Hybrid vigor (heterosis) does not seem to apply to humans as we are already very heterozygous, at 0.776 [
http://mbe.oxfordjournals.org/content/14/7/707.full.pdf] Compared to dogs for example at 0.401. [
http://www.eebweb.arizona.edu/Courses/Ecol406R_506R/Garcia-Moreno1996-Wolf.pdf]
Although some argue that race mixing "averages out" traits and since average faces are considered more attractive [
http://cs.brown.edu/courses/cs143/2009/lecture13.pdf] then mixed race offspring are more attractive.
However this is fallacious as it assumes we are designed for perfect symmetry, when in fact the magnitude of asymmetry is the correct measurement and this random component fulctuates, also called "fluctuating asymmetry" - so more honestly a lower level of asymmetry correlates with increased attractiveness, not symmetry.
http://beheco.oxfordjournals.org/content/15/5/864.abstract But does increased heterozygosity cause lower asymmetry? A meta analysis of 118 datasets in 14 studies showed a very weak inverse correlation between the two, showing that increased heterozygosity has no beneficial effect on symmetry or asymmetry
http://www.nature.com/hdy/journal/v83/n2/full/6885550a.html One study on the craniofacial morphology in White-Amerindian mixed race individuals found that over half of the 52 shape variables deviated from the mathematical average completely shattering the above argument.
http://majorityrights.com/images/uploads/spanish.indian.pdf The neurotransmitter oxytocin "makes people more co-operative, benevolent, loyal, generous and trusting of others. It is involved in the parent-child bond - new mothers and fathers have raised levels of oxytocin. Production also increases when people hug and when they have sex and, recent research suggests, when they receive psychological warmth." However, oxytocin has been alleged to "foster racism."
http://www.guardian.co.uk/technology/2011/jan/30/bright-ideas-oxytocin-hormone-racism The study found that "intergroup bias that fuels prejudice, xenophobia, and intergroup violence… Which maybe modulated by brain oxytocin." This suggests that the instinctual desire to pursue the interests of one's own ethnic group to further ensure the existence of one's people is linked to racial bias, coinciding with the observation that diversity is a weakness, not a strength.
http://www.pnas.org/content/early/2011/01/06/1015316108 One study found that during the menstrual cycle when women have a higher likeihood of conception, racial bias is increased, especially when the likeihood of sexual intercourse was increased; "increased conception risk was positively associated with several measures of race bias. This association was particularly strong when perceived vulnerability to sexual coercion was high."
>Although egalitarians suggest that only a racist would consider race when it comes to reproduction and mate choice, this study observed a general, innate tendency to prefer one's own race especially when most likely to be impregnated.http://www.cdnresearch.net/pubs/private/racebias.pdf Race Is A Social Construct?
The Immune System: How Important Is Race?
>"If Nick Glasgow were white, he would have a nearly 90 percent chance of finding a matching bone marrow donor who could cure his leukemia." The reason that mixed-heritage patients are so hard to match can be found in the immune system. Different races have developed certain proteins, or markers, that are part of the body's natural defenses. These markers help the immune system determine which cells are foreign and should be rejected.
Are cells racist?
A match between two people who share more genetically in common significantly reduces the risk of the donor and recipient cells attacking each other. (READ: cells from people of two different races will attack and fight each other as though they are a virus)
The more people of different backgrounds who produce offspring = the more types that are harder to match.
Multiracial patients have uncommon profiles and since there can be many possible racial and ethnic combinations in multiracial societies, finding a match can still be extremely difficult.
http://m.phys.org/_news162659550.html