Evolution for Everyone

Individualism according to Williams’ Principle is dead but another version of individualism is also part of George’s legacy. At the time, no one fully appreciated that the two versions are different and incompatible with each other. Some things are only obvious in retrospect.

The second version has its roots in the arcane details of population genetics theory. The typical population genetics model posits genes for traits that are expressed in individuals. In a diploid single locus model, a given gene (A) exists in two genotypes (Aa and AA). In a polyploid or multi-locus model, the number of genotypes that include a given gene becomes even larger. A given genotype might always have a single fitness value of many fitness values, depending upon the details of the physical and social environment. All of these genotypic and environmental contexts with fitness consequences nudge the frequency of the gene up or down in the total population. Their combined effect is called the “average effect” , which is like the bottom line of an accounting ledger that reflects all deposits and withdrawals. No matter how complex the details of a population genetics model, a comparison of average effects tells us which genes will increase in frequency in the total population, all things considered.

George wrote about average effects in Adaptation and Natural Selection, where he aptly called it a bookkeeping method. George also noted that genes have a special status as units of high-fidelity replication lacking in both individuals and groups. All of this made genes appear like “the fundamental unit of selection”, an idea that is associated with Richard Dawkins and his book The Selfish Gene, but which began with Adaptation and Natural Selection (as Dawkins is careful to acknowledge).

All well and good, but how does it concern group selection and levels of adaptation? There are two renderings and neither one holds any comfort for individualism. First, all group selection models based on genetic evolution (as opposed to cultural evolution) are population genetics models with the same basic structure as other population genetics models. Genes code for traits that have fitness consequences based on a variety of contexts. In the case of group selection models, the contexts include the existence of multiple groups, the genetic composition of the groups, and the fitness differentials within and among groups. All of this is duly entered into the ledger, resulting in the bottom line of average effects, which determine which gene evolves all things considered. To say that a gene evolves because it has the highest average effect is no argument at all against group selection. When a trait evolves by group selection according to Williams’ principle, group selection is the evolutionary force that causes the genes coding for the trait to have the highest average effect (see my previous post titled “na├»ve gene selectionism” for more).

Second, let’s suppose that there was an argument for calling the gene the fundamental unit of selection. In that case, individual organisms would fail to quality, along with groups. Either way, there is no warrant for individualism, which is the claim that adaptations reside exclusively at the level of individual organisms.

These points might seem obvious today, but for decades the concept of genes as “the fundamental unit of selection” was treated as a drop-dead argument against group selection and somehow supportive of “the theory of individual selection.” Richard Dawkins is still confused or otherwise in denial. In my opinion, George shared in the confusion. When good scholars of evolutionary thought comb through his writing, as they are starting to do, I think they will conclude that this is part of George’s legacy that will not earn a permanent place in history.

To summarize our progress so far, individualism according to Williams’ principle is dead and the concept of the gene as the fundamental unit of selection holds no comfort for individualism either. Only one more gasp left to go.

To be continued…


  1. #1 Markk
    January 16, 2011

    If you want to talk about the gene level of selection then aren’t ideas like species or individuals just levels of human models? Wouldn’t the entire genome in the sense of the set of all locations of a “gene” in all places across all living things be a more correct way to look at objects of selection? What matters if species survive if all the genes from that species are in other places? In this view they are the ultimate units.

    In fact at that point the definition of a gene and its fuzziness along with meta-level effects mess things up even more. I think ideas like these – individual selection, group selection, and selfish-gene type selection are nice models, but to an outsider like me, they are all wrong and all limited. They are all models that don’t exactly match reality. So the question really is which are easiest and most useful to derive results that predict and give insight to nature?