The Pinker essay has generated a lot of commentary on different websites. This can only be a good thing, insofar as channels for reactions remain open. The Social Evolution Forum is committed to this.
Needless to say, there is a tinge of hegemony in various essays on the Edge website. How can two individuals, who are diametrically opposed in their views, both be correct? One way, obviously, is if there are semantic issues permeating one or both commentaries, and that once these are ironed-out, one or both perspectives will be found to have elements of truth and/or falsehoods. We are likely never to know the outcome on semantic issues, since decades of discussion have not resolved these. What is the next step beyond these disagreements?
Anecdotal evidence, developed narratives, and comparative analyses are very good starts to organizing ideas and predictions about individual and group effects (be they traits or scales of selection). We are however generally lacking rigorous scientific approaches, and I am not very optimistic that we will go very far on human populations. However, group selection, group traits, inclusive fitness, etc. can be measured and manipulated in microbes, and in particular, in bacteria. Examples of possible traits include quorum sensing, siderophore production, and biofilm structures. I include a few references at the end of this commentary.
Briefly, we need to measure the following:
1. The traits elicited specifically when individuals interact with their(non-social) environment.
2. The traits elicited specifically when individuals are in small-scale social situations (e.g., dyads).
3. Traits elicited when individuals are in larger groups.
4. Traits that cross one or more of the boundaries in points 1-3.
An example of an experimental evolution study on microbes that investigates levels of selection is Kummerli and colleagues (2009). We need to identify and catalog these traits, explain their origins and understand their current contexts and effects. Are they adaptive, maladaptive, or neutral? When does the scale concern the individual, sub-ensembles of groups or whole groups?
This simple plan of action could be done to some extent for humans, but as I mention above, bacteria are our best bet for scientific approaches (proper controls, determination of cause and effect, possibility of phylogenetic approaches, etc.).
More than one level of selection may be acting simultaneously in any given system. The big challenge is to measure what very may well be very subtle effects and to apportion them to the level(s) of selection that they affect. Surely, some systems will be dominated by individual selection and traits; others will have an integration of individual and large-scale effects. It is frankly hard to see that group effects will not play a significant role in explaining for example, multicellularity, transitions in individuality and eusocial insect societies. Once we have data on a range of situations to describe, substantiate and refute, we can revisit the question of individual and/or group selection.
Brockhurst M.A. et al. 2006. Character displacement promotes cooperation in bacterial biofilms. Current Biology 16:2030-2034
Buckling A. et al. 2007. Siderophore-mediated cooperation and virulence in Pseudomonas aeruginosa.FEMS MicrobiolEcol 62: 135-141
Hochberg M.E. et al. 2008.The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity.BMC Evolutionary Biology 8:238
Kümmerli, R. et al. 2009.Limited dispersal, budding dispersal, and cooperation: an experimental study. Evolution63: 939-949
Nadell C.D. et al. 2009.The sociobiology of biofilms.FEMS Microbio Rev 33: 206-224.
Rainey P.B. & Kerr B. 2010.Cheats as first propagules: A new hypothesis for the evolution of individuality during the transition from single cells to multicellularity. Bioessays 32:872-880
Ratcliff W.C. et al. 2012.Experimental evolution of multicellularity.PNAS 109: 1595-1600
Velicer G.J. 2003. Social strife in the microbial world.Trends in Microbio 11:330-337