Richard C Lewontin

The Apportionment of Human Diversity

It has always been obvious that organisms vary, even to those pre-Darwinian idealists who saw most individual variation as distorted shadows of an ideal. It has been equally apparent, even to those post-Darwinians for whom variation between individuals is the central fact of evolutionary dynamics, that variation is nodal, that individuals fall in clusters in the space of phenotypic description, and that those clusters, which we call demes, or races, or species, are the outcome of an evolutionary process acting on the individual variation. What has changed during the evolution of scientific thought, and is still changing, is our perception of the relative importance and extent of intragroup as opposed to intergroup variation. These changes have been in part a reflection of the uncovering of new biological facts, but only in part. They have also reflected general sociopolitical biases derived from human social experience and carried over into “scientific” realms. I have discussed elsewhere (Lewontin, 1968) long-term trends in evolutionary doctrine as a reflection of long-term changes in socioeconomic relations, but even in the present era of Darwinism there is considerable diversity of opinion about the amount or importance of intragroup variation as opposed to the variation between races and species. Muller, for example (1950), maintained that for sexually reproducing species, man in particular, there was very little genetic variation within populations and that most men were homozygous for wild-type genes at virtually all their loci.

PERSPECTIVE:EVOLUTION AND DETECTION OF GENETIC ROBUSTNESS

Abstract Robustness is the invariance of phenotypes in the face of perturbation. The robustness of phenotypes appears at various levels of biological organization, including gene expression, protein folding, metabolic flux, physiological homeostasis, development, and even organismal fitness. The mechanisms underlying robustness are diverse, ranging from thermodynamic stability at the RNA and protein level to behavior at the organismal level. Phenotypes can be robust either against heritable perturbations (e.g., mutations) or nonheritable perturbations (e.g., the weather). Here we primarily focus on the first kind of robustness—genetic robustness—and survey three growing avenues of research: (1) measuring genetic robustness in nature and in the laboratory; (2) understanding the evolution of genetic robustness; and (3) exploring the implications of genetic robustness for future evolution.

Evolution and the theory of games

Abstract The shortcomings of present population genetic theory are discussed as they pertain to problems of speciation, extinction and the evolution of genetic systems. It is suggested that the modern theory of games may be useful in finding exact answers to problems of evolution not covered by the theory of population genetics. An outline of relevant topics in the theory of games is given. It is suggested that the most pertinent utility measure for a population is its one-generation probability of survival and that a strategy or a mixture of strategies corresponding to a maximin strategy will be found in natural populations. These notions are applied to a population segregating for two alleles with different norms of reaction in different environments. For the model chosen the optimal strategy is found to be homozygosis for different alleles in different populations due either to inbreeding or genetic isolation. A segregating polymorphism in such populations would be a detriment to the species, although the heterozygotes are more constant in fitness.

THE EFFECTS OF POPULATION DENSITY AND COMPOSITION ON VIABILITY IN DROSOPHILA MELANOGASTER

The ability of organisms of a given genotype, relative to that of other genotypes, to transmit their genes to future generations has been shown repeatedly to be a function of the environment in which these organisms develop and reproduce. This ability, the adaptive value of the genotype, may vary markedly from one environment to another or may be quite uniform under a wide variety of environmental circumstances. A striking illustration of this can be found in the work of Dobzhansky and Spassky (1944). These authors investigated the viability, from egg to adult, of a number of genotypes isolated from natural populations of Drosophila pseudoobscura, when the larvae were raised at three different temperatures. While some genotypes showed no difference in larval survival frotm one temperature to another, others showed distinct differences. Thus, one genotype, although lethal at 25.50C., showed a nearly normal larval survival at 16.50 C. The dependence of the adaptive value of a genotype on the environment should extend to biotic as well as physical factors of the ecology. Indeed, a large portion of ecological research has been devoted to studies on the interrelation of species as well as on the effect of varying population densities within a species. The relative abundance of a species is dependent upon the kind and abundance of other species around it. Moreover, the abundance of a given species at one stage of its life cycle is a function, and often not a simple function, of its abund-

THE ROBUSTNESS OF HOMOGENEITY TESTS IN 2 X N TABLES.

SUMMARY A Monte Carlo investigation of 2 X n tables with fixed marginals has been performed. The results of the Monte Carlo distribution show that the probability of Type I error given by the conventional x2 test is in general conservative for 5 or more degrees of freedom even when expectations of successes are very small in each

THE GOODNESS-OF-FIT TEST FOR DETECTING NATURAL SELECTION IN RANDOM MATING POPULATIONS

Suppose, now, that a sample is taken from such a population and that the three genotypes are distinguishable. There will be three observed frequencies, nl, ns and ns, but only two independent observations since there is the linear restriction The issue has recently been raised in the pages of this journal and elsewhere as to the possibility of judging the relative fitnesses of genotypes from the frequencies of these genotypes in populations. Wallace (1958) has provided several numerical examples where severe selection pressures do not result in appreciable deviations of the observed zygotic frequencies from expectation under Hardy-Weinberg equilibrium. Novitski and Dempster (1958) attempted by means of a digital computer to estimate the adaptive values of genotypes in Drosophila melanogaster using only the observed genotypic frequencies. They found that the computer produced an infinite variety of best fit values for the fitnesses. We are indebted to them for first calling our attention to this problem and to Dr. Bruce Wallace for urging us to publish our findings. If the frequency of an allele B in a population is p and that of its alternate allele b ia q = 1 p, then following random mating but before any natural selection has occurred the zygotes will be in the relative frequencies

Does Culture Evolve

The drive to describe cultural history as an evolutionary process has two sources. One from within social theory is part of the impetus to convert social studies into “social sciences” providing them with the status accorded to the natural sciences. The other comes from within biology and biological anthropology in the belief that the theory of evolution must be universal in its application to all functions of all living organisms. The social--scientific theory of cultura evolution is pre-Darwinian, employing a developmental model of unfolding characterized by intrinsic directionality, by definable stages that succeed each other, and by some criterion of progress. It is arbitrary in its definitions of progress, and has had the political problem that a diachronic claim of cultural progress implies a synchronic differential valuation of present-day cultures. The biological scheme creates an isomorphism between the Darwinian mechanism of evolution and cultural history, postulating rules of cultural “mutation,” cultural inheritance and some mechanism of natural selection among cultural alternatives. It uses simplistic ad hoc notions of individual acculturation and of the differential survival and reproduction of cultural elements. It is unclear what useful work is done by substituting the metaphor of evolution for history.

The mystery of language evolution

Understanding the evolution of language requires evidence regarding origins and processes that led to change. In the last 40 years, there has been an explosion of research on this problem as well as a sense that considerable progress has been made. We argue instead that the richness of ideas is accompanied by a poverty of evidence, with essentially no explanation of how and why our linguistic computations and representations evolved. We show that, to date, (1) studies of nonhuman animals provide virtually no relevant parallels to human linguistic communication, and none to the underlying biological capacity; (2) the fossil and archaeological evidence does not inform our understanding of the computations and representations of our earliest ancestors, leaving details of origins and selective pressure unresolved; (3) our understanding of the genetics of language is so impoverished that there is little hope of connecting genes to linguistic processes any time soon; (4) all modeling attempts have made unfounded assumptions, and have provided no empirical tests, thus leaving any insights into languages origins unverifiable. Based on the current state of evidence, we submit that the most fundamental questions about the origins and evolution of our linguistic capacity remain as mysterious as ever, with considerable uncertainty about the discovery of either relevant or conclusive evidence that can adjudicate among the many open hypotheses. We conclude by presenting some suggestions about possible paths forward.

Dialectics and Reductionism in Ecology

The philosophical debates which have accompanied the development of science have often been expressed in terms of dichotomous choices between opposing viewpoints about the structure of nature, the explanation of natural processes, and the appropriate methods for research:

Race: A genetic melting-pot

Ancestral genetic data are far more useful for medical purposes than are racial categories, which may be correlated with disease for social or economic rather than biological reasons.