Miscegenation Problems

                
Mixedrace children suffer from more health problems
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1448064/
Race-mixing leads to outbreeding depression & pairings of non-complementary traits.
A massively well-funded study of over 100,000 schoolchildren found that “Adolescents who identify themselves as mixed race are at higher health and behavior risk than those of 1 race.” Indeed, even when controlling for education, socioeconomic status, and other factors, there is an across-the board higher rate of health risks amongst mixed race adolescents than mono-racial adolescents.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1448064/
One study found that White-Asian mixes had a 2x higher rate of being “diagnosed with a psychological disorder, such as anxiety, depression or substance abuse.”
http://www.eurekalert.org/pub_releases/2008-08/uoc--baa081108.php
A study on Black-White mixes in agreement found that ”When it comes to engaging in risky/anti-social adolescent behavior, however, mixed race adolescents are stark outliers compared to both blacks and whites.” This holds true despite being raised in similar environments to mono-racial children.
http://www.msu.edu/~renn/RHE-_mixed_race.pdf
Often race-deniers and cultural Marxists will bring up Haldane’s rule, arguing that since races can mix and create fertile offspring, the genetic distance is not too great. Haldane’s rule is “when in the offspring of two different animal races one sex is absent, rare, or sterile, that sex is the heterogametic [XY] sex.”
http://www.nature.com/scitable/topicpage/haldane-s-rule-the-heterogametic-sex-1144
Indeed, although Black-White mixes are not sterile and males are not absent, males (the heterogametic sex) are more rare than females.
http://www.jstor.org/pss/1537084
The argument regarding Haldane’s rule is also meaningless because different species in the animal kingdom can breed and still produce fertile offspring. The wolf (Canis lupus) and the dog (Canis lupus familiaris), the coyote (Canis latrans), and the common jackal (Canis aureus) are separate species yet can all interbreed and produce fertile offspring.
http://www.jstor.org/discover/10.2307/3671304?uid=3739600&uid=2&uid=4&uid=3739256&sid=47699085472247
Two species of orangutan (Pongo abellii from Sumatra and Pongo pygmaeus from Borneo) can interbreed despite having different chromosomal numbers.
http://www.nytimes.com/1995/02/28/science/orangutan-hybrid-bred-to-save-species-now-seen-as-pollutant.html?pagewanted=all&src=pm
The common chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus) and many species of birds, such as the pintail (Anas acuta) and the mallard (Anas platyrhynchos), can interbreed as well.
http://www.sciencedaily.com/releases/2007/04/070420104723.htm
http://birdaz.com/blog/2011/02/24/mallards-the-weird-and-the-wonderful/
The gibbon and the siamang can also interbreed to produce a hybrid
http://www.ncbi.nlm.nih.gov/pubmed/451603
http://www.ncbi.nlm.nih.gov/pubmed/1060807
Some species that aren’t even in the same genus can interbreed.
http://aob.oxfordjournals.org/content/74/2/111.full.pdf
Black Americans are a hybrid race of around 22% White ancestry
http://genomebiology.com/content/10/12/r141
This 22% ancestry is the cause of multiple negative health effects due to genetic incompatibility. Indeed, consistent with Haldane’s rule, unmixed Blacks from Africa and White Americans do not have the same rate of birth problems that hybrid American Blacks have: “In 2005, the mortality rate for black infants was 4.4 times higher than that of white infants… African women who come to the United States and have babies experience the same low rate of infant deaths as white American mothers.”
http://t1nyurl.com/6tr9e6t (docs.google)
“Indiscriminate interbreeding between distinct forms, whether ‘species’ or markedly different races, is not generally beneficial. The defect may show in a change in the sex-ratio of the offspring, probably caused by the early abortion of members of one sex, generally the male in the case of mammals.”
http://www.amazon.com/Race-John-R-Baker/dp/0936396040
LTA4H, or “leukotriene A4 hydrolase” is found on chromosome 17. An allele of this gene increases the risk of heart attack (the #1 cause of death in America) in Blacks by more than 250%, but only 16% in Whites. The 30% of Whites with this allele have counteracting genes, while the 6% of Black Americans who obtained it through race mixing do not.
http://www.ncbi.nlm.nih.gov/pubmed/16282974
The average rate of success for mixed race couples is around half that of same race couples, 0.127 compared to 0.213.
http://www.jstor.org/stable/4145377
There is evidence that the more similar the two people are, the happier their marriage tends to be.
https://www.sciencedirect.com/science/article/pii/019188699190057I
A study in Iceland showed that 3rd cousin marriages are the most fertile and successful. Suggesting that mating within one's ethnic/racial group would be more beneficial than outside of one's ethnic/racial group.
http://www.sciencemag.org/content/319/5864/813.abstract
One study showed that people tend to find their own face when morphed into the opposite sex most attractive, even when he/she doesn't know it's his own face, strongly suggesting that people typically prefer those who look like themselves, in other words their own racial/ethnic group.
http://www.psyc.nott.ac.uk/research/vision/jwp/papers/pentonvoak1999.pdf
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
As an example, a White mother of mixed-race child would have more genetically in common with a random White person on the street than with her own child.
If such a dramatic and fundamental alienation from your own parents if not horrific enough, With a mixed-race child diagnosed with leukaemia, every member of the child's own family becomes an incompatible donor for a bone-marrow transplant, and finding a compatible donor is unlikely:
>One obstacle to finding a matching donor was her mixed ethnic background. Her father is black, with West Indian and Panamanian roots. Her mother is white, with Russian-Jewish roots. In addition, only 5 percent of registered donors are black.
http://www.nytimes.com/1996/04/18/sports/baseball-rod-carew-s-daughter-dies.html
Bone Marrow Transplants: When Race Is an Issue
>''Compared to organ transplants, bone marrow donations need to be even more genetically similar to their recipients. Since all the immune system's cells come from bone marrow, a transplant essentially introduces a new immune system to a person. Without genetic similarity between the donor and the patient, the new white blood cells will attack the host body.
http://www.time.com/time/health/article/0,8599,1993074,00.html
Race matters when a patient needs a stem cell or marrow transplant
>If you become ill with a blood cancer or other disease that requires a stem cell transplant, here's an uncomfortable fact: Your race matters. Diversity is a strength in much of life, [citation needed!] but it's a curse when finding a stem cell donor match.
http://articles.washingtonpost.com/2013-08-05/national/41085742_1_stem-jeffrey-chell-ancestors
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The Race for Ancestral Genetics in Clinical Trials
>A seasoned cancer researcher would never set up a study in which all the ill patients were, say, Canadian, and all the healthy controls were Japanese. And yet cancer researchers risk making a similar mistake if they overlook genetic information that fleshes out what many of us like to think of as race or ethnicity, some experts say.
>Fortunately, awareness of how ancestral genetics might contribute to risk of disease and drug response in people has risen over the last several years. Studies that look directly at the problem are on the rapid rise, and this increased interest has biotechnology companies lowering the cost of tests that determine genetic ancestry, thanks to a little competition. However, experts have yet to decide on how to genetically define ancestry, suggesting examining anywhere from a handful to hundreds of gene variants.
>Not including information on the race or ethnicity of study volunteers could skew disease risks as stronger or weaker than they really are.
>"Alzheimer's disease is the poster child for this problem," says pharmacogeneticist Esteban Burchard, M.D., of the University of California in San Francisco. A variant of the gene ApoE4 is a strong genetic risk factor for early-onset Alzheimer's disease, and the characteristic most likely to raise or lower that risk is race.
>"It occurs in about 20% of the African American population, and it means nothing. It occurs in about 6% of the Japanese, and it makes their risk six times higher [than that for white people]," Burchard said. "Something about being Japanese unleashes the wrath of the gene, and something about being African American attenuates it."
http://jnci.oxfordjournals.org/content/98/18/1270.full
BiDil
>The FDA have approved a heart failure drug called Bidil, but only for blacks, as blacks do not benefit from conventional heart failure drugs.
http://online.wsj.com/article/SB116096445875393515.html?mg=com-wsj
Sickle-Cell Disease
Sickle cell anaemia is a condition found almost exclusively in blacks, about 1 in 4 west Africans carry the gene for it, almost no whites do. Any whites who carry the gene most likely have a black ancestor.
As a result of population growth in African-Caribbean regions of overseas France and immigration from North and sub-Saharan Africa to mainland France, sickle cell disease has become a major health problem in France. SCD has become the most common genetic disease in this country.
https://en.wikipedia.org/wiki/Sickle_cell_anemia
Invasive species: Genes Are Destroyed With Admixture/Racial Mixing
Extinction by hybridization:
>Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially problematic for rare species coming into contact with more abundant ones. Increased use of molecular techniques focuses attention on the extent of this underappreciated problem that is not always apparent from morphological observations alone. Some degree of gene flow is a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence.
http://www.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.27.1.83
The Island Model with Stochastic Migration:
>It is supposed that the migration rate and the immigrant gene frequency are independent of each other in each generation, and each of them is independently and identically distributed in every generation. The treatment is confined to a single diallelic locus without mutation. If the diploid population is infinite, selection is absent and the immigrant gene frequency is fixed, then the gene frequency on the island converges to the immigrant frequency, and the logarithm of the absolute value of its deviation from it is asymptotically normally distributed.
The above implies that if you have two genes in some frequency in the immigrant population, under one way migration that frequency becomes the dominant frequency on the island.
>We investigated various cases of the island model with stochastic migration. If the population is infinite, the immigrants have a fixed gene frequency and the alleles are neutral, the gene frequency on the island converges to that of the immigrants.
What this means is that the genes initially on the model island, in effect, disappeared.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1213928/pdf/163.pdf
Evolution with Stochastic Fitness and Stochastic Migration
>Migration between local populations plays an important role in evolution - influencing local adaptation, speciation, extinction, and the maintenance of genetic variation.
>A number of studies have shown that when per capita population growth rate is treated as a random variable, rather than a fixed parameter, then directional evolution is influenced not only by the expected fitness of each phenotype, but also by the variance and other moments [23], [28]-[33]. This follows from the fact that, in a closed population, change in mean phenotype is inversely proportional to mean population fitness
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007130
Figure 1. The consequences of a negative correlation between fitness and immigration rate:
<top figure in picture
http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0007130.g001&amp;representation=PNG_M
Figure 2. The influence of the variance in immigration rates, on the expected change in mean phenotype:
http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0007130.g002&amp;representation=PNG_M
<bottom-left in picture
Essentially, when the variance in the immigration rate is small it results in a negative phenotypic change on the mean phenotype of a population, as the migrant phenotypes predominate.
Figure 3. The relation between variance in immigration, selection, and in an island-continent model:
http://www.plosone.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pone.0007130.g003&amp;representation=PNG_M
>bottom-right in picture.
>The curves show the change in mean phenotypic value assuming a mean phenotypic value as decided by a population's selection.
>The variance in migration is shown in descending value on the curves.
Though the mean rate of migration is the same on all the curves, it is clear that the the island can still get close to fixation of the phenotype favoured there, so long as the variance in immigration is high.
So for this figure, assuming that migration is an indefinitely persisting condition, migrants will prevent the local island favored phenotype from remaining intact, as they are essentially working against selection.
_____________________________________
The models/simulations in these studies are based on understanding evolutionary genetics, on how migration influenced evolution, which makes them excellent sources for metaphors on the effects of modern immigration rates in human populations.
Genes Are Destroyed With Admixture/Racial Mixing
Nonindigenous species can bring about a form of extinction of native flora and fauna by hybridization and introgression either through purposeful introduction by humans or through habitat modification, bringing previously isolated species into contact. These phenomena can be especially problematic for rare species coming into contact with more abundant ones. Increased use of molecular techniques focuses attention on the extent of this underappreciated problem that is not always apparent from morphological observations alone. Some degree of gene flow is a normal, evolutionarily constructive process, and all constellations of genes and genotypes cannot be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species’ existence.
http://www.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.27.1.83
Allopatric speciation
Allopatric speciation or geographic speciation is speciation that occurs when biological populations of the same species become vicariant — isolated from each other to an extent that prevents or interferes with genetic interchange. This can be the result of population dispersal leading to emigration, or by geographical changes such as mountain formation, island formation, or large scale human activities (for example agricultural and civil engineering developments). The vicariant populations then undergo genotypic or phenotypic divergence as: (a) they become subjected to different selective pressures, (b) they independently undergo genetic drift, and (c) different mutations arise in the populations’ gene pools.[1]
The separate populations over time may evolve distinctly different characteristics. If the geographical barriers are later removed, members of the two populations may be unable to successfully mate with each other, at which point, the genetically isolated groups have emerged as different species. Allopatric isolation is a key factor in speciation and a common process by which new species arise.[2] Adaptive radiation, as observed by Charles Darwin in Galapagos finches, is a consequence of allopatric speciation among island populations.
https://en.wikipedia.org/wiki/Allopatric_speciation
https://en.wikipedia.org/wiki/Speciation
Reproductive isolation - Sexual isolation by behavior or conduct
Even where there are minimal morphological differences between species, differences in behavior can be enough to prevent mating. For example, Drosophila melanogaster and D. simulans which are considered twin species due to their morphological similarity, do not mate even if they are kept together in a laboratory.[3][12]Drosophila ananassae and D. pallidosa are twin species from Melanesia. In the wild they rarely produce hybrids, although in the laboratory it is possible to produce fertile offspring. Studies of their sexual behavior show that the males court the females of both species but the females show a marked preference for mating with males of their own species.
https://en.wikipedia.org/wiki/Reproductive_isolation
>Picture: drosophila fruit flies are popular choices for these types of experiments.
http://evolution.berkeley.edu/evosite/evo101/VBDefiningSpeciation.shtml
Just imagine what a few extra years of separation could have done for certain human populations…
Well...
>"Human races are evolving away from each other," Harpending says. "Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity." He says that is happening because humans dispersed from Africa to other regions 40,000 years ago, "and there has not been much flow of genes between the regions since then." 
http://unews.utah.edu/old/p/120607-1.html
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Patterns of Situational
Identity Among Biracial and
Multiracial College Students
https://msu.edu/~renn/RHE-_mixed_race.pdf
Health and Behavior Risks of Adolescents with Mixed-Race Identity
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1448064/
Bone Marrow Transplants: When Race Is an Issue
http://content.time.com/time/health/article/0,8599,1993074,00.html
Biological Problems with Mixed-Race Families, Marriages Relationships and Adoptions
http://sociobiologicalmusings.blogspot.ca/2011/10/problems-with-mixed-race-marriages-and.html
Why are there deformities in male hybrid flour beetles while female hybrids are spared? Haldane’s rule: the male beetles have the heteromorphic sex chromosomes.
http://www.nature.com/scitable/topicpage/haldane-s-rule-the-heterogametic-sex-1144
Inclusive fitness in human relationships
J. PHILIPPE RUSHTON
http://www.humanbiologicaldiversity.com/articles/Rushton%2C%20J.%20Phillipe.%20%22Inclusive%20fitness%20in%20human%20relationships.%22%20Biological%20Journal%20of%20the%20Linnean%20Society%2096%20(2009).pdf
Genetic similarity, human
altruism, and group selection J. Philippe Rushton
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.134.6512&rep=rep1&type=pdf
>Migrations causing useful genes to disappear
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1213928/
>A third cousin is the optimal mate (balances inbreeding depression with outbreeding depression):
http://www.sciencedaily.com/releases/2008/02/080207140855.htm
>Mixed race people suffer from catastrophic shortage of organ donors, leaving many to die of treatable illness:
http://www.time.com/time/health/article/0,8599,1993074,00.html
http://articles.boston.com/2009-05-28/news/29263326_1_national-marrow-donor-program-mixed-race-multi
racial
>Biracial Asian Americans are twice as likely as monoracial Asian Americans to be diagnosed with a psychological disorder.
http://www.news.ucdavis.edu/search/news_detail.lasso?id=8732
Prematurity and Low Birth Weight as Potential Mediators of Higher Stillbirth Risk in Mixed Black/White Race Couples
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867623/
"There is a much higher suicide rate among mixed race children – they are five times more likely to commit suicide than someone of a singular race.
Hybridization shatters the form entirely into separate units of characteristics, and these units get jumbled up again each time they get passed on. People see attractive half-castes and think that the children will inherit the same characteristics, but it is impossible for them to be passed on like that, as they separate out again into the individual races’ features ensuring there is no unity of form to be passed on. Since Black genes are dominant and White genes are recessive, Mulattoes will always look more Black than White.
Blood transfusions are not possible between the races (yet they are possible between cats and dogs) and neither are bone marrow transplants. A mixed race person stands little chance of finding a donated organ that will not reject their mismatched body, since the organs are irreconcilably different as well. Obviously, the skin is different (the largest organ of the body), but so are the lungs, testicles, brain and kidneys. One of the most important differences between the races is the rate of hormones that each produce. Hormones control our emotions, our pain control, our sensitivity – all the different feelings that affect our behavior are correlative with various secretions from different glands. Mixed race individuals can have a different rate of secretions to that needed for the particular organs that they have ended up with, which can cause highly unstable temperaments. This is caused by the same conflicting racial characteristics that result in things like having a Negro skull but Caucasian skin, or a Caucasian skeleton with Negro skin. Rather than having each organ being partially Caucasian and partially Negro in a harmonious blend of the two, some of the organs will be Negro but some will be Caucasian. So you might get White testicles in a predominantly Black body for instance, or a Black brain in a White body. In a mixed race person who appears to be mainly Negro, there is no way to predict whether all his organs are too. Negroes have higher testosterone rates than Whites and are more aggressive and less emotionally-balanced because of this, but at least their organs are intended for that amount of testosterone.
Hormone irregularities are also linked with depression and not surprisingly there is a very high rate of depression, as well as all other health problems, among mixed race individuals when compared to non-mixed individuals." -NJ
Genealogy has contributed to Margot's rare antigens. Yaser is half-Syrian, a quarter Siamese and a quarter Scottish. He grew up in Roehampton. He has a "funny name but is a south London boy". Vicki, who is from Wolverhampton and met Yaser boarding an easyJet flight to Nice, is half-English, half New Zealander. Yaser says: "As the world increasingly becomes a melting pot donors become more difficult to find."
http://www.standard.co.uk/lifestyle/london-life/go-team-margot-stephen-fry-and-david-tennant-join-internet-search-for-bone-marrow-donor-for-one-year-9087356.html
Rory the cat's life saved with a blood transfusion from a DOG after eating rat poison (and an hour later he was purring and eating biscuits) [Blood transfusions between cats and dogs may be more compatible then transfusions between the different races of man]
http://www.dailymail.co.uk/news/article-2397891/Rory-cats-life-saved-blood-transfusion-DOG-hour-later-purring-eating-biscuits.html
Devan would need a marrow transplant. The prospect of going through chemotherapy for a second time and needing a transplant is daunting to anyone, but it's especially harrowing if — like Devan — you're of mixed race. Multiracial patients often have an incredibly hard time finding life-saving marrow matches. When Devan, whose father is Caucasian and mother is part Indian, was first diagnosed with leukemia, his family did a search of the international marrow registry that contains over 14 million donors and came up empty. "We knew there was nothing out there for him," Tatlow says.
Compared to organ transplants, bone marrow donations need to be even more genetically similar to their recipients. Though there are exceptions, the vast majority of successful matches take place between donors and patients of the same ethnic background. Since all the immune system's cells come from bone marrow, a transplant essentially introduces a new immune system to a person. Without genetic similarity between the donor and the patient, the new white blood cells will attack the host body. In an organ transplant, the body can reject the organ, but with marrow, the new immune system can reject the whole body.
http://content.time.com/time/health/article/0,8599,1993074,00.html
The Red Cross website page also notes:
"....Some patients require a closer blood match than that provided by the ABO positive/negative blood typing. For example, sometimes if the donor and recipient are from the same ethnic background the chance of a reaction can be reduced. That’s why an African-American blood donation may be the best hope for the needs of patients with sickle cell disease, 98 percent of whom are of African-American descent...."
http://www.redcrossblood.org/learn-about-blood/blood-types