Benefits of Hybrid Vigor Overstated

Gregory Cochran has an interesting post up about the possible advantages of hybid vigor (heterosis), i.e. the possible advantages of offspring from two genetically dissimilar parents.

I think the advantages of hybrid vigor might be overstated.  While hybrids could possibly introduce beneficial genes, what is more important than producing hybrids is selection pressure for  favorable genes.  Hybrids might at one point been a mechanism to introduce adaptive traits, but in the near future such traits could be introduced via genetic engineering and then artificially selected for, as with domesticated animals or plants.

Cochran is right that whatever advantages hybrid vigor might bring are basically “a first-generation effect.”   One sees this with canine mutts, where after mutts interbreed for multiple generations, especially in the wild, mutts will often develop pariah-like characteristics, losing their traits of domestication.  In short, there is no (artificial) selection pressure on mutts for (beneficial) domesticated traits.

Cochran also states that hybrids among more genetically distant populations could possibly produce more beneficial traits, but there are plenty of counterexamples to this.

For instance, the genetic distance between Europeans and Amerindians is significant, but mestizos do not in anyway seem remarkable.  Other than the donkey show and taco, mestizos haven’t contributed much to humanity.  Mestizos are fairly mediocre both academically and athletically, as evidenced both by Mexico’s poor academic performance and low medal count in the Olympics, and mestizos don’t really seem to excel at much, other than the recent honor of being the most obese people on the planet.

Mestizos are a walking and breathing counterexample to the benefits of hybrid vigor.

Further Reading:

What Race Are Hispanics?”

95% of White Americans Have No African Ancestry

Eccles & Mount:  “Cross-breed Dogs Have More Health Problems than Purebred Dogs”  (For “Pariah Dogs,” see entry here.)

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15 thoughts on “Benefits of Hybrid Vigor Overstated

  1. the genetic distance between Europeans and Amerindians is significant, but mestizos do not in anyway seem remarkable.

    You need to distinguish between mestizos and indios. Mestizos are inferior to whites, but they are a lot closer to the white norm than the indio norm.

  2. You’re right about it being a first-generation thing. A stable generations-old interbreeding population of hybrids is at no particular advantage.

    Second, hybrid vigor is primarily about suppressing deleterious recessive traits brought out by inbreeding. It is an important but fairly lomited effect. It does not predict that hybrids will be all around superior, only that they will be less susceptible to genetic ailments. So the Asian/Jewish kid may not necessaroly be better at school or sports than his parents, but he will be less likely to suffer from Tay-Sachs, Krohn’s disease or Raynaud’s syndrome.

    Third, you’re right about selection pressures. Look at the kids that Cathedralarchs are producing – WASP/Jewish and/or Asian hybrids, with some lace curtain ethnic-American and foreign PhD thrown in here and there. We don’t like the Cathedral but these are some beautiful high IQ kids who will be at least passable at sports. Now look at Dominicans. Also hybrid, ugly, bad at school, bad at sports (unless you count baseball as a “sport”).

    Hybridity can have some useful effects, but talking about the benefits of in- or out-breeding is pretty beside the point if we don’t specify what selection pressures do (or should) apply.

    • You are the dumbest retard I have ever encountered online. You can’t find any examples of outstanding Meztizo because you deaf, dumb, and blind. Get in the ring with me and I will show you some hybrid vigor over and over.

  3. 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.

    Some info, truly good:

    “Strands of Undesirable DNA Roam With Buffalo”, The New York TImes. Easy and informative.
    http://www.nytimes.com/2007/01/09/science/09bison.html?n=Top/News/Science/Topics/Animals&_r=1&pagewanted=print

    “Feeble roar of the hybrid lions”, BBC News. First, outbreeding depression. Then, inbreeding one.
    http://newsvote.bbc.co.uk/mpapps/pagetools/print/news.bbc.co.uk/2/hi/south_asia/4101049.stm

    A wealth of info coming from Edwin Schmidt’s 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

  4. Hybrid vigor does not apply to the second or third generations. So modern mestizos should not be better than the sum of the parts. Guys like Jim Thorpe or perhaps Yvonne Goolagong might be better examples (I’d have to check when the mixture occurred).

    That’s why a mixture that proved better than the parent stocks would actually require the parent stocks to be maintained in their pure forms. Also, some mixtures work better with the father from population A and mother from pop B. Forex mules work best with a donkey father and horse mother. Also the quality of the parent stock matters.

    The early metis who pushed west for the French and English were a far cry from the metizos who farmed corn for the Spanish.

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  9. Living in a bad enviroment can contribute to negative hybrid vigor. The positive results of hybrid vigor will not show if an individual with excellent characteristics lives under poor conditionts, but now and days many African Americans are having academic success due to the oportunitys they were given in the U.S.A compared to those of in Africa. Every man is created equaly, and if each ethnicity is given the equal chance to thrive in academics they will succeed. I attend school in America and I can see that foreigners offten performe better than natives in academics when given the chance, but the American youth only seems to be concerned with the number of facebook “likes” they receive and what they wanna “blow on” after skooool. They will even pick on you because you’re not wearing Jordan’s, apearantly they don’t like that…I wonder what kind of hybrid vigor they come from?

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