrofa) comprises 18 autosomes, with X and Y sex chromosomes. The genome size is similar to that of human at around 2.7Gb. There is extensive homology between the pig genome and the human genome. The pig is the best model we have to understand human health problems such as obesity and cardiovascular disease. McCarthy’s idea may sound crazy, but then this is a crazy world.

      • misdreavus says:

        “There is extensive homology between the pig genome and the human genome.”

        yes, and also between the mouse genome and the human genome, to the point where nearly 95% of mouse genes or so have homologous equivalents in human beings. So what? Just about none of the chromosomes will match up during meiosis.

    • dave chamberlin says:

      Fascinating link which begs two possible answers.
      1)This is the artful work of a troll
      2)People are with few exceptions are amazingly ignorant and stupid

      We are a pig chimpanzee hybrid, I can come up with far better bullshit than that. I noticed that every comment thrown into this article was very receptive to this retarded idea which leads me to believe it is well done troll work. I love the inclusion of two pictures of our expert holding his blond and dark haired daughters, as if this variation is nearly the same thing as the love child of a chimp and a pig. Here goes my news story.

      Escapees from Chinese Genius Pig Farm Raising Hell
      It started as an experiment, but it ended as a disaster. Scientists using cloned pigs with an added chromosome that included many human genes encouraging brain development were making great strides in not only understanding the underpinnings of human intelligence but in raising pigs that with their agile snouts could solve complex puzzles that made them the equivalent of seven year old children. Well twenty of them escaped and are proving as of yet impossible to catch.
      “There are thousands of them now up those hills,” said one Loo Wan Chan. “and they know exactly when to come down and raid our farm fields.”

      If you want to successfully sell bullshit the key isn’t to be sensible (sad but true) but to sell bullshit people want to believe. Nobody wants to believe we are the hybrid of a pig and chimpanzee. But lots of people want to believe we shouldn’t be messing around with human intelligence and if we do so bad things will happen.

      “We don’t dare go up in those hills and hunt them,” added Mr Chan. “They dig holes and hide them so that we will fall into them and break our legs. People who go up there don’t come back. The army is up there trying to exterminate them but they hide from large groups of armed men but ambush small groups.”

    • Toad says:

      Has anyone ever done experiments trying cross-species lab fertilization? It be possible to prove experimentally.

    • Toad says:

      It says that as hybrids we have depressed fertility. That would mandate a ‘K’ breeding strategy as a species.

  18. tiajuanais mariais says:

    Herr Cochran, do you think we have the technology now to make a 64 chromosome none sterile mule? Would it be a new species or just a mule.

  19. Cattle Guard says:

    Wasn’t there an Irish-Aborigine guy who ran the 100 meters under 10 seconds? First generation Bushmen-Aborigines might be able to set some world records, have great careers in American football or rugby…

    • anon890 says:

      Patrick Johnson (born 26 September 1972, Cairns, Queensland, Australia) is an Australian athlete. He is the current Oceanian and Australian record holder in the 100 metres with a time of 9.93 seconds, achieved in Mito, Japan, on 5 May 2003. With that time he became the first person not of West African ancestry to break the 10-second barrier.[1] The time has made him the 17th fastest man in history at the time and 38th man to crack the 10-second barrier, and currently the oldest (30 years, 221 days) athlete to crack 10 seconds. [2] He was regarded as the fastest man of non-African descent before Christophe Lemaitre ran 9.92 seconds in French National Championships in Albi on 29 July 2011.[3]

      Johnson’s mother was an Indigenous Australian and his father is Irish.[2][3]

  20. Since recessive deleterious mutations are typically rare, the potential adverse health consequences of notably altering race-specific genetic correlation structures outweigh the possible race-mixing benefits related to decreasing the likelihood of obtaining identical copies of recessive deleterious mutations from parents belonging to different races.

    Sometimes people will try to claim that if different races breed, they are—through hybrid vigor—somehow superior. But hybrid vigor only produces more viable offspring that have increased mutational loading. The offspring of a mixed-race couple then still depends on the quality of the genes of the parents. Let’s take two examples. In the first, an all-star Black running back for a football team marries an average White women rather than another Black. Chances are their children will be less athletic than dad was, and may have fewer chances for success as an athlete. The smart thing would be for an athlete to marry a similar type of athlete for the children to follow in their footsteps as athletes.

    To address the question whether there is an IQ variation due to race mixing, ideally one would mix races with the same cognitive abilities, but races differ in their cognitive abilities. Since a substantial proportion of the variance in IQ is accounted for by additive genetics, when races of differing cognitive abilities are mixed, the mixed offspring tend to have intermediate scores on cognitive abilities. Therefore, any possible deleterious effects of race mixing on IQ are masked by the additive effects of the genes. Further, some of the genes behind IQ are non-additive, and the contributions of the non-additive genes also mask any possible deleterious effects of race mixing on IQ. The question whether there is an IQ decrease due to race mixing compared to the IQ of the offspring of same-race individuals—when the parental disparity in cognitive abilities is controlled for—will likely be answered in the future when better data are available.

    Another similar example would be for a successful White academic marrying a Black colleague with a position obtained through affirmative action, not intelligence. The children, on average, would fall somewhere between them in intelligence. So who benefits? The children will probably be smarter than the Black parent but less intelligent than the White parent. The smart thing for any parent is to try and marry someone who will compliment them and improve the genetic quality of their children. That is, if I really care about having intelligent children, I should try and marry a woman who is more intelligent than I am. Actually, since most men object to marrying women that are smarter than they are, it leaves eugenic minded males with a real opportunity. There is a surplus of intelligent, successful, and single females in the West because of this imbalance in mate selection.

    • reiner Tor says:

      There is a surplus of intelligent, successful, and single females in the West because of this imbalance in mate selection.

      Yeah, but they also want males who in turn are even more intelligent and successful than they themselves are. Nearly half of female CEOs are unmarried, but those that are married, are mostly married to male executives with on average still higher incomes.

    • Richard Sharpe says:

      Since recessive deleterious mutations are typically rare

      It seems counter intuitive to me that they would be rarer than dominant deleterious mutations.

    • Toad says:

      marry a woman who is more intelligent than I am

      On the other hand, that would require smart women to start to marry less intelligent men and have less intelligent children.

      Women are naturally less intelligent than men, and if one is abnormally more-intelligent, it could be the result of a defect, like a glandular imbalance of too much male hormones.

  21. Neil craig says:

    Jewish/Parsee perhaps since both appear to have recent but separate evolutionary history towards increased IQ.

  22. There has been an experiment along those lines in Sout Africa. The Xhosa have some San admixture. Their language contains click sounds and Mandela seemed look a little be Bushman, at least compared to Buthelezi.

  23. “Wasn’t there an Irish-Aborigine guy who ran the 100 meters under 10 seconds? First generation Bushmen-Aborigines might be able to set some world records, have great careers in American football or rugby…”

    Might be too small for the NFL or Rugby.

    Would like to see a San or Abo cross with an Eskimo for the next Bobby Orr.

    • Cattle Guard says:

      True. Send the big ones to the NFL to play running back or linebacker, smaller ones to win your country gold medals in Olympic sports that have weight classes. And make a whole team of Bobby Orrs (with a Bob Probert or two thrown in for good measure) on the side.

  24. The fourth doorman of the apocalypse says:
  25. TWS says:

    Serious question – There are fertile crosses between the one and two humped camels with similar results to mules regarding the preference for sex of parents. They seem to exhibit superior traits across the board as a domestic animals. However, second and especially third generations bred from these crosses do not.

    Why? Why don’t the desired traits fix? Why do they regress to less than the abilities of the original parent strains muchless the original crosses?

  26. tommy says:

    Years ago, I recall reading one old study that suggested the offspring of whites and Sioux Indians (or perhaps it was another Plains Indian tribe?) tended to be a bit taller than either parent. The authors suggested that height was mediated by somewhat different genes in each parent population.

  27. {insert boilerplate joke about future overlords}

  28. The fourth doorman of the apocalypse says:

    Not only is there an achievement gap, there is an infant mortality gap:

    http://www.sciencedaily.com/releases/2013/12/131219162942.htm

  29. Gottlieb says:

    There not seems to work for mulattos. For hybrid vigor happens I that is necessary to have some similarity to features that are super maximized believe. For example, Asian and white, or white and Ashkenazi. Ie, it is necessary that in the case of intelligence, that genetically distinct populations are on the same starting point, at the same level or at similar levels.
    You can not say that Eurasians are a mistake because of the crossings in Central Asia, because the Turks appear as a component within the umbrella” Caucasoid”. However, it is necessary to make an analysis of Eurasian populations (neglecting the Central Asians) in the USA, in Singapore, in short, in all environments where this particular type of crossing has happened. Brazil should also have many restrictions, because the intersections between Asians and non-Asians has given Brazilian with the most diverse mixtures.

    The hybrid vigor does not seem to relate entirely to the phenomenon of genius , since at least according to the biographical evidence of most known geniuses of the Western world , physical strength or health were not their strengths .
    However , it seems that the most notorious geniuses of European history , emerged in the Central European region , to England , which due to its insular nature , seems to have developed some small genetic difference from the mainland populations . Many Russian geniuses , beyond the Ashkenazi Jews , seem to indicate a relationship between hybrid vigor and genius , but very specific and weak relationship , since these regions are known to exhibit different racial sub pressure phenotypes , Russia under pressure in specific populations mixed Eurasian around Central Europe with a mixture of several Caucasian phenotypes such as the Nordic north , to downtown Alpine and Mediterranean south . Beethoven did not look like a typical German , more on Joseph Ratzinger .
    Maybe there are two types of hybrid vigor , physical and mental , the first of which relates to fitness course while the second relates both to the increasing intelligence of the population , as the sporadic emergence of geniuses .

  30. Pingback: Benefits of Hybrid Vigor Overstated | Occam's Razor

  31. Anonymous says:

    Half Jewish / Europeans have the highest IQ’s of any group (or so I read somewhere).

    There is a confounding factor. Higher IQ’s correlate with the rejection of traditional values. Ergo, higher IQ’s are more likely to outbreed against traditional mores. Further, the highest IQ jewish men will outbreed for the shiksas.

    http://en.wikipedia.org/wiki/Felix_Mendelssohn had a wealthy Jewish father / beautiful Christian mother. Judah Benjamin did the same.

    Mendelssohn is an outlier because his sister shared his talent. She was arguably the greatest female composer (which really isn’t saying much). One flag for Galtonian eminence in a family line is that even the women hilariously over-achieve. When you have a brother/sister/father trifecta of talent, it should notable because it is statistically nigh impossible.

    • Janon says:

      Both of Felix Mendelssohn’s parents were ethnically Jewish. His mother was born Lea Salomon and was a granddaughter of David Itzig, Frederick II’s court Jew. Felix Mendelssohn’s wife, Cecile Jeanrenaud, was not Jewish. One of their sons was a chemist who co-founded the chemical company AGFA.

  32. Tomás says:

    “I’ve seen a study that observed a moderate IQ advantage in Japanese-European kids in Hawaii, something like a quarter of a standard deviation, but I don’t think it’s been replicated, and that’s not enough change to get excited about in any event.”

    Of course. But there is more than that.

    Given the tone of many comments, I thought it was necessary to remind people that IQ, per se, is of no value. IQ is important as long as it is adaptive to a given environment. It’s extremely important to understand that, at the end of the day, it is adaption to the environment, not IQ as such, the most important concept. At the end of the day, who gets more inclusive fitness is the winner.

    Cognitive elitists are always forgetting about that. The great Satoshi Kanazawa has oftenly reminded us, again and again, the downsides of a extremely high IQ in our current environment. While during centuries the most intelligent people seemed to reproduce more (“A Farewell to Alms”, and also other sources) for the last two hundred years it’s been the other way around.

    It is still unclear why, but the cognitive elite simply doesn’t reproduce itself anymore. They live unhappier lifes, they sleep less, they show a tendency for all kind of novel deleterious behaviors (memes) and, even more importantly, they simply don’t reproduce themselves.

    One can theorize that a cognitive elite like this one would be anyway increasing their inclusive fitness via the benefits bestowed upon their extended family of millions of individuals (a “Salterite mechanism”). Maybe that’s been the case for the last two centuries. However, given the current cultural developments, with the cognitive elitists pushing for a transnational rootless group of deracinated mixed uber-individualists, and given the predatory behaviour shown by this elite in the recent years, it is not clear if it is going to be the case anymore. Assuming the theory was right in the first place.

    Bottom line: what is needed and desirable is a organic cognitive elite culturally oriented to the well-being of its extended family, strongly identified with it, not a rootless group of individualist high-IQ mongrelized decadents.

    • kn83 says:

      Satoshi Kanazawa’s claims doesn’t seem to apply for people that aren’t W.E.I.R.D (NW Euro descent). Neither does his Savannah Hypotheses in general. Its based on the mistaken assumption that humans stopped significantly evolving after agriculture and that any behavior not adapted to hunter-gathering is “novel”. It just falls apart when you look at non-western and non-white populations. There doesn’t seem to be any strong link between high-iq and far-leftism for example. Research has been shown that Iq by itself has no effect on fertility (though higher education for women does negatively effect their fertility since they are spending most of their fertile years studying while holding off marriage). Billionares and Fortune 500 CEOs tend to have IQs in the top 1%-2% range and higher fertility rates than most non-african nations today. The only thing that Kanazawa seems to be right about Iq is that smarter people do seem to be less religious on average in any society.

      Iq, by itself doesn’t have much of an effect on personality or character. The mal-adaptive traits associated with the western elite are actually quite inherent to NW Euros in general, cause by their unique evolutionary history.

  33. Tomás says:

    There is another idea that I find important to clarify and that has been lurking in my mind for a while after reading the rest of the comments.

    Inbreeding depression, outbreeding depression and heterosis, all three, operate of the level of traits. It’s not some kind of “general state” of an organism, but a relative increase or decrease in fitness in some particular trait. The three processes are highly independent and the three of them can appear at once, at the same time.

    Let’s take the famous example of the mule. The mule enjoys increased strength and longevity. That’s hybrid vigor *on those traits*. On the other hand, it clearly suffers of outbreeding depression on its reproductive function. In fact, the backslash is so huge that the mule is a biological dead-end.

    Low-brow thought: if the mule could choose, it will surely choose not to have so much hybrid vigor… and so much hybrid decadence (outbreeding depression).

    Another famous case is the reintroduction of the oryx in some areas of the arabian peninsula. Its reintroduction was made with just a bunch of individuals from different races. Later on it was detected that the oryx was suffering from consanguinity *and* hybrid decadence. Both at the same time. A very small founder population gathered from too distant sources.

    How is it possible to suffer all the effects at once? Because the inner mechanisms of each one are different. They don’t compensate, at the very least, not always and not for every trait.

    Under the label of “outbreeding depression” we lump together two different processes: the loss of local adaptions (which is very important in the first generations of hybrids) and the breakdown of supergenes (complexes of co-adapted genes that regulate some trait in common). The second one is not so spectacular in the first generation but is more insidious, because it increases from the second generation onwards as long as the hybrids keep hybridating between them.

    Those gene complexes are very important, for example, in the functioning of the immune system. It’s not any wonder, then, that one of the systems more weakened in the subsequent generations of hybrids is the immune one.

    It is also very important to keep in mind that these three categories are highly dependent on the species, the population structure, the previous mating history, etc. It’s a extremely complex area. There are species (many of them, insects) that practice a very high level of inbreeding without suffering of inbreeding depression whatsoever.

    If a population faced with inbreeding survives to its negative consequences, in the long term it will flourish again, because inbreeding depression tends to decrease in time. The deleterious alleles are filtered out (high mortality) and there appear new mutations too.

    A high level of inbreeding (in a big population, so it might not be valid to label it as “inbreeding” in the first place) is a essential feature of the process of speciation.

    On the other hand, unrelated to these depressions and to heterosis, there is the vital topic of parental kinship, as a particular instance of kin-based altruism.

    Considering all the above, it’s clear that in any given species we will have some forces pushing against inbreeding and some others pushing against outbreeding. The relative strength of those forces change for each organism.

    For birds there were many experiments (in the 70’s) that showed that they prefered as mates those individuals somewhat different from those which they were raised with, but not too different. They prefered something like a ‘distant cousin’, so to speak.

    Curiously enough, it seems that, for icelanders, their fertility gets boosted when mating with third and fourth grade cousins.

    http://www.sciencemag.org/content/319/5864/813.full

    To be true, the dangers of inbreeding are culturally manageable. In huge areas of the world traditional cultures favor some types of cousin marriages, with complex systems to avoid getting too much consanguinity, because it keeps resources within the family and creates a big extended clan of highly-related individuals. Africa, the Middle-East, Pakistan, India, medieval Ireland and Scotland, the Caucasian area… In many environments it seems that the downsides of a relatively higher inbreeding are positively compensated by its benefits. There are places and times where individualism and extreme outbreeding don’t seem to work exactly well.

    • Greying Wanderer says:

      Interesting post.

      “To be true, the dangers of inbreeding are culturally manageable. In huge areas of the world traditional cultures favor some types of cousin marriages, with complex systems to avoid getting too much consanguinity”

      Wouldn’t child mortality rates be relevant to this? If an in-breeding population in the past had an average of twelve children per couple with only the two healthiest surviving then wouldn’t the end result be different to the same population having an average of two children and both surviving due to modern medicine (or having twelve and all twelve surviving.)

  34. Tomás says:

    Just for the record: the best account of all these questions that I’ve found so far is the classic “Mate Choice”, edited by Patrick Bateson, the ethology professor from Cambridge. It’s a book of 1983, but it is a gem. 21 articles from leading scientists, including Bateson, who personally conducted some of the most interesting experiments (with birds) related to this area. You can find it in Google Books, but not all the pages are shown.

  35. Tomás says:

    A wealth of information coming from Edwin Schmidt’s great blog:

    “Active Inbreeding in a Cichlid Fish and Its Adaptive Significance”, Timo Thünken et al.; 2007.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/active-inbreeding-in-cichlid-fish-and.html
    http://www.sciencedirect.com/science/article/pii/S0960982206025711

    “The genetic interpretation of inbreeding depression and outbreeding depression”. Michael Lynch; 1991.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/the-genetic-interpretation-of.html
    http://the%20genetic%20interpretation%20of%20inbreeding%20depression%20and%20outbreeding%20depression/

    “Simultaneous inbreeding and outbreeding depression in reintroduced Arabian oryx”, T C Marshall and J A Spalton; August 2000, “Animal Conservation”.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/simultaneous-inbreeding-and-outbreeding.html

    “Modeling Factors Affecting the Severity of Outbreeding Depression”, Suzanne Edmands and Charles C Tmmerman; June 2003, “Conservation Biology”.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/modeling-factors-affecting-severity-of.html

    “Inbreeding and outbreeding depression in Caenorhabditis Nematodes”, Elie S Dolgin et al.; 2007.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/inbreeding-and-outbreeding-depression.html
    http://www.researchgate.net/publication/6293240_Inbreeding_and_outbreeding_depression_in_Caenorhabditis_nematodes/file/79e4150f6bef69a11f.pdf

    “Increased Infectious Disease Susceptibility Resulting from Outbreeding Depression”, Tony L Goldberg et al.; April 2005, “Conservation Biology”
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/increased-infectious-disease.html

    “Hybridization rapidly reduces fitness of a native trout in the wild”, Clint C Muhlfeld et al.; 2009.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/hybridization-rapidly-reduces-fitness.html
    http://rsbl.royalsocietypublishing.org/content/5/3/328.full

    “Outbreeding depression, but no inbreeding depression in haplodiploid ambrosia beetles with regular sibling mating”, Katharina Peer and Michael Taborsky; 2005
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/outbreeding-depression-but-no.html
    http://www.researchgate.net/publication/7929635_Outbreeding_depression_but_no_inbreeding_depression_in_haplodiploid_Ambrosia_beetles_with_regular_sibling_mating/file/60b7d5140e917302c3.pdf

    “Predicting the Probability of Outbreeding Depression”, Richard Frankham et al.; 2011.
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/predicting-probability-of-outbreeding.html
    http://www.vortex9.org/reprints/FrankhamConsBiol2011.pdf

    “Maximum for partial reproductive compatibility”
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/maximum-for-partial-reproductive.html
    Source: “Does parental divergence predict reproductive compatibility”; 2002
    http://www.researchgate.net/publication/223003075_Does_parental_divergence_predict_reproductive_compatibility/file/79e41511133590ef1e.pdf

    “Between a rock and a hard place: evaluating the relative risks of inbreeding and outbreeding for conservation and management”, Suzanne Edmands; 2007
    http://meinnaturwissenschaftsblog.blogspot.com.es/2013/11/between-rock-and-hard-place-evaluating.html
    http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2006.03148.x/full

    And finally, this one, extremely important. The fitness optimum in a human population (icelanders) seems to be when mating with cousins in the third and fourth grades (available after a free registration):

    “An Association Between the Kinship and Fertility of Human Couples”
    http://www.sciencemag.org/content/319/5864/813.full

    Technical comment on the previous paper:
    http://www.sciencemag.org/content/322/5908/1634.2.full.pdf

  36. Anonymous says:

    mules appear to be “smarter” than either parent species; could we uncover the IQ gene(s) if dominance is the mechanism that underlies mule IQ? that is to figure out which gene(s) actually masks/covers/supressess the complementary recessive gene(s) if and only if it(they) is/are present?…

    • melendwyr says:

      No, not really.
      A cross that humans persist in creating has to have some major benefits if they’re going to keep producing it. Mules happen to have some advantages over their parent species from the point of view of someone seeking a particular type of work animal. If they were worse off on the desired characteristics, humanity wouldn’t bother breeding them very often and we probably wouldn’t be discussing them now.
      Even ignoring their chromosomal sterility, it’s worth pointing out that mules happen to be well-suited for a very unusual niche – interacting with humans. In a wild environment, mules would likely be less well adapted than either of their ancestors. If their special traits were valuable in that niche, they would already exist in donkeys and horses.

  37. stareintotheabyss says:

    You aren’t having enough fun with this one. Breeding of humans should be strategic (like with dogs).

    1)
    Hard working but schizoid asians
    + lazy lively Italians = balances out the negative traits
    http://anthrocivitas.net/forum/showthread.php?p=202321

    2)
    Brilliant + lacking intellectual discipline + Aski jews
    + scrupulously uncorrupt Norweigans =

    Jake Gylanhall

    3)
    Cold German brains & discipline
    + spirited africans

    Someone in there is an ideal breed.

  38. Pentagon says:

    Nations with high levels of halfbreeding are fails in general, socially chaotic.
    The mule might be strong to serve, but its system lacks the strength to reproduce.

  39. Fabio says:

    “I’ve seen a study that observed a moderate IQ advantage in Japanese-European kids in Hawaii, something like a quarter of a standard deviation, but I don’t think it’s been replicated, and that’s not enough change to get excited about in any event.”

    Interesting. What’s the name of the study?

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