People routinely mistake the action of adaptive evolutionary process as occurring on the level of the species. Not only is this a misunderstanding that crops up in the general public, but I’ve talked to biologists who make the same mistake. The reality is that the mainstream tradition in modern evolutionary biology is very skeptical of “for the good of the species” arguments. For me one simple reason is that I don’t think species are necessarily a clear and distinct taxonomic class. But the major factor is the reality that altruism of this sort is vulnerable to being superseded by an invading selfish free-riding strategy. As a matter of pervasive phenomena much of the “struggle for survival” that an organism experiences won’t be due to exigencies of environment or the threat from other lineages, but rather within one’s own species. Though this can be conceptualized in terms of violence, more often one can chalk it up to competition for finite resources in a Malthusian world at carrying capacity.

The logical conclusion leads to the sort of individual-level focus that is at the heart of The Selfish Gene, though Richard Dawkins’ book is to a large extent an exposition of a Neo-Darwinian tradition which goes back to R. A. Fisher, and matured with W. D. Hamilton and George Williams. But over the past few decades there has been a small group of biologists who have rebelled from the focus on individuals and genes, and made the case for selection operating at multiple levels or biological organization, from the intra-genomic all the way to “super-organisms” such as ant colonies. Rather than old-style species/group selection, the new theorists refer to “multi-level selection.” The primary force behind this movement has been David Sloan Wilson. I like David personally and he’s a great scientist (I did a BloggingHeads with him 6 years ago). But he has a tendency in my opinion of declaring unilateral victory when most people would argue that there’s still a lot to hash out, and the war continues. His new book, Does Altruism Exist?, is in my Kindle “to-read” stack, but from what I’ve seen of the reviews he does do this again! (no worries, the rest of the book looks interesting anyway)

My own views have evolved…over the years I have realized I am not entirely satisfied with models of human cultural variation that are individual level or entirely non-adaptive. I have long been broadly sympathetic to the project of Peter Richerson and Richard Boyd of using the frameworks developed in evolutionary biology to understand cultural processes. Additionally, I’m a big fan of Joe Henrich’s research, to the point of pre-ordering his book The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter six months ahead of time. There are good reasons why above-the-individual level selection would be able to operate in humans. The reduction in a verbal sense is that human cultural phenomena are such that between group variation can dwarf within group variation. The canonical example of this is language, where differences between groups are very large, and rather smaller within groups. This is simply a function of how culture, and language in particular, spreads in a population: it can be asymmetric in terms of vertical transmission. This is in contrast to genes, where you have equal contributions from both parents. One can imagine a population expanding into another where it absorbs individuals from hostile groups, changes its own genetic makeup, but by and large maintains its cultural integrity. To give a concrete example, the Xhosa people of South Africa are approximately ~25 percent Khoisan in genetic ancestry. But their culture is not “25% Khoisan.” There are influences, such as click sounds in their language, but those are accents on the basic Bantu cultural substrate which is preserved, and ties them with populations in Central and Eastern Africa.

It is a rather different matter with biological processes because of the enforced symmetry in transmission. Maintaining between group variance requires ingenious processes, which some find implausible. But ultimately it’s an empirical matter on a species-by-species basis. I would commend readers to look through first half of Wilson’s Unto Others to get a sense of how inter-demic selection processes might be ubiquitous. My position on the role that biological above-the-level-of-individual selection plays in evolution is to be skeptical in the generality but open-minded in the specifics. After all, bdelloid rotifers show that there are cases where complex asexual species can persist, even if the general rule about asexual lineages is that they are prone to extinction.

For whatever reason arguments about multi-level selection get rather heated among evolutionary biologists. It’s often closely related to the debate about kin selection (see this post from Jerry Coyne, and follow the links). I suppose David Sloan Wilson would suggest that it’s an illustration of inter-group competition, as individuals conform to particular positions due to their identity as members of a coalition.

With the preliminaries out of the way, I’d like to recommend a series of papers in the Journal of Evolutionary Biology which are open access to readers if they want to dig further (especially for those with a formal bent). First, The genetical theory of multilevel selection. The title should give some readers a clue as to the tradition which this theorists works in! Charles Goodnight makes a spirited response in Multilevel selection theory and evidence: a critique of Gardner, 2015 (his point about some researchers who come out of quantitative genetics has always been obvious to me when I read their papers; it’s a different tradition). Finally, the original author responds: More on the genetical theory of multilevel selection.

I’m not an evolutionary theorist, so I’m not going to take sides (though to be honest I always find Goodnight to be a little too vociferous for my taste, but perhaps that’s just how it comes across in print). Rather, I’m chewing through some of the ideas, and find that these papers are excellent starting points to explore the literature. It’s also nice that they’re open access, as there are people who are not in academia who might have some things to say about these topics, or, who might pursue research as a career after stumbling upon these sorts of papers.

Note: If the copious references to the Price Equation confuse, try this paper.