Update: Over at Genetics and Health:
Last month, 12-year-old Bobby Stephens, Jr. died after football practice in Florida. This week, his family learned that he carried genes for both Hemoglobin S and Hemoglobin E. There have only been 27 documented cases world-wide of people who've died as a result of the combination of both of these two genetic mutations.
...
Hemoglobin S. This the predominant hemoglobin in people with sickle cell disease.
...
Hemoglobin E trait is benign. Hemoglobin E is extremely common in S.E. Asia and in some areas equals hemoglobin A in frequency.
...
Bobby had a higher probability of inheriting these specific genetic mutation from his parents because his mother is Thai and his father African-American.
Interesting, though let's keep a sense of perspective, 27 individuals does not a terror make.
End Update
Over at Sepia Mutiny there is post about cute little brown girl who needs a bone marrow transplant because of leukemia. This is a case where correlation structure and the details of genomic variation matter quite a bit. You see, variation on the HLA cluster of genes determines your immunological profile which dictates whether you are a "match" with potential donors. There are many HLA genes, or loci, within the genome. "Classically" there are nine. On top of this, the genes are extremely polymorphic, in fact, the HLA loci are amongst the most polymorphic prominent regions of our genome. The reason is simple: The Red Queen effect. Diversity is protective insofar as a very common immunological profile is a perfect host for a proliferating pathogen. In contrast, rare variants encode for strategies which pathogens have not developed a counter-measure for because of their rarity. Most of you know that over time alleles tend to fix and turn over, whether through neutral random-walk processes, or via positive selection. The HLA loci are cases in which many alleles seem to be extant within populations for millions of years (this post expresses formalisms which show why this is unlikely). The coalescence of some HLA variants with sister lines predates the diversification of hominoids. You may in some ways be more genetically similar on these loci to a chimpanzee than another human being! Because of the polymorphic diversity and cross-loci nature of tissue matching even with siblings the chance of match is just 1 out of 4. The chance of matching with non-relatives is about 1 in 20,000 (though I believe this number refers to white Americans in relation with other white Americans). Because different populations exhibit different HLA frequency profiles the chance of cognate permutations is greater within populations than across. This is why it is more problematic when ethnic minorities need to find a tissue match in the United States, and why it is doubly tragic that ethnic minorities tend be a disproprotionately small fraction of the pool. But what does this have to do with hybridization? Simple: the problems for biracial chidren in tissue matching are magnified because of their immunological uniqueness.
Consider the allelic profile of an individual at three loci:
X X X
X X X
Each X stands for a spot in the genome. The top row represents the contribution from one parent, the bottom row another, and the columns represent loci. You have two copies of each gene as you are diploid. Now, imagine a European child. The profile can be diagramed like so:
(premutations of alleles from one parent, conditional upon European allele frequencies)
(premutations of alleles from one parent, conditional upon European allele frequencies)
Similarly, an East Asian child:
(premutations of alleles from one parent, conditional upon East Asian allele frequencies)
(premutations of alleles from one parent, conditional upon East Asian allele frequencies)
What about the child of an East Asian and European parent?
(premutations of alleles from one parent, conditional upon European allele frequencies)
(premutations of alleles from one parent, conditional upon East Asian allele frequencies)
This child will exhibit a unique immunological profile generated by their likely novelty because they will bridge European and Asian populations, but, a tissue match is contingent upon a sequence of necessary matches. Though many Europeans will match the permutation inherited from one parent, and many East Asians the permutation inherited from the other, the combination of the two rows, so to speak, is very rare. This means that a tissue match can be very problematic for these individuals because they are novel combinations of two distinct populations. While East Asians and Europeans have a far greater chance of finding an appropriate match within their own populations, Eurasians need to look within a group of individuals who are also Eurasian, as they will exhibit the genetic variation which results in their particular combination of alleles across the loci.
A friend of mine emailed me and expressed the opinion that this was one of the most scary arguments she'd heard against interracial marriage. There have been scarier. In the early 20th century the eugenicist and biologist Charles Davenport did a series of studies on Jamaican children to show that black-white hybrids were inferior in fitness to their parental phenotypes. Unfortunately, Davenport's work was rather suspect even at the time (though accepted due to a priori biases). What Davenport was looking for is common in the animal kingdom, and it is termed outbreeding depression. Basically, two lineages when brought together exhibit a discordant genetic combination so as to reduce fitness. This can occur in animals like frogs which are
But this is the downside. There's an upside! First, the simple ones. Armand Leroi has outlined an argument:
...people of mixed ancestry should show the benefits of concealing recessive mutations. And this, I suspect, is the true meaning of Saira Mohan: half Punjabi, quarter Irish, quarter French and altogether delightful. She, too, is a mutant - but a little less so than most of us.
Basically, the reason that having offspring with siblings is so dangerous is that you are likely to share a pack load of lethal recessives and the chances of them being expressed are extremely high. That chance drops considerably with cousins, but the proportion of cousin-marriage offspring with recessive diseases is still rather high because the coefficient of relatedness of 1/8 means that there is a /18 chance of a allele at a locus being identical by descent, that is, it is the exact copy from the common ancestor. If you both carry a really bad mutation on your lucky matched copy, well, problems ensue. Hybrid vigor may result from a situation where mildly deleterious recessives that are expressed are hidden. Another argument is that heterozygosity confers benefits, that is, two different copies of a gene instead of matching copies. My own impression is that the heterozygosity argument is not well accepted today. Additionally, there are other possibilities, for example, synergistic positive epistasis, where novel genetic backgrounds do not lead to breakdown, but increased fitness. Some arguments for the maintenance of sex use the same rationale, even though sex is in the short term a losing strategy, it results in these novel combinations which can result in great increases of fitness over the long term (and there are other issues like Muller's Ratchet, but that's for another day). But I saved what I think the most solid point is for last, and it is the inverse of the point about tissue matching: rare immunological profiles maybe relatively insulated from common pathogens which are adapted to infect modal populations. In other words, the bugs which have learned to pathogenize Europeans, Asians, Eurasians as a whole, or Africans, might have a harder time with hybrids of these populations which are something altogether new. Over a lifetime this immune boost might result in a developmental headstart or edge. In the case of a plague or some other disease it seems that this group will be far more likely to be insulated from the ravages of the super-bug because that super-bug by its nature will probably be optimally designed to break down and circumvent the most common immune strategies, not the oddballs. There are other strange issues one could moot. For example, an admixed population should exhibit more phenotypic variation than the parent populations because it exhibits more genetic variation. Does this imply that it exhibits more fitness variation? That is, the hybrid population would have more extremely fit and unfit individuals than either parent population? Mechanistic forms of epistasis, recessive masking, etc. might account for this. One could imagine a peculiar model where this increased variance could lead to greater mean fitness in adulthood. Consider the variance of fitness in a population increasing. Now, imagine that fetuses below a threshold in fitness do not complete their term. The miscarriage rate in this population would be higher, but, as the variance increases, so long as the threshold of fitness is below the mean the remaining pregnancies completed to term will have higher median fitness! Do I believe in this scenario? Not really. But it could work. The point is that this is a complex issue. In the early 20th century biologists attemped to "prove" the orthodoxies of the day. Today it is in vogue to exclaim that interracial children are more "beautiful" and "healthier." There is even a book out, Breeding Between the Lines: Why Interracial People are Healthier and More Attractive, which makes the "consensus" argument which is dominant in our zeitgeist. Myself, I would state on average that there is probably a slight fitness payoff in an extreme outbreeding scenario. But the science of this is to be determined, and there is a lot of detail and nuance that can be added to the discussion.
In the early 20th century the eugenicist and biologist Charles Davenport did a series of studies on Jamaican children to show that black-white hybrids were inferior in fitness to their parental phenotypes. Unfortunately, Davenport's work was rather suspect even at the time (though accepted due to a priori biases). What Davenport was looking for is common in the animal kingdom, and it is termed "hybrid breakdown." Basically, two lineages when brought together exhibit a discordant genetic combination so as to reduce fitness.
Hybrid breakdown doesn't refer to the F1 hybrids. F1's are thought to exhibit hybrid vigor. Hybrid breakdown refers to decreased fitness in F2 hybrids or later.
By the same token, it's risky to be from any minority racial group seeking an organ transplant. The smaller the minority, the more dangerous.
The problem with medicine is that it tends to reify social norms, simply because it is biology applied to social ends. And, despite people worried about race mixing, the social norm in practice is racial assortment/separation. That's why racially mixed people are a novelty. What the above is saying is "Not many people are Eur/Asian, hence Eur/Asian HLA profiles are rare, so being a Eur/Asian seeking an organ transplant is dangerous (and maybe therefore few people should be Eur/Asian)."
rpm, thanks! replaced with a more general term....
I went to B&N last night to get that Breeding Between the Lines book, but they didn't have it yet -- have you read it? If so, is it worth buying or just checking out from the library?
For phenotypes I believe I log-normally distributed (whether on the basis of solid evidence or just everyday observation), I think the interracial increase in this trait is probably the epistatic freak of nature scenario. Beauty, scientific / artistic creativity, anything where "the whole is more than the sum of its parts."
The other thing is that F1 hybrids don't represent the initial intermingling between two liquids previously kept apart by a film, now mindlessly oozing together. It takes a certain something to want to bump uglies w/ someone who's quite noticeably different from you on the outside, so the parents won't be representative of their populations. The personality trait Open to Experience comes to mind, so the kids are less likely to adhere to tradition. Regardless of their factor-level score on Extraversion, the parents would probably score high on the facet of it called Excitement Seeking. (Hot, rebellious thrill-seekers -- no wonder there are so many mixed race porn stars!)
Actually, that'd make a good research project -- like the one on IQ among Eurasians in Hawaii. Wouldn't be encumbered by anti-HBD stuff since it would tend to celebrate the unique gifts of interracial harmony or whatever.
assman, remember that the key is better than expected values/fitness. i don't think it has to be superior to both populations necessarily to show some hybrid effect (though better than expec. could just be dominance).
Hmm... I need to read this in more detail and then hope to hell I can understand it. I'm European and my girlfriend is East Asian. But is this a scary argument againt interracial humping (you don't need to marry to carry) or is it an argument FOR it? After all, there are already quite a few mixed-race people (many of whom are totally hot). It would be irresponsible of us to not be providing more potential donors, right?
BTW, I'm in the middle of re-reading the Ursula LeGuin Earthsea books, where everyone's varying shades of brown - except a few outcasts on the edge of the world who won't play nicely with others. They have pasty white skin. I quite like her vision of a world where (almost) everyone has "gotten together", as it were.
it depends on your parameters. my own gf is not my race, so you an infer from that what my personal opinion is :)
le guin is quite conscious in fucking with race concepts. i think she is a little bit PC & ernest about it, but it is something different (e.g., the whites are obviously bad, the kargads). i like some of her short stories where she has dark-skinned humanoids with blonde hair and what not, that conflates our perceptions more naturally.
Agnostic,
Based on some rather unscientific research I conducted recently, I've found that Cuban hottie Vida Guerra exhibits a rather profound phenotype... certainly one to warrant extra study on hybrid vigor or whatever ;)
the above link (vida guerra) is NOT WORK SAFE. just a warning.
Reminds me of the Bullworth solution to racial problems: "We all need to keep f*ing each other till no one can tell the difference anymore."
Reminds me of the Bullworth solution to racial problems: "We all need to keep f*ing each other till no one can tell the difference anymore."
unfortunately, this will increase variation and types, not eliminate difference
In maize, some pairs of strains nick and some don't.
Could well be the same for humans.
Actually, I was thinking of the comments re LeGuin when making the Bullworth reference, not the overall topic of the article.
It's probably a good example of how popular understanding diverges from scientific reality that most people tend to assume that dillution of obvious visual differences (such as the skin color) suggest a more homogeneous population, when in fact the mixing of racial groups results in a much more fragmented gene pool rather than several disinct but fairly homogenous pools.
How long, I wonder, does it take these kind of genetic population mixing periods to even out? Do countries like Mexico show higher than average genetic diversity because the population there is the result of the mixing of European and Native American populations over the last 500 years, or has the impact of that already worked itself out?
Do countries like Mexico show higher than average genetic diversity because the population there is the result of the mixing of European and Native American populations over the last 500 years
mexico's european contribution from males is probably due to operational polygyny, so that would affect it.
when in fact the mixing of racial groups results in a much more fragmented gene pool rather than several disinct but fairly homogenous pools.
well, i was specifically pointing to the fact that in a admixed population the phenotypic range is theoretically at least that of the parent populations, and because of mixing & matching of traits, generally much greater. in other words, the world will not homogenize anytime soon even if racially random mating occurred, because more combinations will result. genetics is discrete, not blending....
Most people who propose the Bullworth strategy must surely know of a clear example of this: Brazil. Does everyone look the same, or even close? The best way to see if X will work is to see if anyone else has done it already.
Vida Guerra... you seen her "stolen" cell phone pictures? Rumor has it she just leaked some nudes of herself as a publicity stunt. Who cares, as long as we get to see her unfettered booty (it's always been trying to bust out of whatever she's wearing anyway). Like two heaping dollops of toffee ice cream!
If peaceful coexistence truly requires harmonious genotypes, then panmixia might not solve the problem unless there was uniform selection across the whole human population. Equalizing skin color might help east the psychological shock factor of seeing a person with a different color (kind of like seeing a red banana - it seems like some kind of primate visual-shock reflex). But if behavioral traits are really controlled by genes, then those need to be ironed out, some "one size fits all" personality parameters would have to be selected for.
Otherwise the world might change from people of different colors and different cultures and personalities fighting each other, to people of uniform color and different cultures and personalities fighting each other.
Has anyone ever really studied whether Brazilians have a smoother range of phenotypes than US folks? Or is this just some kind of "Tropicalist" (like Orientalist a la Said) mytheme in the Anglo world? Or is Brazil just a bunch of tannish Iberians with a part-African underclass, instead of a bunch of pinkish Celto-Germans with a part-African underclass?
My 2 cents....It appears to me that inter-racial breeding is riskier than intra-racial breeding, but its a risk that can pay off. Hence people tend to be attracted to exotic foreigners, but it can be more of an exciting 'sowing your wild oats' kind of attraction than a comfortable and lasting affinity. Cultural differences may be a bigger reason for this than genetic differences, but I think the risks and potential rewards are analogous in either case. I also think the feelings of a particular couple should be a relatively good measure of whether the risk is worth taking.
I think that Asian/European children are more often than not more attractive than their parents. The blend of personality and other mental traits is probably more important however, and I don't know enough mixed race adults to have an opinion about that.
For society as a whole, it seems obvious that some degree of inter-racial breeding is a good thing. Even if it doesn't work out well for certain individuals, it works out quite well for others. And in the long run natural selection tends to preserve what works.
Nu,
I think Brazil differes from the US in that the bulk of the population is admixed (Mulatto, Mestizo), with much smaller groups of either exclusively European descent or African descent individuals - and very few Native Americans. My brother's girlfriend is an admixed Brazilian (Mulatto) and all her family seem to exhibit the same general honey-brown color - like as if it has stabilized.
By comparison, Peru, IIRC, has 36 million people, 3 million are of European or Japanese descent, 18 million are admixed (Mestizo), and 12 million are pure Native Americans.
Another way interracial marriage might provide an unexpected health benefit or impairment -- we get a decent amount of help in the digestive process from our gut flora. They appear to have adapted to our intestinal tract, right? But then, not everyone's intestinal tract reflects the same history over the past 10,000 years of ingesting the same types of food. So, interracial hybrids could have novel intestinal tract phenotypes that either:
1) are completely outta whack with the ambient gut flora, causing what would otherwise be a fitness cost (may or may not be so in a modern civilization w/ all sorts of ways to alter one's diet & seek medical care, vitamin supplements, etc.); or
2) amplify the positive contribution of the gut flora, perhaps creating a more efficiently running system.
I speculate that the 2) is true b/c shortly after eating, I will violently belch for the next 30-60 minutes intermittently, though not due to GI upset / indigestion. I just do. Doesn't matter what type of food I ate either. I also have a freakishly high metabolism. Maybe my Japanese / Northwestern Euro genes have mixed so that my gut flora turn what would otherwise become waste or fatty deposits into gases of one sort or another. Some excrete by defecation, others pack on fat -- I just belch a lot.
Agnostic,
You're lucky. My admixture gave me a high metabolism and GI problems from both sides of the family. Hence I have to be extremely picky about what I eat, otherwise GERD and/or IBS kick in. It's especially annoying since I have low blood pressure and foods I need to eat to rectify that upset my gut to no end.
What really concerns me is the occurance of cancer in mixed races, since both sides of my family provide different forms of that.
What really concerns me is the occurance of cancer in mixed races, since both sides of my family provide different forms of that.
this doesn't make sense to me. seems like alternative oncogenes should complement.
agnostic,
Maybe you suffer from lactose intolerance - a lot of foods have some dairy in them??
spike, agnostic,
I'm Irish and not admixed - though my Mom is of English descent from the area of Britain with a lot of Sarmatian blood - but I suffer from lactose intolerance, GERD, asthma, allergies, Samter's Syndrome, and no sense of smell... and am somewhat Asperger like...
I think that all these conditions are in some way related to inflammation...
I wonder where in Brazil (or which social class) US-Brazilians are coming from. Brazil has a big myth of a "multicultural harmony," so people might claim to be more mixed than they really are. Is that color honey-brown, or just plain Euro-olive?
I've noticed that Americans experience cognitive dissonance with Latinos. They have an extremely hard time distinguishing Aztec from Moroccan or simply Euro-Iberian/Italian folk. Maybe because Americans are trained to look at color and not at features. It all seems to get lumped into a "sort of Caucasian looking but a few shades darker" category. After all, a Sicilian guy made a lot of money as the "Iron Eyes Cody the American Indian" billboard - and nobody seemed to notice.
Reducing things to color only works when you're dealing with extremes (like British and West African). It falls apart basically everywhere else.
Nu,
No the Brazilian female in question has definite traits of SSA ancestry, especially very full lips, wide nose, bodacious booty, and some non-typical of SSA ancestry, especially straight hair, high forehead - in fact skin color if anything, is less dark than one might expect from her other features...
Has anyone ever really studied whether Brazilians have a smoother range of phenotypes than US folks?
Color and genomic ancestry in Brazilians
Another article.
Does everyone look the same, or even close?
This one is actually quite easy to answer:
Absolutely not.
Brazilian passports are the most sought after in the international black market because anyone can reasonably claim to be Brazilian, whether you're Japanese, Nigerian or Swedish. The other was that until recently they were also relatively easy to fake.
I'll post here a couple of links so you can see it for yourself:
Gisele Bündchen
Gustavo Kuerten
LetÃcia Birkheuer
Edilson
LuÃs Gushiken
Mari Alexandre
Juliana Paes warning: not work safe
LavÃnia Vlasak
NÃvea Stelmann
Sabrina Sato not work safe either.
TaÃs Araújo
Elza Soares
Angélica Ksyvickis
Natália Nara
Jorge Bornhausen
Paulo Vanzolini
Matinas Suzuki Jr.
Ronaldinho
and
Pelé
This could go on and on. Seriously, what is wrong with the concept that Brazil is a diverse country?
How can one say to a loving couple that they shouldn't have children because they are an interracial couple and the child has a lesser chance of having a donor if the need arises?
People should never, ever live in fear.
Let the world and its inhabitants lead us into the future and progress humanity to the next level. I think our present pace is below sea level...we're sinking... gotta keep our heads and hearts above water.
Our concern shouldn't be who's having children, -its how many. Overpopulation of humans is a problem today and will be in the future. Gotta feed all them children; black, white, eurasian, asian or other.
I'm Eurasian and healthy as a horse. I'll be damned if I were aborted based on the fact that one of my parents was white while the other was asian. Poor reasoning for me!