Steven Pinker’s essay on group selection (my initial post on it here) has now attracted a raft of interesting responses that are well worth reading. While it is hard to stitch together and reconcile the various arguments, in sum they confirm one part of Pinker’s argument. In his essay, Pinker wrote:
The first big problem with group selection is that the term itself sows so much confusion. People invoke it to refer to many distinct phenomena, so casual users may literally not know what they are talking about. I have seen "group selection" used as a loose synonym for the evolution of organisms that live in groups, and for any competition among groups, such as human warfare. Sometimes the term is needlessly used to refer to an individual trait that happens to be shared by the members of a group; as the evolutionary biologist George Williams noted,"a fleet herd of deer" is really just a herd of fleet deer. And sometimes the term is used as a way of redescribing the conventional gene-level theory of natural selection in different words: subsets of genetically related or reciprocally cooperating individuals are dubbed "groups," and changes in the frequencies of their genes over time is dubbed "group selection."
In the responses, Herb Gintis talks of gene-culture evolution. Jonathan Haidt suggests that to see group selected traits, we should look at groupishness in inter-group competition. Peter Richerson talks of cultural group selection and traits such as language. David Sloan Wilson and David Queller look at the technical alignment between inclusive fitness and multi-level selection, which is a biologically focused approach. Across the responses, most of Pinker’s varieties of group selection are covered, and many responses cannot be reconciled with the others as they are talking about different ideas.
To resolve this confusion, there needs to be greater differentiation of the various phenomena that people are trying to describe. A starting point would be removing the label of “group selection” from some of them. Daniel Dennett picks up on this point:
Pete Richerson's comment articulates the details well, but muddies the water by speaking of cultural _group_ selection. There are reasons for calling these phenomena a variety of group selection, reasons ably recounted by Boyd and Richerson in many publications, but better reasons—in my opinion—for avoiding the label, precisely because it _seems_ to give support to the vague and misguided ideas of group selection that Pinker exposes so effectively. These phenomena consist in the evolution by natural selection (both cultural and genetic) of what might be called groupishness adaptations, dispositions (or traditions) of cooperation and the punishment of defectors, and the like, but not by a process of differential _reproduction of groups_. What differentially reproduce in these phenomena are groupishness memes, not groups. The establishment of these memes may then enable the genetic evolution of enhancements in hosts—like the lactose toleration that evolved in response to the culturally spread tradition of dairying. This is no more group selection than the differential reproduction of the flora in our guts is group selection.
Personally, I would accept some of these phenomena being called group selection if they always had the prefix of “cultural” attached. At that point, some biologists will drop their instinctive opposition and the debates will be able to focus on the question of whether cultural group selection was important in the evolution of the trait of interest or is a useful framework for analysing it. As I argued in my initial response to Pinker’s piece, cultural group selection avoids some of the issues associated with “biological” group selection. Peter Richerson also makes this point:
Natural selection on large scale patterns of cultural variation is plausible because the cultural variation between neighboring groups that might compete is typically much larger than the genetic variation between the same groups. The reasons are not hard to see; all human groups are more or less open to immigration. Groups intermarry and intermarriage is a very effective conduit for genes. This is less true of culture. Because culture evolves more rapidly than genes, groups will continue to differ despite migration. A large body of social psychology research has characterized the active mechanisms that damp down variation within groups and protect between group variation from the effects of migration. Human social groups are psychologically very salient entities as Pinker acknowledges.