View Full Version : The Health Consequences of Race Mixing

Tuesday, December 9th, 2008, 10:48 AM
The health consequences of race mixing among living organisms could be neutral, beneficial or harmful. This issue has been difficult to address in humans, but data from random, population-based studies have started coming in, and here we consider the first such dataset. The data in question come from J. Richard Udry’s National Longitudinal Study of Adolescent Health, which sampled a random, nationally representative school-based sample of U.S. adolescents in grades 7 through 12, during 1994-1995. [1]

Paper-based questionnaires were completed by 83,135 adolescents; a random sub-sample of these individuals plus some individuals in the school roster that had not completed the paper-based questionnaire, totaling 18,924 adolescents, were interviewed at home. The data are reported for the home-interviewed sample. Racial classifications are based on self-report; the participants were allowed to pick multiple racial categories to describe themselves. Table 1 shows participant characteristics. The participants were asked if they were Hispanic/Latino, but this was not considered to be a racial category. 86% of those who only chose “other” race also described themselves as Hispanic, and 46% of those who described themselves as Hispanic only chose “other” race. 72% of those identifying as American Indian also picked another racial category, usually white.


The data are presented in terms of odds ratios and statistical significance, both of which are briefly explained in the next paragraph, which knowledgeable individuals can skip. The odds ratio (OR) is the number of times something is more prevalent in one group compared to another. Thus, OR = 2.0 means a two-fold greater prevalence, OR = 1.3 means a 1.3-fold greater prevalence, OR = 1.0 means no difference, OR = 0.5 means half as prevalent, and so on. A statistically significant difference is a difference that most likely represents a genuine difference between the groups compared rather than a difference due to chance factors alone. If the probability that the difference obtained is due to chance is less than 5%, then the difference is typically considered statistically significant, which is denoted as p < 0.05; similarly, if the probability that the difference obtained is due to chance is less than 1%, then this is designated as p < 0.01. All statistically significant differences in Tables 2-4 (p < 0.05) are marked by an asterisk. On the other hand, due to inadequate sample size, genuine differences may not reach statistical significance in a study, although trends toward differences may be clear.

Table 2 shows that mixed-race individuals had an across-the-board higher incidence of health and behavior problems; the specific health problems addressed were assessed in terms of whether they occurred frequently or every day of the previous month.


Given the overall picture in Table 2, sample size limitations, and the fact that the sample is random and representative, all values in Table 2 that are clearly greater than 1.00 but not statistically significant can be considered as genuinely reflecting increased likelihood of health/behavior problems among mixed-race adolescents, and this also applies to Table 3.

Now, it may be that adverse outcomes vary by race combinations. To examine this issue, Table 3 compares various mixed-race combos with their single-race counterparts on health/behavior issues. The general pattern seen in Table 2 is also seen in Table 3, i.e., irrespective of which races are combined, there is an overall increase in health/behavior problems among mixed-race adolescents.


Let us address one confound in interpreting the data in Tables 2 and 3. It is commonly observed that a disproportionate number of white women who end up with black men are obese. Obese women tend to have elevated testosterone levels. [2, 3] Some portion of testosterone is converted to dihydrotestosterone (DHT), which amplifies the effect of testosterone at certain targets. [4] DHT is also one of the culprits in the genesis of acne. [5] Therefore, a higher incidence of, say, acne in black/white-mixed offspring with a white mother could simply reflect inheritance of the genetics of elevated androgens from the obese white mother rather than an effect of race mixing.

The point above needs to be considered in a more general scenario. When the races occupying the same geographic region differ in status, as in present-day Western societies, members of the high-status race who marry those of a lower-status race tend to have low status within their group. There are, of course, many examples to the contrary: Carmen Electra (mostly white) with Dennis Rodman (black), Heidi Klum (white) with Seal (black), and David Bowie (white) with Iman (Somali), among others. However, the aforementioned trend is clear, which raises the possibility that the negative correlates of race mixing are largely related to the unhealthiness of one or both parents rather than the deleterious effects of race mixing. This potential confound can be addressed by statistically controlling for demographic variables.

The authors controlled for age, sex, verbal IQ, grade point average, family structure (living with one or both parents), and family education; education can act as a proxy for socioeconomic status, and given an inverse relation between socioeconomic status and obesity in white women, [6] education can also act as a proxy for obesity in the white mothers of the mixed-race adolescents. Controlling for all these factors left the general picture seen in Tables 2 and 3 unchanged; some statistically significant odds ratios lost statistical significance, but the ones greater than 1.00 can still be considered significant for the reasons addressed above, and there were very few instances of greater-than-1.00 odds ratios diminishing to less than 1.00. Therefore, one can conclude that the negative health/behavior consequences of race mixing are related to race mixing per se rather than the variables controlled for.

The authors mention that the most common explanation of their find, which has also been reported by others using non-random samples, is that stress associated with identity conflict or struggle with identity formation is the culprit, but they also note that there is no proof in this regard. [1] Indeed, it is difficult to believe that struggle with identity formation is responsible for an across-the-board increase in health/behavior problems in mixed-race adolescents. How does struggle with identity formation lead to a higher incidence of skin problems?

An across-the-board increase in health problems should be evaluated in light of the basic architecture of physiological control, wherein the brain and the autonomic nervous system (ANS) are especially relevant. As is seen in the figure below, the ANS is involved in the autonomic (involuntary; automatic) regulation of organs, and its abnormalities could easily be behind Udry’s data.


ANS abnormalities are implicated in behavior problems such as excessive aggression, [7-11] atopy (a group of diseases such as asthma, skin problems such as eczema and psoriasis, allergies, runny nose, sinusitis, migraine), [12-16] headaches, [17-22] and a variety of health problems (see any textbook of medical physiology). Further, damaging some portions of the brain in rats increases the likelihood of cocaine or stimulant dependence, [23, 24] and something similar undoubtedly applies to humans, too. Besides, a number of brain abnormalities are common to both depression and drug dependence, [25] and substance use is more prevalent among mentally ill individuals. [26]

Therefore, to the extent that race mixing may increase the likelihood of non-optimal genetic correlation structures, it may be expected to adversely affect organism-level physiological control, which may very well account for Udry’s data. Alternatively, since part of the ANS deals with stressors, chronic social stressors could themselves cause a number of health problems. In this regard, the data in Tables 2 and 3 do not vary as a function of whether the adolescent is living with one or two parents or as a function of family education, which can act as a proxy for socioeconomic status. Being teased/ostracized for being mixed race also requires consideration, but it cannot be argued that during the time period of the childhood years of the Americans examined, a substantial number of the mixed-race children would have experienced ostracism/discrimination due to being mixed race, especially since a number of them would have grown up in large metropolitan areas, which are known to be more diverse and tolerant. Moreover, the general preference in the African-American community is to prefer African-Americans with lighter skin, [27, 28] and lighter-skinned African-Americans also tend to have higher IQs than their darker counterparts (Table 4, [29]), which should reduce academic stress. In other words, black/white-mixed individuals, who would typically be assigned and raised as African-Americans, are not necessarily really worse off compared to their darker counterparts with respect to being ostracized/marginalized.

Additionally, given white preference for Caucasian features and to the extent that Asian-Americans are envious of some of the facial features of whites, Asian/white-mixed individuals are less apt to be teased for their facial features than the less mixed Asians-Americans. And once again, there is no proof that struggle with identity formation explains Udry’s data. Also, the typical mixed-race adolescent with a white parent should have no doubts as to whether he is white; he wouldn’t look anything like a white person. Further, the data in Tables 2 and 3 do not vary as a function of age, which is relevant because the mixed-race individuals should have resolved their racial identity by their late teens.

On the other hand, there exist several examples in the animal literature where matings between more genetically distant individuals within the same species/different races result in offspring that are less healthy than the parents, on average, [30-37] and this cannot be blamed upon struggle with identity formation. There also exist examples of hybrid vigor, but nothing remotely close to hybrid vigor is seen in Udry’s data.

Consider also the fact that the genetic correlation structures manifesting as different races are so distinct that when a computer was asked to classify DNA data (326 microsatellite markers) from 3,636 individuals self-identifying as either white, East Asian, African-American, or Hispanic, into clusters, without being told which DNA sample came from which racial group, the computer clustered the DNA data into 4 groups, classifying all but 5 individuals into the correct self-identified racial group. [38]

Therefore, a parsimonious explanation of the across-the-board negative health correlates of race mixing in Udry’s data is that race mixing involving notably different races such as human races, by increasing the likelihood of non-optimal genetic correlation structures, increases the likelihood of deleterious effects.

Udry’s data are compatible with the likelihood of race mixing improving one or more parental traits in some mixed-race offspring, who may be better off than both parents on multiple counts, provided that a greater number of mixed-race offspring are overall worse off than both parents. The former possibility is surely not implausible given that the tremendous racial and species diversity out there implies that nature does not rule out equally-well functioning/better functioning novel genetic correlation structures, which could be brought about by race mixing, though the chances of improvement would typically be slim if more distant races are involved.

Further, those identifying as mixed-race in this study would generally have greater genetic admixture than those identifying as single-race. It is seen in Table 2 that those identifying as mixed race have worse health than even populations known to be highly admixed (American black, Native American, Hispanic). This could be accounted for if one assumes that first-generation hybrids who have the worst health/behavior problems would disproportionately not be very successful in reproducing, i.e., the healthier mixed offspring could, within a few generations, set up a mixed-race population that is healthier, on average, compared to the first-generation hybrids, but for this mixed-race population to approach or exceed the overall health of the original single-race populations, it would take many generations of [naturally] weeding out the unhealthy and settling toward a novel population-typical genetic correlation structure that corresponds to good health (more on this and on hybrid vigor in a subsequent post).

To conclude, it is irresponsible for any scientific organization to pretend that race mixing has no adverse health effects and it is obviously inappropriate to portray race mixing as desirable or virtuous.

Extra stuff (for those interested in additional details):

Table 4 compares mixed-race adolescents with their single-race counterparts on several measures. The GPA (grade point average) and the PVT (picture vocabulary test) categories feature the percentage of individuals in the 75th percentile of the entire sample.


Some of the responses to self-identified race differed between the school-based and home-based assessments (16% of entire sample). Over 90% of the respondents self-identifying as white only, black only, or Asian only at school, self-identified as the same race at home; the changes involved adding/substituting “other” race. Somewhat less than half the respondents picking multiple races at school picked the same categories at the home interview, and to the extent that those identifying as multiracial in school identified as single race at home, given the picture in Table 2, these individuals are likely making the single-race individuals look worse. 34% of those identifying as American Indian only at school identified as white only at home, and 77% of those identifying as white/American Indian at school identified as white only at home, but American Indians were a miniscule percentage of the study sample. The inconsistent responses among the mixed-race adolescents may have resulted from context (school vs. home), assessment technique (paper-based vs. interview), ambiguity of question asking about race, or lack of a fully developed racial concept at the time of the assessment. [1]

Literature cited:

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3. Sowers M, Beebe J, McConnell D, Randolph J, Jannausch M: Testosterone concentrations in women aged 25-50 years: associations with lifestyle, body composition, and ovarian status. Am J Epidemiol 2001, 153:256-264.
4. Dadras SS, Cai X, Abasolo I, Wang Z: Inhibition of 5alpha-reductase in rat prostate reveals differential regulation of androgen-response gene expression by testosterone and dihydrotestosterone. Gene Expr 2001, 9:183-194.
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18. Harle DE, Evans BJ: The optometric correlates of migraine. Ophthalmic Physiol Opt 2004, 24:369-383.
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21. Sanchez del Rio M, Reuter U: Pathophysiology of headache. Curr Neurol Neurosci Rep 2003, 3:109-114.
22. Shechter A, Stewart WF, Silberstein SD, Lipton RB: Migraine and autonomic nervous system function: a population-based, case-control study. Neurology 2002, 58:422-427.
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32. Garnier-Gere PH, Naciri-Graven Y, Bougrier S, Magoulas A, Heral M, Kotoulas G, Hawkins A, Gerard A: Influences of triploidy, parentage and genetic diversity on growth of the Pacific oyster Crassostrea gigas reared in contrasting natural environments. Mol Ecol 2002, 11:1499-1514.
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Thursday, December 11th, 2008, 02:27 AM
I don't know about that. I have heard of studies that show more psychological problems in mixed race children.

From my observation though at least with black/white mix there seems to be some hybrid vigor in a lot of the cases. I see ugly out of shape black and white have a fairly attractive healthy looking mixed child. Though it may be the black is already part white to begin with as the majority of blacks in the US are. Not saying every case is like this, but a lot of them are. Physically I think race mixing tends to help those with defective genes. I think it is because the two parents aren't likely to have the same defects.

I don't know if you have heard of animals breeding back to an older extinct form but you can look it up on wikipedia. Forget the term for it. Also noticed racially mixed people in some rare cases look like cavemen or seem to take a more primitive appearance than either pure race. Rather interesting.

I also noticed that pure blacks seem to be rather docile. For whatever reason when you mix that with white you get a hyper agressive individual usually prone to criminal behaivor, socially disruptive behavior etc. For whatever reason doesn't seem prevalent to such a high degree in either pure parent. The American black population as a whole seems to retain these traits. Pure blacks from Africa typically are much more calm and they may be willing to commit violent acts but they don't act out as agressively. They also don't seem as intelligent as the mixed raced blacks.

So from what I can tell studies say the I.Q. of racially mixed people are generally in the middle between the two parents and gravitate towards the average between the two races. Physically I think there is a benefit when two genetically unhealthy individuals race mix. For already healthy individuals no benefit, possibly some lack thereof I would presume because genes of related individuals evolved in compliment of each other. Psychologically though there seems to be problems in race mixed people more so than in the parents.

Thursday, December 11th, 2008, 10:06 AM
Something miscegenators do not think about: the odds of finding a suitable donor match in case of need are extremely lowered.

USA Today: Multiracial patients have tough battle to find marrow matches (http://www.usatoday.com/news/health/2005-01-30-mix-marrow_x.htm)

The hopes of his parents, both doctors in San Jose, Calif., immediately turned to a bone marrow transplant, but they soon learned some distressing news — Luke's ethnic heritage made him a tough match.


Sarah Gaskins, Luke's mother, has Japanese and European ancestors and his father, Lam Do, is Vietnamese-American. Because bone marrow matches usually are made with a relative or someone with the same racial or ethnic background as the patient, multiracial people rarely have success.

"It's tragic," said Lam Do, who specializes in internal medicine. "Your chance of finding a donor is so low, it's like winning the lottery. And most people are unaware of this."

Tuesday, May 5th, 2009, 12:14 AM
On the other hand, mixing within one's own meta-ethnicity, but with different sub-races increases a child's immunity considerably.

Tuesday, May 5th, 2009, 01:09 AM
On the other hand, mixing within one's own meta-ethnicity, but with different sub-races increases a child's immunity considerably.
Source? Reference?

Tuesday, May 5th, 2009, 07:27 AM
Source? Reference?

I heard it on a Discovery Channel 2 hour special on attraction, so I cannot actually give you a source. I know I shouldn't make statements without a ready source, but it seemed an important and relevant addition to the thread. Sorry...:(

However, I can explain this phenomenon, the way Discovery explained it to me. Because immunity is hereditary, every child gets the immunity of both parents, so the more different the bloodline, the higher the number of separate immunities passed on to the child.

Since most sub-races share many genes, they also share many immunities. So, when reproduction takes place within a sub-race, the child is genetically purer and therefore with less varied immunities.

Wednesday, June 30th, 2010, 08:21 PM
I raise and breed livestock. There is absolutely no doubt in the field that crossing different breeds generally results in a more vigorous and resilient off-spring in the first generation cross.

However, this is not an argument against pure breeds, for 2 reasons:

1. The stabilized hybrid of the crossbreeding in subsequent generations does not usually show the vigor of the first cross, and may well be inferior to the pure breed parents.

2. The pure breed is essential if you want a specialized animal. A bloodhound is the best tracker, a greyhound is the fastest, a Holstein produces the most milk.

For example, say a European population has very high IQ, but certain unique recessive genetic diseases, like jews. Cross the population extensively with Africans, and you will certainly reduce the genetic disease, but you will also lose the mental specializations.

Saturday, March 19th, 2011, 08:17 AM
In many cases, the two different gene pools (isolated for a long enough time to be called races) will have different health problems. Inbreeding is not especially grand, random outbreeding probably isn't either. Selecting for healthy traits in the first place is a good idea.

If the health problems can "cancel" each other out (say for example, it's an autosomal recessive trait, so that two of the same gene are needed to create it), then breeding out of one's group (in this example, one's group would all be genetically similar, therefore more of that recessive allele in it) would be an improvement.

This idea that marrying within the "broader" ethnic group (Norwegians marrying Germans?) being "better" than, say, a Norwegian marrying a Japanese person, is not supported by any academic literature that i know of. I'd love to see the citations.

Tuesday, April 5th, 2011, 04:43 AM
Not to mention the struggle mixed raced people go through when they need a HLA match for bone marrow transplants...it's close to impossible to find donors in places like Brazil and Mexico. They die for no good reason, there are simply no HLA matches for them.

Monday, February 20th, 2012, 01:25 AM
Blacks are susceptible to Sickle Cell Anemia, and mixing with them will produce offspring that are also susceptible to the disease. Race mixing is very destructive and not in any way beneficial.