A Defense of Gene-Centrism

Which came first, the chicken or the egg? Given the non-essential nature of evolutionary biology this question really has no uniquely true answer. Consider a similar question: Which is the primary unit in natural selection, the chicken or the egg? This, roughly speaking, is the difference between the organism centrists (the chicken) and the gene centrists (the egg). The former says that eggs (genes) are what chickens use to make more chickens. The latter says that chickens are what eggs use to make more eggs. In this post we will consider the gene-centrist’s primary argument for why their view is the uniquely true one.

C. Kenneth Waters argues, as we saw in a recent post, that neither the egg’s-eye-view nor the chicken’s-eye-view is uniquely true to the exclusion of the other. Just as velocity is a concept which only makes sense after a frame of reference has been established, so too selective forces only make sense after a unit of selection has already been established. To continue the parallel, just as the inexistence of any absolute frame of reference in physics does not make all relative frames of reference of equal pragmatic value, so too the inexistence of any absolute or true unit of selection does not make all units of selection equally useful for the purposes at hand. Waters fully acknowledges this.

This, however, does not seem to do justice to the powerful arguments which the gene-centrists present against the phenotype or the group as being possible units of selection. The reason why the gene must be the level at which natural selection operates is not merely due to the pragmatic value of such a frame of reference. Rather, argues the gene-centrist, the gene’s-eye-view is the uniquely true one for the simple fact that the gene is the only unit which meets the necessary prerequisites in order for natural selection to function at all.

In his book The Selfish Gene, Richard Dawkins repeats and elaborates upon a number of arguments produced by George Williams for the gene-centered view of evolution. Let us consider first the reasons why the former holds that groups (populations) and phenotypes cannot be seen as the units of selection. Briefly, populations are not discreet enough entities in that they lose their identity by constant blending. Phenotypes, on the other hand, are each unique thereby failing to provide the stability necessary for natural selection to have any effect. In short, both the phenotype and the group are too ephemeral.

In contrast, genes have three features which no other units have:

1. Longevity in the form of copies of themselves.

2. This longevity is accomplished by way of replicative fidelity.

3. They also have fecundity in producing numerous copies of themselves.

Dawkins takes these conditions to be absolutely necessary given the nature of natural selection. Charles Darwin, it will be remembered, held that variation, heritability and a struggle for survival were together necessary and sufficient for natural selection to produce adaptive change. This, however, is not entirely true as Darwin himself acknowledged to some degree. What natural selection requires is a significant degree of stability in the unit of selection in that the rate of variation must be comparably slow compared to the rate of heritable reproduction in order for selective pressures to have any sustained effect. As Williams put it,

“The essence of the genetical theory of natural selection is a statistical bias in the relative rates of survival of alternatives (genes, individuals, etc.). The effectiveness of such bias in producing adaptation is contingent on the maintenance of certain quantitative relationships among the operative forces. One necessary condition is that the selected entity must have a high degree of permanence and a low rate of endogenous change, relative to the degree of bias (differences in selective coefficients). Permanence implies reproduction with a potential geometric increase.”

This stability is accomplished, Williams and Dawkins argue, only by genes in the form of their making highly accurate copies of themselves within populations and throughout generations. Indeed, Williams defines a gene as “any hereditary information for which there is a favorable or unfavorable selection bias equal to several or many times its rate of endogenous change.”

Notice that the gene centrist does not merely argue that phenotypes and populations do not have a high degree of evolutionary fitness. Rather, they argue that phenotypes and populations do not meet the necessary criteria to have evolutionary fitness in any meaningful sense of the word. Evolutionary fitness is a trait which only sufficiently stable replicating entities have and neither phenotypes nor populations are such things. The term “evolutionary fitness” no more applies to them than it does to clouds in the sky.

Thus, the only entities which can have any kind of evolutionary fitness are replicators with a high degree of fidelity, fecundity and longevity. These constraints eliminate all other potential units of selection (species, groups, phenotypes, traits, cells and possibly even gene-complexes), leaving the gene’s-eye-view as the only viable and therefore true option.

There are two responses which the relativist can provide to such an argument. First, one can argue that what matters in terms of replication is not fidelity in physical replication but rather fidelity is functional replication, loosely defined. Thus, a daughter can be seen as a father’s way of eventually creating more fathers some times down the line. A second response would be to simply deny any essential role to replication whatsoever. Population dynamics only cares about the frequency of any type within a population, regardless of how this frequency increases or decreases. These responses will be pursued in greater detail in future posts.