Subspecies and Classification

Subspecies and Classification
Smith, H., Chiszar, D., and Montanucci, R. 1997.  Herpetological Review 28(1):13-16

 


We regard species as genetically discrete (i.e., separate and independent) populational entities, whereas subspecies are taken as genetically non-discrete (confluent) populational entities. That distinction we regard as axiomatic despite arguments to the contrary (e.g., Barton and Hewitt 1985).

The non-discrete nature of subspecies is evident from their definition as geographic segments of any given gonochoristic (bisexually reproducing) species differing from each other to a reasonably practical degree (e.g., at least 70-75%), but to less than totality. All subspecies are allopatric (either dichopatric [with non-contiguous ranges] or parapatric [with contiguous ranges], except for cases of circular overlap with sympatry); sympatry is conclusive evidence (except for cases of circular overlap) of allospecificity (separate specific status). Parapatric subspecies interbreed and exhibit intergradation in contact zones, but such taxa maintain the required level of distinction in one or more characters outside of those zones. Dichopatric populations are regarded as subspecies if they fail to exhibit full differentiation (i.e., exhibit overlap in variation of their differentiae up to 25-30%), even in the absence of contact (overlap exceeding 25-30% does not qualify for taxonomic recognition of either dichopatric populations or of parapatric populations outside of their zones of intergradation). Phenotypic adjustment to differing environmental conditions through natural selection is likely the primary factor in divergence of parapatric subspecies, and undoubtedly is involved in some dichopaffic subspecies. The founder effect and genetic drift are involved more in the latter than in the former.

In spite of the objective validity of subspecies, they have been seriously questioned with increasing vigor for over 40 years, beginning most prominently with Wilson and Brown (1953; but see Wilson 1994). More serious threats have come in recent years from proponents of the newly propounded Phylogenetic and Evolutionary Species Concepts.

The inherent non-discrete nature of subspecies, combined with their long, justifiable history of acceptance as an essential part of biosystematics, has perforce been a problem in the context of phylogenetic inference that logically deals with discrete entities. The impasse has led to unjustified rationalizations in the form of either outright rejection of subspecies or of forcing them into a higher rank (species) for which they are fundamentally not qualified as here (and commonly) defined.

Proponents of the Evolutionary Species Concept dispose of subspecies, for the most part, by disregarding them completely as a component of the biotic classification system (Frost 1995; Frost et al. 1992; Simpson 1961; Wiley 1981, 1992; Wilson and Brown 1953). Typically, in the application of that concept, subspecies are examined critically for their distinctiveness, and those that do not rigorously qualify in that context are not accepted taxonomically.  By contrast, proponents of the Phylogenctic Species Concept have generally acted in concordance with the views espoused by Barton and Hewitt (1985), by elevating valid subspecies to species rank despite their non-discrete nature (Baum 1992; Cracraft 1992; Davis and Nixon 1992; Eldredge and Cracraft 1980, Nelson and Platnick 1981). Doing so leaves the term subspecies applicable only to minor geographic variation that usually would not be accepted as taxonomically significant, as, for example, clinal segments and pattern classes (e.g., Cracraft 1992:104). Were subspecies so relegated, we too would join Cracraft in rejecting them.

We hold that neither rationalization is justified or necessary. The rational policy is to continue to accept subspecies as a legitimate and essential part of biotic classification, but at the same time to exclude them from phylogenetic analyses that are logically limited to discrete, fully distinct entities. In that context, subspecies considerations cannot conflict in any way with species concepts and phylogenetic constructs based upon them. The subspecies category is already properly accommodated in the current edition of the International Code of Zoological Nomenclature, and its recognition, as in the past, is supported by biologists worldwide (Hawksworth et al. 1994).

The Rationale for Exclusion of Subspecies from the Phylogenetic Species Concept. — Current interpretation of phylogeny requires that, in phylogenctic classification, populations maintain evolutionary independence if they are to be recognized as taxonomically distinct units. Therefore, parapatric subspecies cannot be embraced in phylogenetic philosophy and practice because they have no phylogeny in the sense of a history of separate identity. On the contrary, dichopatric (= non-parapatric allopatric) populations may individually be regarded as full species, if sufficiently well differentiated (i.e., infallibly diagnosable, with fixed character differentiation), or, if not, as tertiary subspecies. Degrees of distinction (one or more characters) and the extent of intergradation differ widely in nature, and their interpretation in some cases inevitably results in subjective assessment of ranking that is equally inescapable in the application of any species concept. That fact is no argument against the validity of subspecies as nomenclatural entities, although it is a strong argument for excluding subspecies from phylogenctic analyses.

The Problems Created by Subspecific Exclusion from All Classification. — The emergence of a guiding phylogenetic (historical) philosophy in systematics was regarded by Frost et al. (1992:46) as “the biggest paradigm shift in systematics in the last 140 years.”

There is good reason for universal acceptance of the basic tenets of the Evolutionary or Phylogenetic species concepts in proper contexts. It is critical, however, to recognize that these contexts are not all-inclusive. The common perception of classification as conforming with and representing phylogenetic hypotheses must be superimposed upon the even more basic responsibility of reflecting biodiversity. Systematics and classification therefore have two functions, here referred to as taxonomic and phylogenetic. It is not sufficient that classification only reflect phylogeny; it must also reflect biodiversity by accounting for all “kinds” of animals, and subspecies as well as species constitute “kinds.”

The dual responsibility of classification to reflect both phylogeny and biodiversity has long been recognized (e.g., Simpson 1961:27-28). To limit the scope of these dual responsibilities of classification by exclusion of subspecies, through their distortion by elevation to species rank, or through abandonment, in order to reflect phylogeny at all classification levels, is unwarranted. Alternatively, having two classifications, one for each role (phylogenetic and biodiversal), would be chaotic.

Frost et al. (1992), in stating the case for Phylogenetic Classification, argued forcefully for abandonment of subspecies, and Frost later (1995) implemented his views in a novel way. So tempting has been that move toward simplicity that it has spawned widespread neglect of comprehensive studies of the geographic variation that often delineate subspecies. Thus two problems are constituted by subspecies in present contexts: their validity in the first place, and, if recognized at all, their integration within a phylogenetic system of classification.

Validity of Subspecies. — Despite arguments against admission of subspecies in taxonomy, that category has consistently proven useful and illuminating. Nevertheless, as pointed out by Frost et al. (1992), even such a staunch supporter as Mayr on occasion (1982) wrote deprecatingly about the nature and value of the subspecies category. In a more recent work, Mayr and Ashlock (1991:4 1) noted that “some of the best proofs of the occurrence of evolution have emerged from the study of polytypic species taxa. To convert the nominal species of all groups of animals into well- delimited polytypic species taxa is therefore one of the major tasks of taxonomy.” Nevertheless, they (ibid.:53) remarked that the “new systematics” of today recognizes “the subspecies as a category, not as an evolutionary unit.”

It is perfectly true that subspecies are not independent evolutionary units, as previously noted in the context of phylogenetic systematics. But, it is equally true that they are products of evolution and, where valid, are recognizably different taxonomic entities. To exclude valid taxonomic entities from classification misrepresents fact and neglects a level at which a major part of evolution is occurring at all times and at varying rates, although it is little studied, understood, and appreciated in most groups of animals. Such studies, however, “have provided the best available evidence for the process of allopatric speciation, the frequent origin of evolutionary novelties in peripherally isolated populations, and numerous intermediate stages in the evolutionary process, thus elucidating previously inexplicable discontinuities” (Mayr and Ashlock 1991:41).

The initial and most enduringly influential opponents of subspecies were Wilson and Brown (1953), who argued that “it is more informative to focus on the traits and not on the subspecies that might be concocted from them” (Wilson 1994:208). But, by 1994, Wilson (loc. cit.) later confessed that “Some populations can be defined clearly with sets of genetic traits that do change in a concordant, not a discordant manner. Furthermore, the subspecies category is often a convenient shorthand for alluding to important populations even when their genetic status is ambiguous.”

Indeed, perhaps the most powerful argument against the validity of subspecies is that intraspecific geographic variation commonly involves several or more characters varying independently either kaleidoscopically or discordantly, in part due to selection pressures differing with each environmental variable. It is nevertheless true that consistent (at the 70% level or better) recognizability of subspecies is evident within some species. Occasionally only one character qualifies, but usually a suite is involved. In multivariate contexts, subspecies are definable by the suite of characters that explains the largest adequate percentage of the variance of the data-set, thus minimizing the “noise” produced by the variance of other characters. Hence the spectre of an infinite number of subspecies is in reality a delusion. Blanket rejection of subspecies, even on the basis of deficient or defective analysis, denies their possible, if not proven, validity, under the criteria here stated, as consistently recognizable geographic entities. Altertively, elevation of them to full species rank denies their non-discrete nature. Neither alternative is justified.

Although defense of subspecies has been dismissed by some phylogeneticists as old-fashioned and outmoded, the fact remains that comprehensive and objective studies of geographic variation, especially in widely distributed (but also some narrowly distributed) species, often reveals the presence of distinctive geographic segments that eminently qualify for taxonomic, even if not phylogenetic, recognition (e.g., Grismer et al. 1994; Taylor et al. 1994). Rejection of subspecies on grounds of phylogenetic incompetence, or difficulty of analysis, or of burdensome museum administration, is spurious and fails to recognize fact. We view the current popularity of disregarding subspecies as an uncritical attitude.

Rejection of subspecies as non-genetic ecotypes unless proved to be genetic adaptations is unwarranted, inasmuch as dichopatric species of any closely knit species group are subject to the same uncertainty. Parsimony dictates acceptance that allopatric populations that are phenotypically distinguishable at a taxonomic level have their differences genetically based unless or until proved otherwise.

Rejection of the subspecies concept inevitably leads in many instances to unjustified elevation to species rank of taxa that should rank as subspecies. Careful consideration of rank alternatives for different allopatric populations is severely discouraged if one of those alternatives no longer exists.

Although the subspecies category has on occasion been abused in the past, the same is true of the species and every other nomenclatural category. Abuses particularly exist where populations are subject to predominantly discordant geographic variation or linear clinal variation, when segments are nevertheless recognized taxonomically. A comprehensive (rather than piecemeal) study of geographic variation within the species should precede the delineation and naming of subspecies, or should be the ultimate test of subspecies that have been erected piecemeal. The use of multivariate statistical procedures can provide approaches that are reasonably objective and not dependent on preconceptions about taxonomic membership. Nonetheless, the discriminatory power of such methods depends critically on the quality of the characters being analyzed and, in addition, the adopted standard for level of differentiation required for taxonomic recognition. Multivariate analyses (Thorpe 1987) are useful techniques for substantiation of subspecific validity, with revival of the now generally neglected 75% (or similar) rule (idem:7).

The conclusion most emphatically is that subspecies, even on strictly theoretical grounds, are a vital component of taxonomic practice, should be retained as an acceptable option where warranted, merit inclusion in classification, and are properly accommodated in current rules of nomenclature. They are of importance not only in systematics but also in other theoretical disciplines such as biogeography and evolution itself.

In addition, from a practical point of view and quite apart from theoretical validity, the subspecies category is vital to balanced conservational, medical, nutritional, and other applied biologies. In such considerations, the recognition of geographical segments, particularly of widely distributed species, is of fundamental importance because they may represent differentiated gene pools that can be substantially different in important ways (e.g., Glenn and Straight 1985, 1987). Although the focus of phylogenetic systematics is properly on the established directions of genetic change, it would be tragic if that focus were allowed to lead to the abandonment of studies of intraspecific geographic variation that are of such vital importance in the understanding, assessment, and conservation of biodiversity.

In that context, Ryder (1986) proposed recognition of “evolutionarily significant units” (ESU), alternatively “evolutionarily significant populations” (ESP), where they exist among the subspecies of any given species. That concept was endorsed and expanded by Vane-Wright et al. (1991) and Vogler and DeSalle (1993), although the terms ESU and ESP, as applied by these authors, are inappropriate and misleading, as noted by Cracraft (1991); in reality they were dealing with “conservationally” significant units (“CSU”). Nevertheless the focus by these authors upon subspecies and their relative merit for conservation was thoroughly justified. Unfortunately, Cracraft (op. cit.), observing that in his opinion all ESU’s are phylogenctic species, concluded that “Under this concept, subspecies have no special ontological [i.e., incipient species] status and can be abandoned.”

As an example of the importance of subspecies in conservational considerations, Sceloporus undulatus garmani, an arenicolous, terrestrial, cursorial, striped subspecies with reduced semeions (ventral color patches) appears to have become extinct, or nearly so, in parts of its range on the plains of eastern Colorado. On the contrary, another, very different, larger, cross-barred subspecies with well-developed semeions, S. u. erythrocheilus, remains common on the eastern slopes of the Rocky Mountain foothills, where it leads a scansorial life on trees and, mostly, rocks. The two subspecies occur within a few kilometers of each other in some areas, but no intergradation occurs and even gross sympatry is possible. Different conservational measures may be required for these two subspecies, but they would be difficult or impossible to prescribe or implement if no subspecies were recognized. Entire subspecies populations could become extinct if attention were directed to the species as a whole, which could be regarded as basically healthy. In cases such as this, elevating the constituent subspecies to species rank does not always provide a solution. For example, in the case cited, there is a complete, although stepped, continuity between the two taxa: S. u. garmani intergrades to the south with S. u. consobrinus, the latter with S. u. tristichus to the west, and that in turn with S. u. erythrocheilus to the north – a typical circular approximation of range, if not overlap.

Although the practical constraints of conservation efforts may require restriction of attention to the species rank, elevation of subspecies as here and as commonly defined to species rank would be a disservice to limited conservational efforts aimed at preservation only of major genetic resources.

In defending the concept of subspecies, i.e., maintaining them in classification much as in the past, we do not see them as of universal existence among organisms. In many groups they appear never to have evolved, no doubt for various reasons, including extreme vagility. We merely insist that in some groups they are readily evident, and that where this is the case, they merit taxonomic recognition, serving as they do as vehicles for the development of testable hypotheses regarding the causes, proximate and ultimate, for variation and its geographic stabilization.

Integration With Phylogenetic Classification. — The second problem posed by recognition of subspecies in the era of phylogenetic emphasis is perhaps of relatively minor concern, since it can be resolved by context and requires no operational modification of long-established custom. Where the context and goals are strictly phylogenetic, subspecies obviously should be disregarded. Where the context and goals are taxonomic to the lowest level, subspecies should be recognized, as they have been over the past few decades. They are entities already incorporated into taxonomic and nomenclatural procedure, as indicated by the present edition of the International Code of Zoological Nomenclature and its predecessors as early as the 1905 Regles. Biologists worldwide also reiterate their intent to maintain recognition of subspecies in the future (Hawksworth et al., 1994). The studies by Grismer et al. (1994) and Reichling (1994) demonstrate the compatibility of subspecies with phylogenetic systematics. There is no conflict, hence no need for exploration of alternative nomenclatural systems.

Intraspecific Taxonomic Derivation. — In the context of Phylogenetic Classification, as currently interpreted, “intraspecific phylogeny” approaches an oxymoron, and in effect has been widely so interpreted in recent discourses. Yet derivational patterns are commonly discernible among the subspecies of polytypic species, as noted by Thorpe (1987:3), who commented that intraspecific “patterns of geographic variation can [italics ours] be caused by both current ecological conditions and historical factors, i.e. phylogenesis.” The evolutionary phenomena culminating with at- tainment of species rank are also involved in patterns of subspeciation. However, we suggest that intraspecific evolutionary patterns evident among subspecies be designated as taxogenetic (taxon-forming), rather than phylogenctic (derivational), in order to avoid what might be regarded as an oxymoronic application of the latter term.

Indeed, Olmstead’s (1995) proposal for distinguishing “apospecies” (with one or more uniquely derived characters) and “plesiospecies” (with a unique combination of characters, none derived) can logically be extended to subspecies. Thus, “aposubspecies” (e.g., Sceloporus undulatus erythrocheilus with unique lip/throat reddish coloration; S. u. belli, with fused gular semeions) can be distinguished from “plesiosubspecies” (e.g., most other subspecies of S. undulatus).

Summary. — The nature and evolutionary implications of biodiversity is a central challenge of modern biology. To appreciate the full extent and significance of biodiversity, we assuredly need to recognize and have names for the discrete, unquestionably phylogenetically competent taxa belonging to the categories of species, genera, families, etc. We need also to recognize and have names for the non-discrete but genetically distinctive geographic segments of species, even if they are regarded as phylogenetically incompetent (i.e., derivationally non-committal). Both concerns are essential to analyses of diversity. It perforce follows that to pursue such analyses properly a comprehensive and unified system of nomenclature is essential. Our system must include all these groups, both discrete and non-discrete.

Subspecific nomenclature is more than a step in the study of natural variation. It is a tool for conveying information about major patterns of variation within species, flagging opportunities for causal analyses. A subspecies name draws attention to a geographic segment of a species that in some way is recognizably different, and beyond that, it provides information about diversity to a variety of disciplines from genetics and ecology to conservation biology. The study of intraspecific variation could go on without the use of subspecific nomenclature, but a tremendous lot of biotic diversity would be obscured and made almost inaccessible by the absence of names. Workers will fail to notice biological diversity without names.

LITERATURE CITED

BARTON, N. H., and G. M. HEWITT. 1985. Analysis of hybrid zones. Ann. Rev. Ecol. Syst. 16:113-148, figs. 1-4.
BAUM, D. 1992. Phylogenetic species concepts. Trends Ecol. Evol. 7:1-2.
CRACRAFT, J. 1991. Systematics, species concepts, and conservation biology.  Abstracts Soc. Cons. Biol., 5th Ann. Mtg., Univ. Wisconsin-Madison: 79.
CRACRAFT, J. 1992. Species concepts and speciation analysis. In M. Ereshefsky (ed.), The Units of Evolution: Essays on the Nature of Species, pp. 93- 100. Massachusetts Inst. Tech., Cambridge. xviii, 405 pp.
DAVIS, J. I., and K. C. NIXON. 1992. Populations, genetic variation, and the delimitation of phylogenetic species. Syst. Zool. 41(4):421-435.
ELDREDGE, N., and J. CRACRAFT. 1980. Phylogenetic Patterns and the Evolutionary Process. Columbia Univ. Press, New York.
FROST, D. R. 1995. Foreword to the 1995 printing. In H. M. Smith, Handbook of Lizards (reprint), pp. xvii-xxv. Comstock, Ithaca, New York.
FROST, D. R., A. G. KLUGE, and D. M. HILLIS. 1992. Species in contemporary herpetology: comments on phylogenetic inference and taxonomy. Herpetol. Rev. 23(2):46-54.
GLENN, J. L., and R. C. STRAIGHT. 1985. Distributions of proteins similar to Mojave toxin among species of Crotalus and Sistrurus. Toxicon 23:28.
GLENN, J. L., and R. C. STRAIGHT. 1987. Variation in the venom of Crotalus lepidus klauberi. Toxicon 25:142.
GRISMER, L. L., H. OTA, and S. TANAKA. 1994. Phylogeny, classification and biogeography of Goniurosaurus kuraiwae (Squamata: Eublepharidae) from the Ryukyu Archipelago, Japan, with description of a new subspecies. Zool. Sci. 1 1:319-335.
HAWKSWORTH, D. L., J. McNEILL, P. H. A. SNEATH, R. P. TREHANE, and P. K. TUBBS. 1994. Towards a harmonized bionomenclature for life on earth. Biol. Intern., Special Issue (30):1-45.
E. MAYR. 1982. Of what use are subspecies? Auk 99:593-595.
E. MAYR and P. D. ASHLOCK. 199 1. Principles of Systematic Zoology. Second edition. McGraw-Hill, New York. xvi, 475 pp.
NELSON, G., and N. PLATNICK. 1981. Systematics and Biogeography: Cladistics and Vicariance. Columbia Univ. Press, New York. xiii + 567 pp.
OLMSTEAD, R. G. 1995. Species concepts and plesiomorphic species. Syst. Bot. 20(4):623-630.
REICHLING, S. B. 1994. The taxonomic status of the Louisiana pine snake (Pituophis melanoleucus ruthveni) and its relevance to the evolutionary species concept. J. Herpetol. 29(2):186-198.
RYDER, 0. A. 1986. Species conservation and systematics: the dilemma of subspecies. Trends Ecol. Evol. l(l):9-10. SIMPSON, G. G. 1961. Principles of Animal Taxonomy. Columbia Univ. Press, New York. xiii, 247 pp.
TAYLOR, H. L., C. BEYER, L. HARRIS, and H. PHAM. 1994. Subspecific relationships in the teiid lizard Cnemidophorus tigris in Southwestern Arizona. J. Herpetol. 28(2):247-253.
THORPE, R. S. 1987. Geographic variation: a synthesis of cause, data, pattern and congruence in relation to subspecies, multivariate analysis and phylogenesis. Boll. Zool. 54:3-1 1.
VANE-WRIGHT, R. I., C. J. HUMPHRIES, and P. H. WILLIAMS. 1991. What to protect? Systematics and the agony of choice. Biol. Cons. 55:235-254.
VOGLER, A. P., and R. DESALLE. 1993. Diagnosing units of conservation management. Cons. Biol. 8(2):354-363. WILEY, E. R. 1981. Phylogenetics: The Theory and Practice of Phylogenetic Systematics. Wiley, New York. xv, 439 pp.
WILEY, E. R., 1992. The evolutionary species concept reconsidered. In M. Ereshefsky (ed.), The Units of Evolution: Essays on the Nature of Species, pp. 79-92. Massachusetts Inst. Tech., Cambridge.
WILSON, E. 0. 1994. Naturalist. Island Press, Washington, D.C. xii, 380 pp.
WILSON, E. O., and W. L. BROWN. 1953. The subspecies concept and its taxonomic application. Syst. Zool. 2(3):97-111.

Figure 4 from The Race FAQ by John Goodrum

Fig. 4. From Nei, M. and Roychoudhury, A. 1993. Evolutionary Relationships of Human Populations on a Global Scale.  Molecular Biology and Evolution 10(5):927-943.

Fig. 5.  From Bowcock. A.M., Ruiz-Linares, A., Tomfohrde, J., Minch, E., Kidd, J.R., Cavalli-Sforza, L.L. 1994. High resolution of human evolutionary trees with polymorphic microsatellites. Nature 368:455-457.

Figure 2 from The Race FAQ by John Goodrum

Fig. 2.  From Barbujani, G., Magagni, A., Minch, E., Cavalli-Sforza, L.L. 1997. An apportionment of human DNA diversity. Proceedings of the National Academy of Sciences 94: 4516–4519.

Fig. 3.  From Jorde, L.B., Watkins, W.S., Bamshad, M.J., Dixon, M.E., Ricker, C.E., Seielstad, M.T., Batzer, M A. 2000. The Distribution of Human Genetic Diversity: A Comparison of Mitochondrial, Autosomal, and Y-Chromosome Data. American Journal of Human Genetics 66:979–988.

The Race Frequently Asked Questions (F.A.Q.) by John Goodrum

The Race FAQ

by John Goodrum

Do biological races exist within the human species?  If scientific terms are to be used consistently, this question can only be answered in the broader context of non-human taxonomy.  The intent of this paper is to investigate what constitutes a race (or subspecies) in other species, and to answer some questions concerning whether the traditional human races might qualify.


Q: What is the definition of ‘race’ or ‘subspecies?’

The terms ‘race’ and ‘subspecies’ are most often used synonymously [1,2] although the former is normally used when talking about human populations. When a distinction is made, ‘race’ generally implies a lower level of differentiation, but because this term is not commonly used in the recent non-human literature, ‘race’ and ‘subspecies’ are used interchangeably throughout this paper.

Much of the debate over the existence of human races stems from how one chooses to define ‘race’ (or ‘subspecies’).  No realistic definition can avoid using qualitative terms, yet these invariably invite disagreement in their application: “a group of individuals in a species showing closer genetic relationships within the group than to members of other such groups”[3]; “essentially discontinuous sets of individuals”[4];  “conspecific populations that differ from each other morphologically”[5];  “genetically non-discrete (confluent) populational entities”[6];  “geographically circumscribed, genetically differentiated populations”[7]; or groups identified “by the usual criterion that most individuals of such populations can be allocated correctly by inspection.”[8] Compounding the confusion, still others employ the term ‘race’ in a way more akin to ‘species’ than to ‘subspecies.’[9]

In response to questionable interpretations of the U.S. Endangered Species Act, and to help ensure the evolutionary significance of populations deemed ‘subspecies,’ a set of criteria was outlined in the early 1990s by John C. Avise, R. Martin Ball, Jr.[10], Stephen J.  O’Brien and Ernst Mayr [11] which is as follows: “members of a subspecies would share a unique, geographic locale, a set of phylogenetically concordant phenotypic characters, and a unique natural history relative to other subdivisions of the species.  Although subspecies are not reproductively isolated, they will normally be allopatric and exhibit recognizable phylogenetic partitioning.”  Furthermore, “evidence for phylogenetic distinction must normally come from the concordant distributions of multiple, independent genetically based traits.”[12]  This is known as the phylogeographic subspecies definition, and a review of recent conservation literature will show that these principles have gained wide acceptance.

A number of studies have employed this subspecies definition, and these can be helpful in inferring how the definition is applied in practice.  A good example is a paper entitled “Phylogeographic subspecies recognition in leopards (Panthera pardus): Molecular Genetic Variation,”[13]  co-authored by Stephen J. O’Brien (one of the definition’s co-authors).  From the ranges of the revised leopard subspecies (Fig. 1) we can infer that a ‘unique geographic locale’ does not require that a range be an island, or share no environmental characteristics with another.  Rather, it merely requires a subspecies to have a geographical association as opposed to a subset of individuals sharing a trait but drawn from different geographical populations.  Conversely, two subspecies will not remain distinct if they occupy the same locale over evolutionary time.  Hypothetical human races have been proposed in which members would share a single trait (e.g., lactose tolerance or fingerprint pattern)[14]  but not a common geographic locale.  These ‘races,’ therefore, would not be valid under the phylogeographic definition.

Whether a population has had a unique natural history can be inferred from its degree of differentiation with respect to other such populations.  The arbitrary division of an interbreeding, genetically unstructured group will result in subgroups that are genetically indistinguishable, whereas populations that evolve more or less independently for some length of time will accumulate genetic differences (divergent gene frequencies, private alleles, etc.) such that they “exhibit recognizable phylogenetic partitioning.”

A set of “phylogenetically concordant phenotypic characters” is taken to mean several morphological, behavioral or other expressed traits that tend to co-vary within, but differ among, putative subspecies.  This indicates that members of the group have evolved together relative to other groups, and may reflect shared demography, local adaptation, sexual selection or other evolutionary effects.

The need for “concordant distributions of multiple, independent genetically based traits” requires us to recognize that too much inference from a single trait or single genetic locus is unwarranted.  For instance, rather than indicating recent co-ancestry, a trait shared by two populations might have evolved independently in response to some environmental variable, while the potential idiosyncrasies of any single gene can limit its reliability to paint an accurate phylogenetic picture.  Most population genetics theory relies on loci that have evolved neutrally (i.e., in the absence of natural selection) so a non-neutral locus may give misleading results.  The best way to avoid this potential source of error is to examine a large number of independently-evolving loci.


Q: How genetically diverse are humans?

It’s become a popular view that the human species is extraordinarily homogeneous genetically when compared to most other species.[15]  This notion argues against the existence of human races, because very little genetic variation within the entire species means there cannot be much variation between major human populations.  Before examining this further, we should first inquire about what is meant by ‘genetic diversity.’

Because little can be learned from a locus that is the same in every individual, the study of phylogenetics depends on polymorphic loci.  Over the past few decades, methods have been developed that allow different kinds of these polymorphic ‘markers’ to be assayed in individuals.  Prior to the 1990s, genetic diversity was usually inferred from classical (non-DNA) polymorphisms, such as blood groups, serum proteins, allozymes and immunoglobins.  Later, restriction enzymes were employed to produce a useful class of marker at the DNA level, restriction fragment length polymorphisms (RFLPs).  Other loci such as mitochondrial DNA (mtDNA), Alu insertions, minisatellites, single nucleotide polymorphisms (SNPs) and microsatellites (STRPs – short tandem repeat polymorphisms) have also been utilized for population genetic studies.  Due to their high polymorphism, rapid mutation rate and random distribution throughout the genome, microsatellites are probably the most important class of marker in use today.[16]  Highly variable loci are an advantage in phylogenetics because they can provide the finer resolution necessary for distinguishing closely related populations (such as subspecies).

The majority of  population genetic studies over the past decade have investigated the various regions of mitochondrial DNA, a molecule that resides in the cytoplasm outside a cell’s nucleus.  mtDNA contains 37 genes and is comprised of 16,569 base pairs in humans.  Because it is haploid and maternally inherited, mtDNA has an effective population size about one-quarter that of the autosomes (the non-sex chromosomes).  It’s easy to collect, has a relatively high mutation rate, and in particular, its lack of recombination allows for a straightforward assessment of the relationship between haplotypes.  Lack of recombination also means that all parts of the molecule are completely linked, which prevents independent evolution of mtDNA’s 37 genes and non-coding control region.  For this reason, mtDNA is considered a single genetic locus for phylogenetic purposes.  Humans have relatively low mitochondrial diversity compared to the other great apes, and reports of this are mostly responsible for the belief that humans have low genetic diversity.  However, mtDNA makes up just a few millionths of the human genome,[17] and as a single locus, carries little statistical weight.

When allele frequency data are used to estimate genetic diversity within a population, a frequently reported statistic is the average number of alleles per locus (A), but because rare alleles do not contribute much to overall diversity, the most informative statistic is average heterozygosity (H).  This is estimated from both the number of alleles and the frequencies at which they occur, and is generally defined as the percentage of individuals in a population that are heterozygous (have two different alleles) at a random locus.  In general, genetic diversity is synonymous with mean heterozygosity.

Table 1.  Comparative figures for the genetic diversity of humans and a variety of other large mammals (sampled across much or all of their range except as noted), based on autosomal microsatellites (He and Ho = expected and observed heterozygosity, respectively):


Species                                                 He                    Ho

Humans [18]                                         --                    0.776
Humans [19]                                         --                    0.70-0.76
Humans [20]                                         --                    0.588-0.807
Chimpanzees [21]                                0.78                 0.73
Chimpanzees [22]                                 --                    0.630
African buffalo [23]                             0.759                0.729
Leopards [24]                                     0.36-0.80            --
Jaguars [25]                                        0.739                   --
Polar bears [26]                                  0.68                     --
Brown bears (N. America) [27]          0.26-0.76          0.30-0.79
Brown bears (Scandinavia) [28]          0.709                 0.665
Canada lynx [29]                                   --                    0.66
Bighorn sheep [30]                             0.681                 0.566
Coyote [31]                                       0.675                 0.583
Gray wolf (N. America) [32]              0.620                 0.528
Pumas [33]                                            --                   0.52
Bonobos [34]                                     0.59                   0.48
Dogs (42 breeds) [35]                        0.616                 0.401
African wild dogs [36]                        0.643                    --
Australian dingo [37]                          0.47                   0.42
Wolverines (N. America) [38]            0.42-0.68              --
Wolverines (Scandinavia) [39]              --                     0.27-0.38
Elk (North America) [40]                   0.26-0.53              --

In addition to microsatellites, a 2001 study [41] reviewed the literature on protein variation for 321 mammal species and reported mean expected heterozygosity of 5.1%.  In comparison, Takahata (1995) reports an unbiased estimate of protein heterozygosity in humans of 10-14%.[42]  Also, Nei’s 1987 text Molecular Evolutionary Genetics gives an estimate of mean heterozygosity for classical protein polymorphisms of 0.148 in humans, and has this to say about the general level of genetic diversity in other organisms:

“In the last two decades, the extent of protein polymorphism has been studied for numerous organisms ranging from microorganisms to mammals by using electrophoresis.  In most of these studies, the extent was measured by average gene diversity or heterozygosity.  In early days, the estimate of heterozygosity was based on a small number of loci, so that its reliability was low.  In recent years, however, most authors are examining a fairly large number of loci (20 loci or more).Average heterozygosity or gene diversity varies from organism to organism. In general, vertebrates tend to show a lower heterozygosity than invertebrates. If we consider only those species in which 20 more loci are studied, H is generally lower than 0.1 in vertebrates and rarely exceeds 0.15.  In invertebrates, a large fraction of species again show an average heterozygosity lower than 0.1, but there are many species showing a value between 0.1 and 0.4.  In plants, the number of loci studied is generally very small, so that the estimates are not very reliable. However, if we consider only those species in which 20 or more loci are studied, the average heterozygosity is generally lower than 0.15 except in Oenothera, where permanent heterozygosity is enforced by chromosomal translocations (Levin 1975; Nevo 1978; Hamrick et al. 1979; Nevo et al. 1984). The highest level of gene diversity so far observed is that of bacteria (H=0.48 based on 20 loci in Escherichia coli, Selander and Levin 1980; H = 0.49 based on 29 loci in Klebsiella oxytoca, Howard et al. 1985).” [43]

Obviously, humans are not at the low end of the genetic diversity spectrum, particularly in relation to other mammals.

We might wonder how humans could have accumulated so much genetic diversity when we are such an evolutionarily ‘young’ species, but this assumes that the human species arose by an extreme founding event – a time at which the entire species’ diversity resided in just a few individuals – and that all humans today are descended from those few founders.  This supposed event is often conflated with the concept of “mitochondrial Eve,” a woman who lived roughly 200,000 years ago and is the most recent common ancestor of all human mtDNA.  This conflation is incorrect, however, because the coalescence of mtDNA to a single ancestor back in time does not imply a demographic bottleneck, but is expected even in a population of constant size.[44]  Avise (2001) has noted that in a hypothetical population with 15,000 breeding females (about three times the long-term human estimate), reasonable variances in reproductive success would likely see mtDNA coalesce to a single founding lineage in 300,000 years (~15,000 human generations), without any change in population size.[45]  Thus, the coalescence time of human mtDNA doesn’t necessarily have anything to do with a population bottleneck or speciation event, but rather is more or less a function of long-term effective population size, with a large standard error.[46]  Variants of nuclear autosomal genes, having a four-fold greater effective population size than mtDNA, generally coalesce in the neighborhood of 800,000 years ago.[47] This indicates that a substantial amount of our existing genetic variation originated in the population ancestral to modern humans.

In sharp contrast to the shallow genealogy of human mtDNA, some alleles of the major histocompatibility complex appear to coalesce over 30 million years ago, long before the emergence of the hominid lineage.[48,49]  Some MHC genes are known to have over two hundred alleles,[50] maintained by balancing selection at loci where heterozygosity confers some fitness advantage.  Several researchers have demonstrated that humans retain too much ancestral MHC diversity for a severe bottleneck to have ever occurred during human evolution.[51-53]  There’s fairly wide agreement that the long-term effective population size of humans has been roughly 10,000,[54] making it unlikely that the sum total of our genetic diversity has ever resided in fewer than several thousand individuals.

Additionally, the genetic profile of humans is much different from that of other large mammals that are believed to have experienced a recent demographic bottleneck.  The cheetah, for example, is thought to have had a severe population contraction sometime during the late Pleistocene.  While cheetahs apparently have had time to accumulate a moderate amount of variation at some rapidly evolving loci, current populations display very little allozyme or MHC variability.[55] Another example is the moose.  Old World and New World subspecies are estimated to have diverged at least 120,000 years ago, but sometime before divergence a bottleneck must have occurred that reduced both allozyme and MHC diversity to a fraction of that found in humans.[56]


Q: Haven’t human populations been separated for too short a time for distinct races to have evolved?

Although there is some evidence of non-African archaic contributions to the modern gene pool,[57] it appears likely that current human populations derive largely from a single African population, and diverged something less than 150,000 years ago.  While time of separation is important in evolutionary divergence, effective population size can be an equally important factor.[58] While the overall size of the human species has probably never been reduced to a handful of individuals, populations that migrated out of Africa may well have remained relatively small for thousands of years before beginning to expand toward their current numbers.[59,60] If so, divergence due to random genetic drift would have occurred rapidly in the absence of high gene flow.[61]

An example of this has been observed in a North American elk herd re-established from a small number of founders.  Between 1915 and 1924, 34 animals from two large herds in the western U.S. were released in north-central Pennsylvania.  The herd remained at about this size for 50 years and now numbers about 550.  Very low microsatellite heterozygosity (0.222) and very large genetic distance from the source populations (pairwise FST = ~0.45) now characterize this herd.[62]

It has also been proposed (originally by Darwin) that sexual selection (mate choice) may promote the retention of physical features in populations long after neutral genetic variation has been replaced by gene flow, and that this might help explain the prominent morphological variation among human groups.[63]

At any rate, divergence times for major subdivisions within the human species, while relatively shallow, are certainly not unique when compared to subdivisions within many other mammal species.  An appendix to Avise et al. (1998)[64] lists eleven mammal species with major phylogroups that diverged between 100,000 and 500,000 years ago, based on mtDNA sequence divergence.  Being a single genetic locus, mtDNA is subject to selection effects and a large amount of random variation, so these times are probably not terribly reliable.  For example, mtDNA has indicated 2-3 million years of isolation between western and eastern gorilla subspecies in Africa, but a recent study of multiple nuclear loci provided little support for that time depth.[65]  A related situation exists in chimpanzee taxonomy, particularly with regard to the distinctiveness of the eastern (P.t. schweinfurthii) and western equatorial (P.t. troglodytes) subspecies.  Studies utilizing nuclear loci,[66,67] as well as more thorough sampling of mtDNA, are calling into question earlier mtDNA results that indicated long separation.  As some of these chimp researchers point out, “The current volatile state of chimpanzee molecular taxonomy is largely due to the fact that studies to date have relied heavily on only a handful of genetic loci.”[68]

 


Q: Isn’t there actually more genetic distance between populations within the traditional human races than between the major races themselves?

In 1972, Richard Lewontin studied global variation at seventeen protein polymorphisms,[69]  and found that about 85% of genetic variation existed between individuals within a given population.  The next largest portion, about 8%, was found between populations within continents, with the remaining 6% of variance  attributable to differences between the major human races (Fig. 2).  The ~85% within-population figure has been affirmed numerous times, while the relative size of the other components of variance probably depends on the specific populations chosen for analysis, and is often the reverse of Lewontin’s findings.  In any event, many data sets have been assembled since 1972 for classical polymorphisms and all other genetic markers, and as a general rule, populations within continents are more closely related to one another than they are to the populations of other continents.  This pattern can be seen in any matrix of global genetic distances, such as those assembled by Cavalli-Sforza et al. in The History and Geography of Human Genes.

Population genetic studies often report AMOVA statistics (Analysis of MOlecular VAriance), which show the hierarchical proportions of variance between aggregates of the individuals sampled.  The following is a discussion of worldwide data on autosomal microsatellites and RFLPs, Alu insertions, mtDNA and Y chromosome STRPs:

“The hierarchical AMOVA analysis shows that, with the exception of Y STRPs, all systems show much less differentiation between populations within continents than between continents. This result is expected when there is greater gene flow between populations that are in close geographic proximity to one another. The autosomal values…are especially small, ranging from 1.3% for the RSPs to 1.8% for the Alu polymorphisms. This is in agreement with the small continental GST values shown in table 4…they are highly consistent both with one another and with previous analyses of worldwide variation in autosomal microsatellites and RFLPs, which also show considerably greater differentiation between continents than between populations within continents… The fact that there is little differentiation between populations within continents has important implications in the forensic setting, in that it supports the current practice of grouping reference populations into broad ethnic categories when autosomal STRP data are used…” [73] (Fig. 3)


Q: How genetically differentiated are human continental populations (the major races) from one another compared to populations of other species?

Before the advent of conservation biology and modern phylogenetics, subspecies were normally delineated by morphological characteristics.  The “seventy-five percent rule” goes back to 1949, stating that subspecies classification is merited if at least 75% of individuals can be correctly assigned to their group by inspection.[74] This rule isn’t in common use today, but the importance of genetically-based morphological differences is still apparent in many recent phylogenetic studies.  Some biologists argue that a 70 or 75 percent rule should still be a standard criterion in taxonomy, as applied to individuals outside of hybrid zones where the ranges of subspecies overlap.[75]

On the basis of morphology, we can compare the traditional human races (as well as some minor races) to chimpanzee subspecies.  Individuals of the former can be correctly assigned at much greater than 75% accuracy,[76]  while the latter are morphologically indistinct, and difficult or impossible to classify when raised in captivity.[77,78]

Of course, the domestic dog demonstrates that morphological difference doesn’t necessarily correlate with underlying genetic difference, so let’s look at population differentiation from a genetic perspective.  Many measures of divergence or ‘genetic distance’ are in use today, the most common being FST, originally developed by the late population geneticist Sewall Wright.  FST is a statistic that describes the proportion of variance within a species that is due to population subdivision. It can be estimated in a variety of ways (e.g., by AMOVA [79] or theta [80]), but the general expression is FST = (Ht-Hs)/Ht where Ht is the genetic diversity within the total population, and Hs the average diversity within subpopulations.  Its value can be considered inversely proportional to gene flow, or indicative of the length of time two populations have been evolving separately, and may vary according to which locus or family of loci are under study.  As mentioned earlier, haploid loci like mtDNA and the NRY have effective population sizes one quarter that of autosomal loci, making them much more sensitive to drift and thus to the effect of population subdivision.  Other types of loci have their own unique evolutionary characteristics, so we need to remember that an FST value based on one class of loci may or may not be representative of the overall evolutionary distinctiveness of the populations in question. For these reasons, values based on several types of loci should be considered before drawing any firm conclusions.

Keeping the preceding caveats in mind, these are qualitative guidelines suggested by Sewall Wright for interpreting FST:

“The range 0 to 0.05 may be considered as indicating little genetic differentiation.
The range 0.05 to 0.15 indicates moderate genetic differentiation.
The range 0.15 to 0.25 indicates great genetic differentiation.
Values of FST above 0.25 indicate very great genetic differentiation.” [81]

Table 2.
Here are some comparative figures for humans and other species (again, sampled across most or all of their ranges except as noted), based on autosomal microsatellites:

Species                                                         FST


Gray wolves (North America) [82]                    0.168
Pumas [83]                                                       0.167 (mean pairwise)
Humans (14 populations) [84]                           0.155 (AMOVA)
Asian dogs (11 breeds) [85]                              0.154
European wildcats (Italy) [86]                           0.13
Humans (44 populations) [87]                           0.121 (AMOVA)
Coyotes (North America) [88]                          0.107
Wolverines (North America) [89]                      0.067 (mean pairwise)
Jaguars [90]                                                      0.065
African buffalo [91]                                           0.059
Polar bears [92]                                                0.041 (mean pairwise)
Canada lynx [93]                                              0.033
Humpback whales [94]                                    0.026 (mean pairwise)

Additionally, Uphyrkina et al. (2001) employed mtDNA and microsatellites to identify nine leopard subspecies by our phylogeographic criteria.  Unfortunately for the sake of comparison, the authors reported microsatellite RST rather than FST values.  RST is an FST analogue, but their values can be quite different numerically.  However, if the RST/FST ratio for leopards is similar to those of other felids [95,96]  the maximum reported RST value of 0.363 would correspond roughly to an FST of 0.14-0.15, very similar to the human value at microsatellite loci.  The mean proportion of private (population-specific) microsatellite alleles for the nine revised leopard subspecies was found to be 6.3%, compared to a mean value of 7.1% for three major human continental populations [97] while the mean Nei’s genetic distance DS for allozymes between the leopard subspecies identified by Miththapala et al. (1996) is 0.019 (range 0.002-0.047) [98] and can be compared to the protein distances between three major human races (mean 0.037; range 0.028-0.048). [99]

Wolverines, polar bears, Canada lynx and humpback whales have not traditionally been divided into subspecies, while two or more subspecies (or ‘breeds’ in the case of the Asian dogs) have been named in all of the remaining non-human species listed above.  The overall FST value for African buffalo is not particularly large, but the mean value of 0.095 between the central African population and other populations was considered large enough to support their traditional subspecies status.  Based on cranial morphology and geography, 24 subspecies of the gray wolf in North America were reduced to five in 1995, while North American coyotes are considered to have eastern and western subspecies.

For our purposes, the studies of population structure in the big cats are especially informative, since these used phylogeographic criteria to suggest possible taxonomic revision.  Jaguars have traditionally been divided into eight subspecies, but Eizirik et al. (2001) considered the population structure too weak (FST = 0.065) to warrant naming any.  In contrast, distinct phylogroups were readily apparent within both pumas and leopards, although somewhat fewer than classically described (6 vs. 32 in pumas, and 8 or 9 vs. 27 in leopards).

It should be noted that high phenotypic diversity in some domestic animals (such as the Asian dogs) is mostly the result of selective breeding for quantitative traits, rather than the long-term allopatry or local adaptation that leads to morphological distinctiveness in “natural” populations.  As expected, the average microsatellite distance between these dog breeds as measured by Nei’s genetic distance DA (0.194) [100] is correspondingly smaller than the average distance between fourteen human populations (0.322). [101]

Human FST values of 12-15% are typical not just for microsatellites, but also for classical protein polymorphisms,[102] autosomal RFLPs[103] and Alu insertions.[104]   Values for mitochondrial DNA and the Y chromosome are substantially higher.  It would seem, then, that the level of genetic differentiation among human populations is not especially small, and in fact is entirely adequate for race designation, particularly when coupled with consistent morphological differences.

 


Q: Which human populations qualify as major races?

The construction of reliable evolutionary trees involves a number of technical issues, such as sampling design, mutation mechanisms, genetic distance measures and particularly, tree-building algorithms.  Nonetheless, the topology of human trees (Figs. 4, 5) is remarkably consistent regardless of which class of loci are considered, and principal component analysis of genetic data also produces predictable clustering (Fig. 6).  Either method gives a good visual overview of the general relatedness of the world’s populations.

By analysis of classical markers, Nei & Roychoudhury (1993) identified five major human clades:  sub-Saharan Africans, Caucasians, Greater Asians, Australopapuans and Amerindians.  Evolutionary trees constructed with autosomal RFLPs,[105] microsatellites[106] and Alu insertions[107] show similar topology.  Frequently, Amerindians are grouped together with Asians, indicating four major clades, and it has been suggested that this should be a minimum.[108] Obviously, additional structure exists within each of these groups, but as we’ve seen, it’s generally weak compared to the differentiation among the ones listed here.  For this reason alone, the term ‘race’ applies well to these major groupings.

In terms of our phylogeographic definition, each of the major human clades has a geographical association (slightly less clear today than 500 years ago, but only slightly); each has a distinguishing set of phenotypic traits; phylogenetic partitioning is apparent and consistent at multiple genetic loci; and substantial intergroup genetic distances (i.e., FST) indicate unique natural histories on an evolutionary timescale.

The criticism can be made that the placement of some populations located between the “cores zone” of these major races (e.g., Europe or East Asia) is ambiguous.  However, in non-human taxonomy this would not normally invalidate the subspecies status of well-differentiated core populations.[109,110]  In fact, zones of intergradation have traditionally been taken as evidence that core groups are indeed subspecies rather than different species.[111] While some clinal variation in the genetic traits of subspecies is generally the rule, human variation tends to show extensive zones where clinal gradients are relatively flat, separated by short zones of steeper gradient.  This pattern can be seen on the dust jacket illustration of The History and Geography of Human Genes.

 


In conclusion…

Some will find provocative the idea that humans display a subspecies-like population structure, but given that the major human subdivisions revealed by modern genetics had already been recognized as early as 1775,[112] it shouldn’t be as provocative as the alternative notion, i.e., that human races don’t exist.

So if we do belong to different biological races, what, if anything, does this mean?  Subspecies are closely related by definition, and human races appear to be less genetically distant than the major phylogroups of many other species.[113]  While FST values for neutral variation are by no means negligible from a population genetics point of view, it’s significant that the overwhelming majority of genetic variation is found within populations, reaffirming the importance of treating people as individuals.  It’s also significant that the FST value for the most prominent racial trait – skin color – has been estimated to be about 0.60,[114] which means that the visible variation between races greatly exaggerates overall genetic differences.  Admixture in some populations further clouds the picture.  The average European contribution to the gene pool of American blacks has been found to be about 20%,[115] and admixture between the major races in some other regions is substantially higher.

Nevertheless, when the taxonomic term is used consistently across species, it’s difficult to see any justification for the common assertion that human races are merely ‘social constructs.’  The motivation behind the assertion is a positive one, but denying biological realities at the outset is unlikely to lead to productive social dialogue on coping with human differences.

 


 


Supplement
FST Follies

In 1998, American Anthropologist published a paper by Alan Templeton entitled “Human Races – A Genetic and Evolutionary Perspective” [116] which seems to have had broad influence on the race question within anthropology and the social sciences.  In the first section of the paper, Templeton cites a 1997 article from Herpetological Review entitled “Subspecies and Classification.”[117]  Templeton asserts that, according to this paper, an FST value of .25 or .30 between populations is a “standard criterion” for subspecies classification.  He then provides a graph showing FST (or FST analogue) values for humans and 12 other species of large mammals (Fig. 7).  (The human value of 0.156 is from a 1997 paper, “An Apportionment of Human DNA Diversity”[118]  in Proceedings of the National Academy of Sciences.)  Two of the non-human values listed are lower than that for humans, but the other ten values are substantially higher, and appear to support Templeton’s claim that human populations are only weakly differentiated.

There are several curious things about this.  First, there is little, if any, corroboration in the recent literature for an FST value of .25 or .30 being a standard criterion for subspecies designation.  Secondly, if you actually read the paper by Smith et al., they never mention anything about FST values.  Rather, they say that “overlap [of differentiae] exceeding 25-30% does not qualify for taxonomic recognition of either dichopatric populations or parapatric populations outside of their zones of intergradation.”  What the authors are referring to here is not an FST value, but simply the long-standing 75 (or 70) percent rule discussed earlier.[119]  Templeton’s misinterpretation is all the more obvious when you consider that this subspecies rule and FST have an inverse relationship, i.e., a 75 percent rule implies greater differentiation than does a 70 percent rule, whereas an FST value of 0.25 indicates lesser differentiation than does a value of 0.30.  Additionally, FST is generally used to assess neutral genetic variation in these kinds of studies, which, as we’ve seen, can be quite different from expressed morphological variation.

The most interesting thing, however, about Templeton’s FST comparison is the fact that he uses a human value (0.156) based on autosomal loci (microsatellites and RFLPs), while nine of the ten largest non-human values, including the eight highest, are based on mitochondrial DNA.  This is quite misleading, because FST values for mtDNA are expected to be much higher than autosomal values.[120,121] The primary mechanism causing populations to diverge is usually genetic drift, and the magnitude of the effects of drift is inversely proportional to population size, as shown by Bodmer and Cavalli-Sforza (1976) through computer simulations (reproduced in Ref. 17, p.14).  The four-fold greater effective population size of autosomal loci vs. mtDNA virtually ensures that FST values based on the latter will be substantially greater than values based on the former, and in fact this is nearly always observed in population studies.  Since mtDNA is maternally inherited, sex-biased dispersal can also play a role in elevating FST for species in which males disperse over greater distances than do females.

In the present paper, every attempt has been made to use comparable data.

———————
Some typical comparative FST values for autosomal and mitochondrial loci, respectively, for similar or identical samples:

     Jaguar[122]                     0.065 vs. 0.295
Puma [123]                     0.167 vs. 0.467
Gray wolf [124,125]        0.168 vs. 0.76

 



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The citation for this paper is:

Goodrum, J.  The Race FAQ. July 2002. http://www.goodrumj.com/RaceFaq.html (located online at http://web.archive.org/web/20110711111007/http://www.goodrumj.com/RFaqHTML.html)

The Race FAQ by John Goodrum(PDF, 197kb)

Global suicide

Our human tendency is to externalize threats, so that we can contain them in a symbol or finite and tangible enemy.

This is a denial response to the more complex underlying reality, which is that most threats to us come from our own undisciplined and illogical behavior.

We want to blame hierarchy and authority for our problems if we can, but hierarchy and authority always exist, and emerge even after we get rid of them through anarchistic revolution.

Similarly, we want to blame carbon monoxide for the environmental holocaust we are creating. However, our ecocidal damage is not limited to carbon or climate change.

It’s not carbon levels rising that is killing off rare species. It’s not carbon levels rising that’s depleting fishing stocks. It’s not carbon levels rising that made our forests unable to soak up extra carbon.

Instead, using our Occam’s razor approach, we should look at what is most likely to be the environmental problem of any species reaching maturity on any planet: overpopulation, and the over-consumption of land it entails.

This is not a problem we can externalize. It is inherent to the growth of any civilization, no matter what species. Resources are finite and exploiting too many of them crowds out other life.

External threats are comforting because they are out of our hands. There is nothing we can do, except destroy them when they become troublesome.

Internal threats are within our control, but are also pitfalls based on common perceptual errors. For example, we overeat, or gamble away our money, or become addicted to drugs/drink and sex.

Any population can face a number of internal threats. It can grow too big; it can become unstable; it can poison itself with bad hygiene, or throw itself into instability with delusions.

It’s the growing too big that is finally being recognized:

Human numbers have risen from one billion to our current population of seven billion in 200 years. That is pretty short order, and we have got to that state through our cleverness and inventiveness. But that cleverness and inventiveness are now the sources of all the global problems we face today – and those problems are only going to intensify as our numbers continue to grow. It is really important to talk about overpopulation. Far too many scientists still refuse to discuss the issue. Yet it lies at the heart of all our environmental problems today.

…Our problems are not just those concerned with carbon emissions. There are so many other things – overfishing, destroying habitats and eradicating species – that we need to change. It is either that or sit and do nothing which, in effect, is the position we have adopted so far. Science has spent far too long hiding behind caveats. We have to come off the shelf although I suspect it may too late now.

With population rise comes another problem: we like to cover things in concrete. We want cars, so we create many more roads and parking lots. These are of a modern type which is completely covered, and reflects heat back into the atmosphere; it also prevents rainwater from being absorbed or groundwater from reaching the surface to evaporate.

Global concreting is a phenomenon that happens almost invisibly. A town finally discovers an industry, and grows. More people move in. More roads, more parking lots, more storage spaces and factories, hospitals, schools, prisons, etc. arrive.

What these do is effectively divide up the remaining natural and semi-natural land (backyards, gardens) into tiny bits. These bits confine plants and animals, because around them is high risk. They also concentrate both resources and waste.

The result is both a breakdown of the natural order that uses water exchange to cool itself, and the creation of very effective reflectors of light and insulators of heat within the earth itself.

Anecdotal evidence suggests that whenever an area gets “built up” and concreted, the climate changes for the warmer and drier.

Global concreting is an internal threat because how do we oppose it? Each of those concrete slabs is making some human being’s life better. There are dreams in those stores, restaurants, hospitals, etc.

As once source points out, if our population doesn’t grow, the economy stalls. If we stop expanding, and pouring more concrete, the whole house of Ponzi cards comes crashing down.

That’s your retirement fund that will become worthless.

The end result of this typical debacle is consumption of nature and its replacement with humans. This is also the cause of all of our environmental problems. If we left enough natural land, earth would regulate itself, absorbing our poisons and balancing resources.

But we press on like maniacs, denying the internal roots of our problem while perpetuating it with an almost demonic intensity.

This is at its root a war on beauty. We, humans, fear the world outside of the human. Other humans make us feel like there is some kind of significance, meaning or importance to our lives. That makes us feel better about powerlessness and death.

However, that view is threatened. Nature is not only lawless, but disinterested. We can die in the forest without the act having any more significance than ants eating an avocado. That knowledge makes us resentful of nature.

In our weird human way, we want the world to be human like us, and both under our control and affirming our important. Since nature does not do this, we wage war on it, hoping to completely replace it so that only our voices and judgments are heard.

With that imaginary external threat, we also kill a unique beauty. With it dies the hope that someone might wander deep in a forest, be lost in its majesty, and replace their concerns about death and powerlessness with a sense of awe and appreciation.

Global concreting

The foes of sensible environmental policy want you to believe that there is a binary question to conservation. Yes, you believe in global warming; no, you’re a denier — there are no other options. Either you’re good or you’re not.

Many people are suspicious of global warming because it’s one of those-easily abused catch-all concepts like “Jesus told me to do this” or “the Revolution demands this, comrade!” We instinctively do not trust the great ideological crusade. That’s sort of throwing the baby out with the bathwater, since some ideological crusades are presumably worth undertaking. That is, if we assume there are ideologies based on consequences in reality and not wishful thinking (“morality”).

As is fitting in a time of liberal politics, based in liberal democracy and with even our conservatives cementing their ideas with liberal goals, global warming is used to justify the liberal crusade for global redistribution of wealth. The liberals themselves don’t believe it, but because their ideology is based on personal satisfaction through socialization, and not results in reality, they don’t care. It sounds good and brings everyone together.

This of course puts humanity in a terrible place: as far as our public discourse goes, a very important issue has been tied to a divisive ideology. There is no way to win here except to give in to the liberal side, which half the population will not do. That in turn gives the other half a chance to act like Jesus On the Cross as they lament the ignorance of “the others.”

As a result, to put it mildly, the debate on global warming is poisoned, and it was poisoned by the left. There is nowhere to go with this issue now except to ignore it until the end. Caught in the middle are those of us who think something weird may be going on with the climate, but that global warming is not an accurate description.

What else could be to blame?

Land cover changes that alter the reflection of sunlight from land surfaces (albedo) are another major driver of global climate change. The precise contribution of this effect to global climate change remains a controversial but growing concern. The impact of albedo changes on regional and local climates is also an active area of research, especially changes in climate in response to changes in cover by dense vegetation and built structures. These changes alter surface heat balance not only by changing surface albedo, but also by altering evaporative heat transfer caused by evapotranspiration from vegetation (highest in closed canopy forest), and by changes in surface roughness, which alter heat transfer between the relatively stagnant layer of air at Earth’s surface (the boundary layer) and the troposphere. An example of this is the warmer temperatures observed within urban areas versus rural areas, known as the urban heat island effect. – Eo-Earth

As said around these parts before, global warming is convenient because it groups all of humanity’s destructive effects on the environment into a single measure, which is carbon output. This allows us to ignore other forms of pollution and the uglier fact that no land without a human touch can be found anymore. Even more importantly, land that is truly undeveloped is getting rarer and rarer.

Environmentalists from a more sensible time would wave away global warming as a detail. They would point to the simple fact that humanity has an exponential growth curve. Everywhere we go, we take over all useful land and divide it up into little parcels. We fence those in, cut off the natural species, and then cover the rest with concrete.

The result is many dysfunctions at once converging on a larger dysfunction. Natural ecosystems are shattered, removing their replenishing function. There are fewer trees to transform CO2 into oxygen. Rainfall is not retained, but becomes runoff, depleting the soil and poisoning the water with too many nutrients. Finally, the concrete which covers the whole mess tends to reflect heat and water while preventing anything from growing where it is.

Overpopulation, land overuse and industrial construction are the missing elements that humanity is trying to hide behind global warming. Cutting carbon allows these bigger problems to continue, which may be why we want global warming so badly to be the culprit. Slashing carbon will crimp our lifestyles, but facing overpopulation requires we make some hard moral decisions that no one wants to face.

The most revealing part of this situation is that our environmental sins come from the same root as all our other sins. We are dominating by social factors, like how our ideas appear to the judging minds of others, or how popular our solutions are. Complex and difficult thoughts will never be as popular as a harmless scapegoat that allows people to avoid any real change. And so the circus bleats on.

Appeal

Oftentimes one hears it whispered that we live in an age of appearance rather than substance. An age of what seems to be, rather than what is. An era when impression weighs heavier than content. Something catches our eye; we glimpse at it for a brief moment. Perhaps we let the thing slide through our fingers before putting it back on the stack and leaving it be. We move on, elsewhere.

To many, that is what the Postmodern era –- or rather, living within the Postmodern era –- feels like. We lack the time and clarity of mind to focus upon a thing; there is always the next thing to do, the next place to be. We have to do with snippets of information; we are too much in a hurry to put the pieces of the puzzle together. The picture of the greater whole escapes us, and we accept this because we are busy.

And sometimes we are driven by a quest for meaning to glimpse past the part of the puzzle to comprehend the greater whole. The greater whole is not formed of parts, but the relationship between those parts, and from the interaction and interconnections between them, a greater structure and order emerges. One such glimpse is a fleeting vision of the value of culture.

Cultural awareness is more valuable and important than a dismissive attitude toward other races or cultures. There is some moral difficulty in being proud of the acts of our ancestors, in the sense that there is no point in being proud of something over which one totally has no influence. It’s the same thing as being moody when a certain football team loses a match. If we feel pride over what our ancestors did, must we also be ashamed of — for example — the slave trade?

Yet, and this is more important, we need cultural awareness if we are to make sense of the country in which we live. Of the rules and customs, for example. As a student once said to me: “People laugh about an aboriginal wearing a penis-tube, but if you ask him why he’s wearing that penis tube, he will tell you a story. Western people today won’t be able to tell you anything about what they wear other than; ‘it’s fashion’ or; ‘it’s my taste’.”

We can take our ancestors and their actions as models. Of what we aspire to be, and of what we do not aspire to be. When the Roman historian Livy described the actions of Romulus, he did not intend his reader to blindly revere and imitate the founder or Rome. Instead, he wanted his reader to look at Romulus’ actions, to study the circumstances under which those actions took place, and to make his own conclusions about that conduct as a matter of learning.

Those who stumble on the value of culture feel something rumbling within their minds. They feel the weight of a dying society, and the choking futility it creates. They seek escape in an artistic muse, in an age of aristocratic elegance. An age where girls could be girls and boys could grow up to be men. And everywhere around us glimmered golden-yellow and green, everything rocked and shone, caressed by the fresh breeze of spring and accompanied by orchestrated music.

Those who resist modernity are fed up with a decadent and aimless age, so they invent new symbolism from summaries of the past. They mold together Teutonic knights, the genius inventors of the industrial age, proud castles, innocent maidens and idyllic towns. They forge a ‘utopia’ from ranks of disciplined and confident soldiers, exquisite dining rooms, majestic architecture and craftsmanship.

And this is what our leaders and representatives must do in a fractured and shattered age. In this age, cognitive learning is vastly undervalued, and as such the iron logic of facts hardly makes an impression on anyone safe a few. Our leaders and representatives must learn to speak a language of images, of painting a beautiful landscape that seduces both listener and viewer. Not until art has won the heart of the audience reason and logic can captivate its mind.

The Immune System

Friedrich Wilhelm Nietzsche cannot be described as a traditional philosopher.  He consistently returns to the the theme of health, he refers to himself as a cultural physician, and he famously wrote, “my genius is in my nostrils.”

He may be referring to how in everyday life we are predominantly conscious of the divide between true and false, and less aware of the divide between healthy and sick. Some would say this occurred because we have taken our more primitive functions for granted and fallen in love with our brains instead, forgetting the wisdom of our other organs.

The metaphor of the immune system will help explain this. When a disease invades the body, the immune system is not at all obliged to accept the disease at face value — in other words, to accept the “truth” of the disease.  If it did, it would be a pretty shoddy immune system. 

In a sense, the function of the immune system could be described as irrational. The immune system clashes with disease in a war for power. Each fights for the ultimate prize: more life! The immune system cannot wait for the brain to make a decision. It must be constantly xenophobic and warlike.

The immune system does not operate on the level of true/false. The same is true at the cultural level.  We are too in touch with our brains, and not enough with our immune system and our nostrils. Training our brains to become comfortable with cultural ruin is not a solution; it is a rationalization.

Avoiding rationalization requires we embrace the irrational. Our cultural antibodies must irrationally fight the disease without appeal to the brain. Today we are reliant on medicine in both a literal sense, and a metaphorical one. Like a patient who becomes accustoms to antibiotics, and thus loses the ability to fight disease without them, our rationalization of the status quo on a cultural level has weakened us.

Imagine three different tribes. Tribe A has superior intelligence, medicine and technology. Tribe B has superior spirit, religion and willpower. Suppose that these two tribes are warring with each other.  Tribe A uses medicine and technology to heal its sick and wounded at all costs. Tribe B shuns medicine and instead puts its faith entirely in the will of the universe to heal its sick and wounded. Clearly, Tribe A will crush Tribe B, and perhaps only a very few of exceptional health from Tribe B will survive.

But out of the mist comes Tribe C! Tribe C uses medicine only in emergencies and otherwise puts its faith in the will of the universe. They believe that the strong will survive with or without medicine. Perhaps in the short term Tribe A will get the better of Tribe C thanks to their superior technology and medicine. But it’s not at all hard to imagine that in the long run,  Tribe C will emerge victorious. The literal and metaphorical immune system of Tribe A will become dependent on medicine, while the literal and metaphorical immune system of Tribe C will remain robust thanks to nature.

There is nothing moral or immoral about a disease invading a body.  The disease does what it does.  But by the same token, the immune system does what it does. It is no different when a native culture resists and rejects foreign ideas and influence. It has nothing to do with morality nor does it have anything to do with what is “true” or “false.” 

The antibody is as irrational as the disease, and as single-minded. The question is not about true and false, but a will to power and the will to life. We should not fight or justify our own irrational cultural impulses. We should integrate them. They like our immune systems ensure a long and healthy life.