Monday, December 17, 2007

Sociobiology revisited: a new paper by Wilson and Wilson

An interesting review paper about multi-level selection was just made available (forthcomming) in the Quarterly Review of Biology by D S Wilson and E O Wilson. It's an interesting read. Here's the citation info and abstract:


David Sloan Wilson

Departments of Biology and Anthropology, Binghamton University Binghamton, New York 13902 USA

Edward O. Wilson

Museum of Comparative Zoology, Harvard University Cambridge, Massachusetts 02138 USA


altruism, cooperation, eusociality, group selection, human evolution, inclusive fitness theory, kin selection, major transitions, multilevel selection, pluralism, sociobiology


Current sociobiology is in theoretical disarray, with a diversity of frameworks that are poorly related to each other. Part of the problem is a reluctance to revisit the pivotal events that took place during the 1960s, including the rejection of group selection and the development of alternative theoretical frameworks to explain the evolution of cooperative and altruistic behaviors. In this article, we take a “back to basics” approach, explaining what group selection is, why its rejection was regarded as so important, and how it has been revived based on a more careful formulation and subsequent research. Multilevel selection theory (including group selection) provides an elegant theoretical foundation for sociobiology in the future, once its turbulent past is appropriately understood.

The Quarterly Review of Biology, December 2007, vol. 82, no. 4

They are careful about defining their terms. Here are some useful definitions:

"sociobiology is the study of social behavior from a biological perspective, group selection is the evolution of traits based on the differential survival and reproduction of groups..."
"From an evolutionary perspective, a behavior can be regarded as social whenever it influences
the fitness of other individuals in addition to the actor."
"Group advantageous traits do increase the fitness of groups, relative to other groups, even if they are selectively neutral or disadvantageous within groups. Total evolutionary change in a
population can be regarded as a final vector made up of two component vectors, within and between-group selection, that often point in different directions."

They make a point that words like 'sociobiology' and 'evolutionary psychology' have become "tainted" due to their negative associations and bad reputations in many fields. This is of course especially true in the social sciences. I have almost never heard an anthropologist use sociobiology in a positive or even neutral context (only very negative - 'oh that stuff - we know better than that') but the vast majority of anthropologists would think of sociology as a field arguing that genes cause every observable trait we might observe - a much more extreme view than that used by its actual practitioners (above in the definitions).
In a similar vein, anything related to 'group selection' carries the connotation of being an automatically naieve argument even in fields where Darwinian analysis is accepted. I am mostly a behavioral ecologist (studying macroecological patterns) and I have been guilty of this. In many cases, arguments about group selection involve people speaking past each other and missing the point, this is why Wilson and Wilson often use the term 'multi-level selection' instead. We can show that altruism is costly to a perfectly self-interested actor but that a group of altruists out-competes a group of selfish social defectors. If we are comparing groups (populations) and focus only on individual-level benefits we may indeed miss part of the picture, but on the other hand the individual does a lot better in the group that doesn't get killed off by the more altruistic group. So the tension between the two views is not always necessary. Wilson and Wilson look at cases like the evolution of eukaryotic cells and argue that group selection must have been present to get the once autonomous entities (prob some form of early bacteria) to cooperate so closely in a tightly knit network of symbiotic mutualisms that they became organelles in the same cell.

So group selection must be common, they argue. Consider this view: "If a trait is locally disadvantageous wherever it occurs, then the only way for it to evolve in the total population is for it to be advantageous at a larger scale." Is altruism really locally disadvantageous though?

Getting back to relationships between groups, if we want to talk about why different populations spread at the expense of others then I think population level fitness measures are necessary and quite uncontroversially logical. George Williams himself proposed measures of population level fitness in his 1966 treatise against the brand of group selection proposed by Wynn-Edwards and others. [One of these measures was population density or size which he thought was not as good as the second measure, the numerical stability of the population through time, but this has much larger data requirements. These discussions are definitely relevant for our discussions of human evolution.] Wilson and Wilson also point out that there is room for multi-level selection in Williams' view, he only underestimated how frequently it could be important.

They are very careful to separate cogent arguments of multilevel selection from those they label naive group selection. The level of selection needs to be appropriate for the analysis being conducted. My feeling is that we can't categorically reject arguments of selection at the level of genes, individuals, families, other groups, maybe even species in some restricted geological cases like the study of mass extinction, and maybe higher levels like ecological network structures. Here's a nice quote they bring to this issue:
"In biological hierarchies that include more than two levels, the general rule is “adaptation at any level requires a process of natural selection at the same level and tends to be undermined by natural selection at lower levels.” All students of evolution need to learn this rule to avoid the errors of na─▒¨ve group selectionism. Notice that, so far, we are affirming key elements of the consensus that formed in the 1960s."

Humans are used as an example in many cases in the paper.
"The importance of genetic and cultural group selection in human evolution enables our groupish nature to be explained at face value. Of course, within-group selection has only been suppressed,
not entirely eliminated. Thus multilevel selection, not group selection alone, provides a comprehensive framework for understanding human sociality."

There seems little question that understanding how selection may play out at higher levels will be necessary for explaining how anatomically modern humans came to spread and conquer the globe. But we do need to be cautious with how such arguments are invoked.

This paper is extremely well written and thought provoking. I recommend checking it out.

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