Chapter 30 - Hybrid Vigor
There is no evidence that race-mixture as such produces bad results from the biological point of view. The social results of race-mixture whether for good or ill are to be traced to social factors."
"Statement on Race," United Nations, Unesco, 1950

    Egalitarians have argued that people of mixed race are in some ways superior to people of unmixed race, and therefore race-mixing is desirable. This seems inconsistent with their position that there are no significant genetic differences between races, but egalitarians are not strongly committed to consistency. That position is examined in this chapter.
    It will no doubt occur to readers that miscegenation seems similar to making a hybrid. We all know that hybrids are improved varieties, possessed of “hybrid vigor,” and perhaps other desirable traits. This book takes the position that the Caucasians themselves are hybrids of Cro-Magnons and Neanderthals. (Chapter 24). So why should miscegenation be any different? Won’t miscegenation just produce hybrids with superior qualities?
    “Hybrid vigor” (“heterosis”) is the phenomenon of hybrids growing more vigorously (bigger, stronger, faster) than either parent population (or than the average of the two parent populations). (Ekblom, 2000). In order to understand why hybrid vigor occurs, it is necessary to explain the technical terms “homozygous” and “heterozygous.” An individual is 100% homozygous if all of the alleles he inherited from his mother are paired with identical alleles inherited from his father; an entire population is “homozygous” if each individual in the population is homozygous and everyone has the same alleles for every gene. Thus, a 100% homozygous population is “pure” and “breeds true” because every individual has exactly the same alleles – identical “multiplets”; each individual in each generation is genetically identical and each generation is genetically identical to prior and future generations. 1
    In a 100% heterozygous individual, on the other hand, all of the alleles from the father are paired with alleles from the mother that are different; a population is 100% heterozygous if each individual is heterozygous and no two individuals have the same allele for any gene. Aside from a very few purebreds, all sexually-reproduced living things are heterozygous to some extent and there are no 100% homozygous populations. Similarly, it is unlikely that any population will be 100% heterozygous because some alleles are “fixed,” i.e., everyone has them. Thus, real populations will be “more homozygous” or “more heterozygous” than other populations or than they were previously.
    Due to mutation and selection, the longer a population has been isolated from other populations, the more likely it is to have acquired alleles by mutation that other populations don’t have. Intrabreeding passes those alleles around within the population, so that people within that population are more likely to share alleles than are people from different populations (Chapter 7), i.e., that population is more homozygous than is a population formed by combining that population with another population.
    Since an advantageous allele of a gene, i.e., an allele that increases reproductive success more than some other alleles of that gene that are in the gene pool, will increase in frequency in a population, populations will have mostly advantageous alleles. The smaller the population is, the sooner everyone within a population will acquire any advantageous alleles that have arisen and the sooner any less advantageous alleles that have gotten in to the gene pool will be eliminated from the population when the people who have them have less reproductive success. (Ridley, 1996, p. 285; Patterson, 1999, p. 40). Thus, the longer a population is isolated from other populations, the more homozygous it becomes as there will be only a single allele for more genes in the population, i.e., more genes go to “fixation.” Less advantageous alleles are seldom entirely eliminated, however, because they may be only slightly less advantageous, they arise faster than they can be eliminated, they are not expressed until after an individual has (at least to some extent) reproduced, and other reasons.
    Now, when two populations interbreed to form a hybrid population, each parent population has accumulated, over tens or hundreds of thousands of years, a unique set of alleles that is close to the optimum for the particular environment it has been in, and that environment includes the environment its own members have created, e.g., their history, culture, and accumulated knowledge. Inevitably, the two parent populations have lived in different environments, and the hybrid population will live in the environment of one or both of the parent populations. Thus, the hybrid population will not have the collection of alleles that are most advantageous for either of those environments, a substantial loss of fitness, i.e., their likelihood of successfully reproducing is lessened. 2
    Although populations have different percentages of each allele, those percentages change as the environment changes and selects for different combinations of the traits that the alleles code for. The percentage of each allele in a population increases or decreases, moving asymptotically towards the percentage that is optimum for that population in that environment, where that optimality is constrained by what is genetically and culturally feasible (e.g., removing harmful alleles by preventing carriers from breeding may cause more loss of fitness than letting them breed).
    When formerly separated populations in different territories intermix and interbreed, the percentage of each allele in the hybrid population will be approximately the average of its percentage in the parent populations, weighted by the relative sizes of the populations. Those percentages will be farther away from the optimal percentages for each population in their former territories, a loss in fitness for the hybrid population. And, unless the individuals in the hybrid population continue to move about in the combined territories and interbreed, thereby keeping their alleles at non-optimal percentages, individuals will tend to migrate to the territory that they are most adapted to and, by selection for adaptation to that territory, the percentages of the alleles in the population in each territory will once again gradually move towards the optimal percentages. In other words, without continual random interbreeding, two (genetically different) populations will once again form. As soon as nature is permitted to take its course, different varieties, races, and species will evolve all over again – egalitarianism requires a never-ending battle against nature. 3
    The longer a population remains isolated, the more inbred (i.e., homozygous), it becomes because, eventually, recessive alleles are either expressed and spread (if advantageous) or are expressed and eliminated (if less advantageous). Thus, isolation and inbreeding not only eliminate less advantageous alleles, but also increase the frequency of the expression of advantageous recessive alleles. Conversely, a population that has a large number of expressed recessive traits, e.g., blue eyes, has likely been isolated for a long time. 4
    Although the gene pool of an inbred population becomes more adapted to the population’s environment, it has less variation; an inbred population is more vulnerable to extinction because it lacks individuals with slightly different traits who can be selected should the environment change and make those traits more advantageous. On the other hand, a population that has less variation will be better adapted to an environment that is stable (Chapter 4, Rule 7) and will be more efficient at exploiting it than a population with unneeded variation. 5

                            Recessive Alleles
    When an allele from the father is paired with an allele from the mother that is not identical, one allele may be dominant and the other recessive, so that only the dominant allele is expressed, or a mixture of the two alleles may be expressed. If a deleterious allele is dominant, it is usually quickly eliminated from a population because its possessor is unlikely to reproduce or raise offspring to maturity. 6
    Populations will normally have a small proportion of deleterious recessive alleles (“DRAs”). A few DRAs are constantly being introduced into populations by mutation (or interbreeding with other populations) and a few are constantly being eliminated by the failure of the individuals carrying them to reproduce, so the percentage of deleterious recessive alleles in a population tends to reach a stable, equilibrium level. Interbreeding spreads both desirable recessive alleles and DRAs. 7
    Although DRAs will vary from only slightly disadvantageous to deadly, for the sake of clarity in a simple thought (“gedenken”) experiment, let us assume that they are all deadly. Let’s say that 50 white women breed with 50 white men and 50 black women breed with 50 black men. Each population maintains a stable level of 100 members, half men and half women. The 100 member white population has two identical DRAs, one DRA in one of the 50 men and one DRA in one of the 50 women, and so does the black population, but the white DRA is not the same as the black DRA. The 2% DRA level in the white and black populations (2% of the members have a DRA) will be maintained and there is a 1/2500 chance (1/50 x 1/50) that a male carrying one of the DRAs will mate with a female carrying the other DRA. If that happens, there is a ¼ chance that their child will have two copies of the DRA (½ x ½ = ¼) and will die. If the child dies, those two DRAs will no longer exist in that population until two mutations occur to replace them, one in the men and one in the women.
    Now suppose instead that the 100 whites interbreed with the 100 blacks (50 white women with 50 black men and 50 white men with 50 black women). In the resulting 200 member mulatto population, 1% will have white DRAs and 1% will have black DRAs. Although 2% of the population will have DRAs, in the first generation there will be no pairing of the two black or the two white DRAs. In other words, the first generation of the mulatto population will have no deaths due to the expression of the white or black DRAs. (Even if the mixing were less than 100% the number of deaths would still drop, but not to zero.)
    Individuals in the resulting mulatto population of 100 men and 100 women now breed among themselves. The percentage of white and black DRAs in subsequent mulatto populations will gradually increase to their stable level of 2% again, i.e. there will now be 4 white DRAs and 4 black DRAs in the mulatto population of 200, i.e., 2 white DRAs and 2 black DRAs in the men and the same in the women. The probability that a male carrying a white DRA will mate with a female carrying another white DRA is 1/2500 (2/100 x 2/100) and the probability that a male carrying a black DRA will mate with a female carrying another black DRA will also be 1/2500, so the probability that one of those two types of matings will occur is 1/1250. The probability that a mulatto child will inherit two copies of either the white DRA or the black DRA and will die is now twice as high as that a white or black child would have died in the two unmixed populations; miscegenation has doubled the chances that a child will die from having two copies of a DRA. 8
    Most of the time people, even in isolated racial or ethnic groups, need not worry about DRAs being expressed because the probability is low unless their mate is a close relative. Also, if a population has been inbred for a long time, there will be very few DRAs in it anyway.
    Although the decrease in deaths in first generation could be (and sometime is) called “hybrid vigor” it is not “vigor” so much as it is a single generation dilution of the two DRAs in the mixed population before the DRAs return to their equilibrium levels. Interbreeding temporarily reduced the percentage of DRAs at the cost of subsequently increasing the number of people who have them, thereby making their elimination more difficult and less likely.

                            True Hybrid Vigor
    True “hybrid vigor” occurs when inbred populations are interbred. The inbred populations that are used do not have DRAs, but do have advantageous alleles, dominant and recessive. (Simpson, 2003, pp. 601-602). How can that be accomplished? Well, it is accomplished all the time with plants and animals. Here is how it is done.
    Start with purebred (i.e., mostly homozygous) parent populations that are not obviously incompatible, e.g., one very large and the other very small. 9 Purebred parent populations are used because they “breed true,” that is, the offspring are all very much the same as the parents. If you start with mixed breed (mostly heterozygous) parent populations, you will just get a lot of mixed breeds and will produce neither a population with the desirable qualities you want nor hybrid vigor.
    Purebred populations are obtained by inbreeding. 10 Since close relatives have more of the same alleles than non-relatives do, if close relatives breed, some of the offspring will be more homozygous than the parents. (If the desired traits are recessive, the set of individuals who have more of the desired traits will be more homozygous.) If only the individuals who have the desired traits from each generation are selected for breeding, the population will become more and more inbred, because those individuals have more of the same alleles that code for those traits. Eventually, the population becomes homozygous, or nearly so, i.e., it is purebred.
    When purebred parent populations are being created by inbreeding closely related individuals, both desired and undesired traits coded for by recessive alleles will be expressed much more than in the parent population because the probability of two recessive alleles ending up in the same individual is greater. But, when that happens, those individuals are bred only if they have the desired traits. Individuals that don’t have the desired traits are culled (“purged”), 11 i.e., euthanized or given away as pets. In that way, each succeeding inbred generation has fewer and fewer undesirable traits and more and more desirable traits. 12
    Now crossbreed two or more purebred parent populations, each having a different set of desired traits, and, voila, hybrid vigor! 13 To see why, let us take two homozygous populations, “AA” and “BB,” where “A” is the complete collection of alleles in the “AA” population and “B” is the complete collection of alleles in the “BB” population and no A allele on any gene is the same as a B allele. When purebred population “AA” is crossed with purebred population “BB,” all the individuals in the hybrid population “AB” will have a mixture of all the “A” alleles from the “AA” population and all the “B” alleles from the “BB” population and will exhibit “hybrid vigor,” i.e., they will be healthier, stronger, and will grow faster than their purebred parents. 14 Why?
    If two heterozygous populations interbreed, each population having two different alleles for each gene in each pair of chromosomes (AB and CD), and the two populations do not share any alleles, the alleles for each gene in the two chromosomes of each individual in the resulting mongrel hybrids will be different (AC, AD, BC, BD). That is also true of the purebred hybrids, who are all “AB.”
    If we pick one individual from the purebred hybrids and one from the mongrel hybrids and compare their alleles, we see that both individuals are heterozygous, i.e., each allele of each gene in the chromosome inherited from the mother is different from the corresponding allele in the chromosome inherited from the father. But, in the purebred hybrid all the alleles in one of those two chromosomes were previously together in the mother and, in the other chromosome, they were previously together in the father. 15 In the mongrel hybrid, however, the combination of completely different alleles and crossover placed alleles in the two chromosomes that had never previously been together in the same individual. This suggests that because the purebreds were inbred, their alleles were together in many previous generations and had been selected for compatibility with other alleles as a necessary part of the process of forming a purebred population with the desired traits. The alleles in the hybrid populations were less compatible because they had not previously been together in the same individual, and therefore could not be, and had not been, selected for compatibility.
    In the first generation of the purebred hybrids, all the alleles from each parent are together in each pair of chromosomes, but in each subsequent generation crossover mixes them up so that they are in different chromosomes. As a result, hybrid vigor quickly dissipates, 16 which is why farmers have to buy new hybrid seeds each year.
    Individual humans, however, are a long way from being homozygous and, although races are somewhat inbred, they are a long way from being purebred. 17 It would simply not be worth the immense cost required to obtain hybrid vigor in humans, even supposing people wanted to do it, especially when the effect quickly dissipates anyway.

                            Selection and Culling
    When man makes a plant or animal hybrid, he carefully selects which offspring he will let survive and reproduce. Nature, too, selects ruthlessly and destroys thousands of crosses from different populations, leaving few, if any, hybrid survivors. (Patterson, 1999, p. 95). When the Caucasians arose, for example, there was no government aid to the less capable, and those who did not possess the most advantageous traits of both the Cro-Magnons and the Neanderthals simply died without issue. The very existence of the Caucasians in Europe proves that they, the hybrids, were more fit in Europe than either the Cro-Magnons or the Neanderthals who begot them.
    With miscegenation today, however, few of the hybrids fail to survive and reproduce because food, shelter, medical and dental treatment, and social services are provided for them, whether or not they are sufficiently productive to pay for them. Instead of letting natural selection take its course, as it did when the Caucasian hybrids were born, the state requires the more fit to reduce their own chances of surviving and reproducing in order to enhance the chances of the less fit surviving and reproducing. Any farmer with an ounce of sense knows that all his plants and livestock are not all genetically equal, and so he selects his seed for his next year’s crop from only the best of his plants and animals; only egalitarians tell every seed that with a little manure it can be the equal of any other seed, however unfit it is.
    In primitive populations that are barely surviving, genetically-defective individuals are quickly culled, but in First World countries, with surplus resources, modern medicine, and welfare, even individuals in whom severe DRAs are expressed, are kept alive and frequently reproduce, 18 gradually degrading the gene pool. Indeed, the less capable have more reproductive success than the more capable, another byproduct of egalitarianism. With domesticated plants and animals, humans purge individuals with the slightest fault, but with their own species, only the worst cases don’t breed, so the undesirable traits of DRAs are expressed at an ever increasing percentage. And, when there are no more resources to keep the unproductive alive they will attack the more productive, killing off the foolish geese that enabled them to do so.
    When the races interbreed, there is no plan to produce a human who is more fit or even one who is healthier, more intelligent, or otherwise more desirable, other than, perhaps, being “not white.” There is not even a plan to let the offspring fend for themselves and die off if they cannot do so. All the offspring are permitted to breed and no one is stopped from breeding. Worse, the non-productive are more fecund and, still worse, new deleterious mutations arise in each generation. The inevitable result is the enfeeblement of the entire species, a fate that awaits no species save man.
    Failing to cull is like trying to create a new breed of dog by putting different purebreds in an enclosure and letting them promiscuously bred while caring for all the pups. 19 You would not end up with a new breed, just a bunch of mongrels, and you will have destroyed all the hundreds of years of work that were required to create the pure breeds you started with. That is why you pay a lot more for a purebred dog, cat, horse, cow, sheep, or tomato seed, and why a mongrel dog or cat at the pound is free or nearly free. 20
    People inherently understand the concepts involved in breeding and readily apply them not only to plants and animals, but even to their own reproductive choices. Parents, being more objective and experienced than their children, can often instantly tell when their child’s choice of a mate is a bad one. Young people, too, may have flings with enticing, but unsuitable mates, yet when it comes to settling down, the genetically-controlled traits in a mate that determine their mate’s traits and their children’s traits usually become more important. 21
    The only practical way (genetic engineering would be incredibly difficult) to obtain a population with a high percentage of desirable traits and a low percentage of undesirable traits, is to isolate that population from other populations so that it becomes inbred, then select for breeding only those individuals who have the desirable traits. That is, in fact, what our ancestors have done for us and that is what we are thoughtlessly undoing by miscegenation.

    Another argument raised by the egalitarians is that races are isolated populations that have bred among themselves for tens of thousands of years (true) and they are somewhat inbred (also true). Incest is an extreme form of inbreeding, they continue, and we all know that incest produces horribly sick and deformed people. 22 Race-mixing introduces new blood and is therefore healthy because it is the opposite of incest.
    Incest may be culturally abhorrent, but it does not create DRAs – it merely increases the probability that they will be expressed (“inbreeding depression”) if they are present. 23 But some believe that the more inbred a person is, i.e., the more homozygous he is, the unhealthier he will be, even if he has no DRAs. In other words, they are arguing that homozygosity, in and of itself is, for some reason, unhealthy.
    There are, indeed, some disadvantages to homozygosity. Because a sexually-reproducing population that was 100% homozygous would be similar to an asexually-reproducing population (in both cases, the offspring are genetically the same as the parents), they would have the same problems that asexual populations have – inability to evolve by the selection of alleles already present in the population, vulnerability to predators, and an increased load of parasites who have specialized to attack that unique collection of traits. 24 So, to that extent, the egalitarians are correct, but races are a long, long way from 100% homozygosity, and those problems are not problems with real races. 25
    Other than those problems, however, there is no evidence or logical reason why 100% homozygosity is or would be harmful. 26 There is, with few exceptions, no harm in having a single gene in which both copies are identical, 27 so it is hard to see why having all genes with both copies identical would, in itself, be harmful. (Simpson, 2003, pp. 590-598, 606-607). Incestuous inbreeding of animals has been performed for multiple generations without problems. (Id., pp. 599-600). Most commercial plants and animals used for human food are highly inbred, so that all individuals are nearly identical in their nutritional requirements, medical needs, date of maturation, and behavior. No commercial farm could operate efficiently if each animal had its own requirements. If inbreeding were harmful, these farms would not exist.
    But there is no need for incestuous inbreeding in order to obtain the advantages of inbreeding. Any isolated ethnic group is inbred, yet can, and usually does, avoid incest. The absence of sexual desires towards people who look or smell too similar or are “nestlings” (raised together, the over-stimulation of familiarity dulling sexual desire), and one sex leaving the home discourages incest. 28

    “Genes do not work in isolation.” (Sapolsky, R., "A Gene For Nothing," Discover magazine, May, 2007, p. 32). Genes code for polypeptides that are used to make proteins that interact with other proteins and compounds in the body. If those interactions are between fully compatible compounds, the efficiency of the interaction is higher than if the compounds are not fully compatible. Each parent has thousands of collections of interacting compounds that, over many thousands of years, have been selected because they are compatible with other compounds present in that population. 29 Race mixing breaks up the collections of alleles that code for those compatible compounds. 30 During long periods of isolation where individuals in a population breed among themselves, a huge number of different combinations of alleles are expressed, i.e., tried out. Individuals who had combinations that did not work well were less reproductively successful, which eliminated some of the alleles from the genome, leaving behind fewer alleles for each gene, but alleles that worked well with the other remaining alleles. (Pusey, 1996).
    Because brain tissue has more complex interactions than other tissues, a decrease in compatibility may have a greater adverse effect on the brain than on other organs. Egalitarians take the position that if a black and a white are both intelligent then, since everyone is genetically equal, it is just as likely that they will have intelligent children as if they were both white. Not so. Certain traits, and intelligence is one of them, are not inherited in such a way that the children tend to cluster around the average of that trait in their parents. Instead, the children are in between the average of their parents and the average for their own population; this phenomenon is called “regression to the mean.” 31 For example, if the intelligence of both parents is above average, the intelligence of the children is also likely to be above average, but not as high as the parents, and if the intelligence of the parents is below average, the intelligence of the children is likely to be below average, but not as low as the parents. So, if an African couple both have an IQ of 85, which is above the African average of 67, their children are likely to have IQs between 67 and 85; if a white couple both have an IQ of 85, which is below the white average of 100, their children are likely to have IQs between 85 and 100.
    Consistent with the increased incompatibility of alleles 32 that results from race mixing, there is evidence that mixed races have more health and behavior problems. 33 For example, the child may have small teeth in a large jaw with gaps in between, or large teeth in a small jaw, resulting in crowded teeth. 34 In the brain, specialized areas of the cortex must be the right size relative to other parts of the brain or performance suffers. (See EMX2 gene).
    Mismatched alleles in mulattoes can lead to autoimmune diseases, such as arthritis and multiple sclerosis, where the immune system inherited from one parent attacks the proteins made from the other parent’s DNA. Ness, 2004. There are rearrangements, inversions, and duplications in the human genome that differ among the races and may cause incompatibility. There are also some non-genetic costs of race-mixing, such as cultural incompatibility and the spread of a disease that one of the parent populations is immune to but the other is not.
Figure 30-1
    The greater the genetic distance between two individuals, the greater is the incompatibility of their alleles. 35 Some part of the excess miscarriages, stillborns, and infant mortality among African Americans may result from “mismatches” between their European alleles and their African alleles, e.g., the father’s genes code for one set of proteins and the mother’s genes code for a different set of proteins that are not fully compatible with the father’s set. Compared to white parents, stillbirths are 17% higher for white mother/black father, 37% higher for black mother/white father, and 67% higher for black mother/black father; a similar relationship holds for low birth weight and neonatal mortality. 36 As genetic distance between the parents increases, their offspring become more sickly, then are no longer fertile, then are no longer viable, and finally, there are no pregnancies. (Fig. 30-1). By operating at the left side of the graph in Figure 30-1, DRAs are expressed, 37 but are removed from the population if the individuals who have them do not breed; advantageous recessive alleles are also expressed 38 and can more rapidly increase in frequency, which benefits the population.
    By operating at the right side of the above graph, miscegenation spreads DRAs throughout the mulatto population, increasing the number of individuals who have them and causing genetic incompatibility in the mulatto genome, weakening it; the presence of advantageous recessive alleles is diluted. 39

Chapter 31

Table of Contents


1. A 100% homozygous population is even more identical than identical twins because each twin is most probably not homozygous. Also, identical twins and clones drift apart genetically as they age. (Martin, 2005). Back

2.  If an advantageous allele has arisen in one population but not the other, a portion of the hybrids will have it, but that allele may not be accompanied by other alleles that enable it to perform efficiently. Back

3. To put it another way, to prevent populations from evolving and wiping out an egalitarian mongrel utopia, selection must be prevented. It is similar to economic egalitarianism where, once everyone is made equal in wealth and income exchange, if permitted, will soon make them unequal again. “.. if men are free, they won’t be equal.” (Putnam, 1961, p. 60). Foolish men are no match for persistent Nature. Back

4. (Chapter 4, Rule 14, corollary). If Eurasians express more recessive alleles than Africans (which seems likely, given that Africans have greater variation), that would lend support to the OoE theory because it would suggest that Eurasians were more isolated than Africans and Africans received their alleles from Eurasians, not the reverse. Also, the expression of recessive alleles in Europeans suggests that Europe was not invaded much by people carrying dominant alleles. Back

5. (Chapter 4, Rules 4, 7, and 11). Africans have more variation not because each population in Africa is more varied, but because the entirely of all the many populations in Africa collectively have more variation. Back

6.  On the other hand, although a dominant allele that increases reproductive success, such as an allele for health, good looks, or intelligence, would have spread quickly throughout a population prior to birth control, today that is not necessarily the case because those who have the allele may not want to reproduce. Back

7. For example, African Americans, a hybrid population of Africans and Caucasians, have picked up a Caucasian allele that increases their risk of heart disease (Helgadottir, 2006) and they may be at a higher risk of developing multiple sclerosis due to acquiring a European allele on Chromosome-1. (Reich, 2005). Back

8. (Lynch, 1997). Suppose the thought experiment is repeated, but this time the two populations are highly inbred and the non-DRA alleles are the same in all the whites and the same in all the blacks, but none of the white non-DRAs are the same as the black non-DRAs. Now, in the first generation mulatto population, every white non-DRA will be paired with a black non-DRA and none of the advantageous traits that resulted from having the same non-DRAs in all the whites and the same non-DRAs in all blacks will be expressed; i.e., even the first generation mulatto population will be less fit. Back

9. Often, the males are selected from one parent population and the females from the other. Back

10.  About 20 generations are required to produce mice that are as similar to each other as identical twins. (Zimmer, C., "Inside the Lab-Mouse Factory," Discover magazine, May, 2007, p. 33). Back

11. Purging reduces the genetic load of the population by decreasing the amount of useless and destructive genetic material that must be copied and carried. Back

12. A little physics again - the Second Law of Thermodynamics: in a closed system, entropy increases. As individuals are inbred to produce purebred lineages, their collections of alleles become more and more ordered. That is, out of the total number of alleles in the population, the probability that the sought-after particular collection of alleles would end up by chance in the individuals of the purebred population is very low. The collection of alleles in the individuals of a mulatto population, however, become more random, a much more probable outcome. Thus, hybridization creates a more ordered state, reducing entropy within the culled inbreeding population, while miscegenation creates a more disordered state, increasing entropy within the unculled randomly breeding mulatto population. Hybridization is creation, miscegenation is destruction. Back

13. The assumption is made that alleles in the purebred populations are compatible, i.e., they are closely related, so that the vigor of the hybrids is not reduced by incompatible alleles. Back

14.  New species are often formed in nature by this same process. Isolated groups become highly inbreed, then the environment changes so that they come into contact and breed. The hybrids have various mixtures of the traits of the two inbred groups. Only those with the most adaptive traits survive and form the new species. Back

15. That is true even with crossover because the grandparents also had the same alleles. Back

16. “Hybrid vigor,” when it does occur, “is the peculiar possession of the first cross.” “Further crossing of these hybrids results in a manifest decrease of vigor in subsequent generations. The second crosses are not so vigorous as their hybrid parents.” (Crew, 1927; quoted in Simpson, 2003, p. 601). Back

17. With an average of 14 alleles per gene, the percentage of homozygous genes will be small. Back

18.  (Dugdale, 1877). This may be why European populations have proportionally more deleterious genetic variations than African populations. (Lohmueller, 2008). Back

19. (Simpson, 2003, pp. 602-605, 732-733). Even after cross-breeding two or more parental stocks that are mostly homozygous and that have compatible and complementary traits that are unlikely to conflict, the resulting hybrids are bred with each other so that any remaining undesirable alleles are expressed and the alleles for those traits can be eliminated. Back

20. It is true that many purebred animals, especially dogs, have genetic problems. The reason is that people will pay a lot for them, even with their problems, and so they are not culled. Back

21. There is some evidence that women are able to discern which men will be dads and which cads just by looking at their faces. (Roney, 2006). Back

22. If inbreeding is harmful then inbred species should not evolve barriers to outbreeding. But they do. Such barriers may include different odors, songs, mating rituals, etc. Back

23. “Continuous crossing only tends to hide inherent defects, not to exterminate them, and inbreeding only tends to bring them to the surface, not to create them.” (Castle, 1930). But remember, inbreeding also increases the likelihood that advantageous recessive traits will be expressed. (Chapter 4, Rule 14). Back

24. A loss of vigor has been observed in a few small, isolated natural populations that have become more homozygous, but not in laboratory animals. A natural population, of course, faces parasites and a much more changeable environment than does a laboratory population. Back

25. On the other hand, because inbred parents share so many alleles they can be expected to be more “K” orientated, caring parents. (Thünken, 2007). Back

26. “Further, any racial stock which maintains a high standard of excellence under inbreeding is certainly one of great vigor, and free from inherent defects.” (Schwartz, 1999, p. 266). The Mennonites in Kansas have been mentioned as being an inbred, but intelligent and healthy, population. (Moore, 1987). Cleopatra was the seventh generation of brother-sister marriages, and brother-sister marriages were also practiced by the royal Incas, the Hawaiian Alii, and the Singhalese. (White, E. Doorway Papers by Arthur Custance, 1988, Chap. 1). Before the DRAs are eliminated, the offspring of incest are unhealthy; after they are eliminated, they are superior. Back

27.  Indeed, that occurs in most people. The exception is “balanced polymorphism.” Also, most people have multiple copies of some entire genes, which can actually be beneficial. Back

28. A delay in puberty in girls when fathers are in the home may also be an incest-avoidance strategy. (Matchock, 2006). Back

29. “[G]enes appear to operate in a complex network, and interact and overlap with one another and with other components in ways not yet fully understood.” (Caruso, D., "Change to gene theory raises new challenges for biotech," International Herald Tribune, July 3, 2007). Back

30. See the explanation for “True Hybrid Vigor,” above. An example of an incompatible gene is LTA4H. Back

31. Here is a possible explanation: Let’s say, for the sake of an example, that 20 genes, each with 10 alleles, determine genetic intelligence. They can combine in 1020 different ways. Assuming each allele is equally likely (a false, but simplifying assumption), if each of those combinations corresponds to an IQ and we plot IQ on the horizontal axis and number of combinations that give that IQ on the vertical axis, we should get a bell-shaped curve. Since each combination is equally likely, only a very few combinations will correspond to a high IQ and only a very few people will have those combinations. Two high IQ parents don’t have the same alleles, but they each have combinations of alleles that result in a high IQ. Their children, however, will receive mixtures of their parent’s alleles and the children’s combinations are more likely to be on the left (lower IQ) side of their parent’s combinations than on their right (higher IQ). So the children’s IQ regresses towards the more probable combinations, which are nearer to the mean.
    Some alleles will be mostly in combinations below the mean and some will be mostly in combinations above the mean. The combinations at the extreme right will have not only a subset of particular alleles, but will have only particular combinations within that subset. Thus, it is easy to knock a combination out of the extreme right end of the bell-shaped curve by simply substituting alleles that are mostly in combinations below the IQ of the parents.
    The more closely related the two high IQ parents are, the more likely they are to have the same alleles and the more likely it is that their child will have the same alleles, and the same combination of alleles, that gave the two parents high IQs. Thus, if all four grandparents and all eight great-grandparents had high IQs, the child’s IQ is not likely to regress towards the mean as much, i.e., he will “breed true.” On the other hand, the more genetically distant the parents are, the more likely the child is to receive different alleles and the greater his combination of alleles will differ from his parent’s combinations, so the more he will regress towards the mean. Thus, even assuming that the parents have the same high IQ, the IQ of a child is likely to be higher when both parents are white than when one is white and one is black. Regression to the mean also explains why black children of middle class parents are three times more likely than white children of middle class parents to drop to the lowest fifth in income. (Taylor, J. “Race/IQ Explanation Gap at ‘Achievement Gap Summit’,”, Nov. 13, 2007). Here are some other examples of regression to the mean: “Black children from the wealthiest families [i.e., higher IQ parents] have mean SAT scores lower than white children from families below the poverty line.” “Black children of parents with graduate degrees have lower SAT scores than white children of parents with a high-school diploma or less.” (La Griffe du Lion, 2000a). Back

32. It is not only alleles that can be incompatible, but strings of DNA. As discussed in Chapter 4, under “Recombination,” in the production of eggs and sperm, strings of DNA inherited from the parents are mixed up (“crossover”), and the strings may be incompatible. This may be the reason that two white-looking mulattoes can have a child that looks black. Epigenomes may also be incompatible. Back

33. (Choi, 2006). See (Richards, 2005 and 2006) and references cited therein. The mating of people with dissimilar genes may result in health problems in the offspring due to the failure of genetically-programmed incompatible biochemical or physiological pathways, a phenomenon known as “outbreeding depression.” These problems may increase with subsequent generations as more incompatible combinations of genes occur. “Adolescents who identify themselves as mixed race are at higher health and behavior risk than those of 1 race.” (Udry, 2003). Genetic similarity theory (Chap. 7) predicts that white mothers of mulatto children will not feel close to them, which is unhealthy for both mother and child. (Riley, 2006). White mother/black father couples invest fewer resources in their mulatto children than do either black couples or white couples. (Cheng, 2007). “…complexes of genes co-evolve in a population, acting harmoniously with one another to produce a high level of fitness. Different isolated populations may evolve different complexes of genes that interact well within a particular population, but poorly when the genes are mixed through cross-population matings.” (Lynch, 1997). “Blacks [i.e., African Americans, who are hybrids] tend to die sooner and younger from almost every cause but osteoporosis [because they have denser bones]. There are reports that even after all known causes are accounted for there is still ‘unexplained’ poor health among blacks. This difference is often ascribed to the stresses of ‘racism,’ but this is not a very convincing explanation. Recently, Surgeon General David Satcher appeared on television to point out that in America, black babies are 2-1/2 times more likely than whites to die in the first year of life. It is not clear how infants suffer from the stresses of ‘racism.’ “ (Whitney, 1999). There are also incompatibilities between whites and Asians. (Nystrom, 2008). The higher mortality of left-handers (Ramadhani, 2007) may also be due to incompatibility problems. Back

34.  (Bergman, 1998). “It is tempting to suppose that interbreeding would exacerbate malocclusion and increase the number of impactions.” (MacGregor, 1985). Back

35. A good example of genetic incompatibility is Haldane’s Rule, which says, “when in the offspring of two different animal races one sex is absent, rare, or sterile, that sex is the heterogametic [XY} sex.” In birds and butterflies, the female is the XY sex, but in mammals and fruit flies it is the male that is XY. (Birkhead, 2003, p. 150; Ridley, 1996, pp. 406-408). An X from one race and a Y from the other are less compatible than an X from each, so the percentage of male mulattoes resulting from Caucasian-African matings should be lower than the percentage in either parent population. (Holmes, 1927). “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.” (Baker, 1974, p.85). Back

36. (Getahun, 2005). Since this study was done in the United States, “black” refers to African Americans, who are already mixtures of about 75% African and 25% European. "Florida health statistics show that in 2005, the mortality rate for black infants was 4.4 times higher than that of white infants ... Researchers found that African women who come to the United States and have babies experience the same low rate of infant deaths as white American mothers [at least partly because they do not have those incompatible white alleles]. " (Ackerman, S., "Stress, Racism may Endanger Black Infants," The Tampa Tribune, Sept. 28, 2008). Also, (David, R., 2007). Back

37. Cousins among Muslims in England have more children with birth defects. (Gadher, D., “Minister Warns of ‘inbred’ Muslims,” The Sunday Times, Feb. 10, 2008). Back

38. Cousins in Iceland, a more homozygous and isolated island with a population of only 313,400, have more children. (Helgason, 2006); Icelandic men also have the world’s highest life expectancy for men at 79.4 yrs (2007). Back

39. Population genetics” treats the population as a reproductive unit; the optimal balance of inbreeding to outbreeding that will preserve advantageous alleles within the population while permitting the acquisition of advantageous alleles from other populations can be calculated. (Ardrey, 1966, pp. 138-141; Edmands, 2007). Back