To understand much of this article, especially the specific examples to follow, an introduction to some basic genetics terminology is in order. For those already acquainted with this genre of the biological sciences, the next couple of paragraphs will serve as simple review; however, those unaccustomed to the science should familiarize themselves with the concepts so as to be able to follow the author’s logic.

All of an individual’s genetic components are collectively called the genome. Chromosomes are structures within the nuclei of cells which carry the genes and function in the transmission of hereditary information. Biochemically, chromosomes contain a linear strand of DNA, which is the genetic material, as well as proteins which are bound to the DNA and give it an organized structure. The gene is a unit of heredity that occupies a specific location on a chromosome, and which determines a particular characteristic in an organism by directing the formation of a specific protein. The locus is the physical location of a gene within a chromosome. An allele is a possible form of a specific gene: it is one part of a pair or series of genes that occupies a precise position on a particular chromosome, or locus. The genotype refers to the genetic composition of an individual, and is usually expressed in terms of the alleles for particular genes. In turn, the phenotype is said to be an organism’s outward appearance, which is determined by the genotype. A specific attribute determined by a gene or group of genes or called a character.

In most cases, there are two alleles occupying a single locus. An individual is said to be homozygous for a gene if he or she has two identical copies of the same allele, and heterozygous if he or she has two different alleles for this gene. An allele is said to be dominant if, in the heterozygous condition, it determines the phenotype; conversely, an allele is recessive if its presence is masked by the dominant gene in the heterozygous state. Recessive traits are only expressed phenotypically in homozygotes for such a gene.

Darwinian fitness, usually abbreviated simply as fitness, refers to the extent to which an organism is adapted to or able to produce offspring in a particular environment. Fitness is a relative measurement; namely, it is the likelihood that a phenotype will survive and contribute to the gene pool of the next generation as compared to other phenotypes. Inbreeding is mating between two genetically related individuals (or breeding within an isolated population group), while outbreeding is the breeding of unrelated individuals, i.e., individuals from different populations. Since there are degrees of relatedness within members of a population, there is said to exist a coefficient of inbreeding which can be drawn from a pedigree analysis, which uses genetic information from family trees. Inbreeding is in no way synonymous with incest! The latter would theoretically correspond to a maximum coefficient of inbreeding for humans, but in any case is a social or cultural term rather than a scientific one.

Additional definitions will be provided for new terms as they are encountered. Those described above should serve to facilitate the comprehensibility of this document; they will, however, by no means serve as a replacement for delving into the subject matter in greater depth, which is necessary in order to truly appreciate evolutionary biology.

The Biology of Race

by hate edge

Race has become somewhat of a nebulous and even controversial term, and has often become misconstrued by those who understand it purely as a social, rather than a biological concept. If we are to understand the social implications of race, we must first explore race in a biological context, as after all, even human history cannot be abstracted from natural history.

What is race?

Scientists who work within the fields of biology use a system to categorize the earth’s organisms, called taxonomy. As proposed by Ernst Mayr in 1942, the biological species concept, or BSC, is the standard definition used for species, the fundamental category of taxonomic classification. According to the BSC, “species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” “Many species occupy a wide geographic range and are divided into discrete populations. A population is a group of individuals of the same species that can interbreed with one another,” meaning that they are in physical proximity to one another at a concurrent point in time.

“A large population usually is composed of smaller groups called subpopulations, local populations, or demes.” One “can consider a deme not only as a population of individuals but also as a population of groups isolated relative to certain traits. Thus the population of a given organism has levels. Total population over a large area, the global population, consists of numerous local populations, or demes, isolated in varying degrees from one another; each deme consists of a number of trait groups.” Over time, as adaptation to a given environment through natural selection occurs, various populations of a single species will undergo evolutionary divergence as they acclimate themselves to their respective habitats. It is by means of this divergence that subpopulations or demes arise.

In biology, the term “race” is synonymous with “subspecies,” a taxonomic group that is a division of a species and which usually arises as a consequence of geographical isolation within groups of a single species. Subspecies are thus tantamount to subpopulations or demes. There are said to exist human races because the human species has incurred geographic isolation throughout the course of natural history; thus a variety of populations of humans have arisen which bear disparate genetic traits, or exhibit differences from other human populations with regard to the frequency of hereditary traits.

Confusion often arises when the term race is used in an oversimplified context which solely denotes skin color. From a biological perspective, a race cannot be divorced from its geographic and environmental components, which no less than drove the evolution of such a deme. In ages where populations remained in relative isolation, groups were fairly easy to categorize based on their geographic location, their language, and any culturally distinctive features—in short, what comprises an ethno-culture—which varied correlatively with groups’ genetic configuration. This correlation between evolutionary divergence in relation to ethno-culture is most conclusively displayed by evidence which shows that “genetic differences among populations parallel their linguistic differences…suggesting that both genes and language have a common history of divergence in isolation (Cavalli-Sforza et al. 1994).” “Models of gene-culture co-evolution (e.g., Boyd and Richardson 1985; Cavalli-Sforza and Feldman 1981; Durham 1991), in which genotypes may differ in their propensity to adopt a cultural trait, and culture in turn may affect fitness and thus alter allele frequencies,” have also been posited by a number of scientists.

Divergences occurred on multiple levels during the evolution of the human races. In some cases genetic differences were readily ostensible, such as in the form of distinct morphological features, or were outwardly unapparent but seen in other evolutionary respects—such as physiological or immunological characteristics and adaptations. For example, there are documented cases which demonstrate how genes of a single locus can confer for either a disease or a beneficial adaptation—both exclusive to the population group—with the outcome being merely dependent on the alleles in this locus. One could cite the tradeoffs in resistance to malaria (in the heterozygous allelic state at the b-hemoglobin locus) at the expense of potential sickle-cell anemia (in the homozygous recessive state) in some African populations or contrast the effects of a gene which in its mutant state causes cystic fibrosis in persons of northern European ancestry, while in heterozygotes confers for a reduction in the loss of body fluids due to bacterial infection (Zielenski and Tsui 1995). Examples in the literature are abundant on the subject, and elaboration in further detail is beyond the scope of this article, as explaining the particularities of the genetics of individual populations is not its aim.

In line with the biological understanding, it may be said that at one point in time what was called a race in the context of human populations was more or less synonymous with ethnicity. However, as technological advancements made possible the migration of large groups of people en masse, the potential for multi-racial countries arose. Where once only larger metropolitan centers of international trade saw the coalescence of distinct peoples in the interest of economics, eventually millions around the globe would transport themselves, as increasing industrialization afforded surges in the population growth of many countries, but without a corresponding rise in the work that was available. Gradually, in these multi-racial societies, as many cultural elements—and to a large extent, the races themselves—became amalgamated, ethno-cultures proper became defunct, and the term race encountered a shift in usage. Eventually, the appellation was divested of the depth of its original significance, and became the idiomatic equivalent for “skin color” in American English. Nevertheless, because the original meaning of the term race lies in overwhelmingly greater accord with the biological definition, the classic denotation shall be employed.

How have the different races arisen?

Understanding how the various human subpopulations have evolved is as simple as comprehending population dynamics between closely related organisms, regardless of whether they are species or subspecies. This is because evolution is an ever-present, ongoing phenomenon—it is occurring now! Speciation is taking place at this point in time between two populations which relatively recently could have been said to be a single species. Subpopulations evolve en route to speciation. If one wishes to understand the races as they have arisen in time, rather than merely observe a single, discrete static point in natural history, it is useful to posit a working paradigm for evolutionary divergence for which semantics do not act as a stumbling block to one’s ken.

Evolutionary theory denies any notion of teleology, or goal-oriented culmination, because this would imply consciousness on the level of genetics. (However, one may find that even biologists often speak of nature with a teleological or purposeful tone. This is due to the fact that humans will inevitably project their own consciousness onto the objects and processes about which they speak—a rule to which this author is no exception.) There exist no anticipatory causes in nature; rather, the information in an organism’s DNA which codes for everything from behavioral development to adaptive characteristics “has been shaped by a historical process of natural selection, meaning that this information has survived and multiplied to a greater extent than DNA sequences which contain different, or no, information.” Therefore, to ask why the races evolved would be teleologically loaded—it would put the effect before the cause, which is simply illogical! (For purposes of clarification, a caveat must be stated: the teleonomic processes that can be observed in the natural world are those which owe their “goal-directedness to the operation of a program,” the program in this case being DNA, which of course evolved through the process of natural selection.)

Natural selection is most commonly misunderstood by those who believe it to be no more than a game of chance—yet little could be farther from the truth! While it is true that chance alone cannot produce complex structures, the only indeterminate level of evolution occurs during meiosis, when “the genes an individual inherits from its parents are recombined by independent segregation of chromosomes and by crossing over within chromosomes.” Natural selection is a deterministic process, not a random one—it is subject to antecedent environmental causes, or stressors. “The random processes of evolution, mutation, and genetic drift do not in themselves result in the evolution of complexity;” these processes merely give rise to variation among individuals, and allow the fixture of this variation into a population in the form of polymorphisms. Evolution only occurs relative to the stressors of a particular environment, and that particular environment is subject to change over geological time. Therefore, a species had better continue to evolve to its changing environment or else it will no longer remain extant. The deliberate direction of evolution is always towards adaptation to the environment when selection is in effect. This is why evolutionary divergence is seen throughout natural history, and it is the means by which the various human races evolved. It is also why any sort of racial superiority cannot be argued from a universal standpoint, but only relative to the environment in question.

Those who ascribe an outside, intelligent designer to the process of evolution often underestimate the tremendous extent of time it takes for a species to acclimate to its habitat, and fail to notice just how much “work”—in the form of selective screening—is involved when so many marvelous instances can be found in which it would appear that a species has perfected adaptation relative to its environment.

Yet evolution is an imperfect process. That humans share a single orifice which serves as an opening for both the respiratory and digestive systems could be considered somewhat shoddy planning, as it presents an opportunity for individuals to asphyxiate upon their food. Nevertheless, evolution is an amazing phenomenon, if one takes into consideration just how intricately creatures have been able to adapt to their environments. Over the course of many generations, groups of fruit flies feeding upon a specific type of fruit in isolation can develop a genetic preference for that fruit, as evidenced through behavioral and metabolic experiments, while bacteria can become specialized for the metabolism of certain types of simple sugars, so much so that when faced with a foreign carbohydrate source, the initial generations of bacteria will be unable to digest the sugar. Biologists have shown that it indeed takes numerous generations to acclimatize to a specific environment—and these results are from studies on some of the earth’s simplest organisms! Imagine the degree of specificity involved in organisms with relatively complex physiological pathways.

Occasionally, when the complexity of evolutionary genetics is oversimplified, various scientific principles are misconceived. For example, the concept of heterosis, commonly called “hybrid vigor,” is often popularly referenced—albeit erroneously and out of context—by those who herald miscegenation to be a sort of panacea for eliminating deleterious recessive alleles. Those who espouse such a notion subscribe to a logic which says that the phenomenon of overdominance—the condition of a heterozygote having a phenotype that is better adapted than that of either homozygote—implies that outbreeding will ensure the heterotic state. Yet such reductionism reveals a spurious understanding of genetics. “Genes do not exist in isolation. Each is embedded in a genome containing thousands of other loci with diverse functions. Two or more genes may affect a single character or different characters. Moreover, each gene is linked to certain other genes, meaning that they are physically associated on the same chromosome.” Thus, while it is true that immediate inbreeding increases the frequency of deleterious recessive alleles, leading to the phenomenon of inbreeding depression (a decline in components of fitness found in offspring whose parents are directly related individuals), the inverse yield will not be had by outbreeding, as gene function cannot be measured linearly. Heterosis is only observed in “hybrids produced by crossing two different inbred lines,” meaning the hybrid vigor observed is only a relative qualitative assessment. The Dominance Hypothesis proposed by Charles Davenport in 1908 explained what in retrospect is more or less common sense: when the two different inbred strains “are crossed to each other, the resulting heterozygotes are homozygous and do not suffer the consequence of homozygosity for deleterious recessive alleles. In other words, the dominance of the beneficial alleles explains the observed heterosis.” Such a phenomenon is most often observed in agriculture—in plants and organisms with relatively simple genomes; however, since immediate inbreeding practices are seldom had in human populations—mostly for the fact that resulting deleterious homozygous recessive alleles result in severe genetic deformities, if not death—hybrid vigor (observed once crossing two such resultant offspring from disparate genetic lines) among humans is not well documented in the literature. On the other hand, inbreeding has been employed by humans for developing agricultural breeds for millennia, and is the only means for developing strains with characteristics that the breeder desires. What’s more, “about 85 percent of the genetic variation in the human species is among individuals within populations (Nei and Roychoudhury 1982),” rendering inbreeding—that is, breeding within a population—no more likely to result in less fit offspring than would outbreeding.

In fact, because genetic pools of even a single subpopulation have already been selected through myriads of generations of genetic screening, hybridization with members of a different population is, evolutionarily speaking, disadvantageous. Such hybridization is deleterious to the hybrid—as it no longer possesses the genes which coded for adaptation to a single, specific environment, but instead bears an amalgamated genome which does not confer for any habitat-specific adaptations—as well as the parents, whose fitness is reduced if the hybrid does not survive to reproduce.

As a model, one could again posit the example of Malaria, which showcases the heterozygote advantage at the b-hemoglobin locus in various African and Mediterranean human populations (Cavalli-Sforza and Bodmer 1971).

One allele at this locus, sickle-cell hemoglobin (S), is distinguished by a single amino acid substitution from normal hemoglobin (A). At low oxygen concentrations, S hemoglobin forms elongate crystals, which carry oxygen less efficiently and cause the red blood cells to adopt a sickle shape and to be broken down more rapidly. Heterozygotes (AS) suffer slight anemia; homozygotes suffer severe anemia (sickle-cell disease) and usually die before reproducing. However, if the red blood cells of heterozygotes are infected by the sporozoan protozoan (Plasmodium falciparum) that causes malaria, the cells are broken down more rapidly than in “normal” heterozygotes (AA), so the growth of the protozoan is curtailed. In parts of Africa with a high incidence of falciparum malaria, the frequency of S is quite high because heterozygotes survive at a higher rate than either homozygote. The heterozygote advantage therefore arises from a balance of opposing selective factors: anemia and malaria. In the absence of malaria, the balancing selection yields to directional selection, because then the AA genotype has the highest fitness… Several other hemoglobin mutations similarly provide heterozygous resistance to malaria, such as those responsible for thalassemia anemia, most prevalent in Mediterranean regions. The various mutations tend to have different geographic distributions within malarial regions, because if one such mutation has attained high frequency in a given area, a different mutation that provides a similar protection against malaria cannot increase in frequency if it is rare (Hartl and Clark 1989). Only under exceptional circumstances can heterozygous advantage maintain three of more alleles as a stable polymorphism.

The evolutionary divergence between populations is great enough that unique genetically encoded mechanisms have evolved to what superficially appears to be a singular environmental stressor—these immunological response systems are each particular to their given geographic habitat. Thus, the evolutionarily disadvantageous effects of hybridization become apparent. For example, if hybridization were to occur between members of the African and Mediterranean populations referenced above—even if each parent genotypically displayed its respective autochthonous heterozygous advantage, the probability would be greatest that the offspring would not have the genes for either of these defense mechanisms to malaria. This is because the S allele is unlikely to be found outside of the aforementioned African population, as it poses no selective advantage outside of its origin. Presumably, the same rule holds true for the alleles of the Mediterranean population. Such evidence demonstrates that race must be understood as the demic level of the population, because outside of this context, biologically, it cannot be qualified!

Unsurprisingly, complex systems have evolved which enable populations to remain, genetically speaking, in relative isolation. These isolating mechanisms, the biological barriers to gene flow, make it such that “the members of a subpopulation are far more likely to breed among themselves than with other members of the general population.” Isolating mechanisms are classified into reproductive barriers of two types. “Prezygotic barriers prevent or reduce the likelihood of the formation of hybrid zygotes,” in many cases taking the form of “positive assertive mating, i.e., nonrandom mating between individuals of like phenotype or genotype. Postzygotic barriers are factors that reduce the fitness of hybrid zygotes by reducing their survival or reproductive rates.” It must be remembered that in no way did these isolating mechanisms arise through any teleologically-oriented cause, but that they are simply emergent phenomena which came about because of selective measures. For a simpler example, one could say that at some point in time a beneficial mutation arose which raised the relative fitness of the individual bearing it; as such, this trait eventually spread throughout this individual’s population. However, complex adaptations, which include isolating mechanisms, “usually are based not on single mutations, but on combinations of mutations that jointly or successively increase in frequency due to natural selection.”

[I]solating mechanisms are often behavioral: an individual wild animal that encounters individuals of its own species as well as of other species chooses [author's italics], overwhelmingly or solely, to mate with individuals of its own species. And yet, that animal, when caged with an individual of the other sex of another species, may interbreed freely and produce fertile hybrids. Thus, interfertility or hybridization of caged animals is not relevant to the definition of species. There are numerous examples of species that rarely or never hybridize with each other in the wild, but that do hybridize and produce fertile offspring if a male of one species and a female of another species are put together in a cage where no potential mate of their own species is available to them.

These observations lead us to the question why the enormous diversity of animals or plants in nature does not constitute a continuum of individuals, each of which is slightly different from other individuals, but is instead separated into discrete packages that do not interbreed with each other. Why are different gene pools packaged into reproductively isolated species? The inferiority of most hybrids provides the answer to this question. The populations of each species possess a well-balanced genotype that had been selected for this internal harmony by thousands of generations of selection. Hence hybridization with a different species of a very different genotype is likely to produce in the hybrids a deleterious recombination. It is the role of the species-specific isolating mechanisms to prevent such hybridization, or to reduce greatly its frequency.

One must remember that if observed over the course of time, there is no absolute, isolated point at which speciation occurs. Since the transition from subspecies to species between two similar populations occurs while they are often geographically isolated, the BSC holds that the two populations must be reintroduced to one another and mating must result in inviable or sterile hybrids. However, there are isolating mechanisms which evolve prior to speciation (see contention between the definitions of species and isolating mechanisms), which make mating between different populations of the same species the exception, rather than the rule. In such a case, sufficient evolutionary divergence has occurred between two populations of a single species to warrant their being called subspecies. It may be posited that the development of a number of ethno-cultural elements—usually thought of as being exclusive to humans—may be no more than the evolution of behavioral isolating mechanisms. (Granted, cultural transmission is a process of learning; however, the development of culture as such is a specific event in human evolution, and therefore must be understood as being a concrete occurrence in the context of natural history.) Language is the clearest example; it divides populations through the most fundamental of behaviors: communication. The evidence which shows correlations between linguistic and genetic differences is enough to reinforce such a conclusion.

Even with sufficient evidence to equate the demic or ethnic group with race, there exists a tendency among many preeminent biologists to conclude that race does not exist, primarily due to a predilection for naively associating race with skin color. Cavalli-Sforza, who has done a lifetime’s worth of tremendous work in the field, concluded that "the classification into races has proved to be a futile exercise." Futuyma has stated that “each supposed racial group can be subdivided into an indefinite number of distinct populations.” These scientists’ pessimism stems from the fact that their categorization of race is simply too broad. Consider that Futuyma has said that “morphologically similar peoples are not necessarily genetically most similar overall; for example, Philippine and Malay Negritos share some morphological features with Africans, but are genetically as distinct from them as are morphologically less similar populations,” while Cavalli-Sforza estimates a 26 percent admixture of “white” genes in the “black” population of the United States. They have completely lifted the notion of race from its geographic and environmental context. Invariably, evolutionary divergence will ensue when a population migrates to a new habitat. In order to thrive in a novel environment, a population will evolve, because only a select portion of the original population’s members will survive to reproduce. Therefore, a given race will inevitably change over time; and in zones of hybridization, nascent races are emerging—but this is not to say that they do not exist—for to do so is to deny natural history! Viewed over the course of time, what once was a distinct race or population group will have evolved into multiple new racial groups. Perhaps, interpreted differently, there is some degree of truth in Futuyma’s former statement after all, if one considers that evolution is a never-ending phenomenon. For indeed, there are no ends in life; all are processes.

NOTES
Ernst Mayr and Jared Diamond, The Birds of Northern Melanesia (New York: Oxford University Press, 2001), 120.
Robert J. Brooker, Genetics: Analysis and Principles (New York: Benjamin Cummings, 1999), 705.
Robert L. Smith and Thomas M. Smith, Ecology & Field Biology, 6th ed. (New York: Benjamin Cummings, 2001), 161.
Brooker, 705.
Smith, 365-6.
Douglass J. Futuyma, Evolutionary Biology, 3rd ed. (Sunderland, Massachusetts: Sinauer Associates, Inc.), 736.
Ibid., 741.
Ibid., 385.
Ibid., 739.
Ibid., 342.
Ibid., 31-2.
Ibid., 761.
Ibid., 280-1.
Ibid., 245.
Brooker, 697.
Ibid., 698.
Ibid., 711.
Futuyma, 737.
Ibid., 385.
Ibid.
Brooker, 705.
Futuyma, 457.
Ibid., 761.
Mayr, 120.
Ibid., 122.
L. Luca Cavalli-Sforza, Paolo Menozzi, Alberto Piazza, The History and Geography of Human Genes (Princeton, New Jersey: Princeton University Press, 1994), 19.
Futuyma, 737.
Ibid.