Presentation on theme: "“Selfishness beats altruism"— Presentation transcript:
1 “Selfishness beats altruism within groups. Altruistic groups beat selfish groups. Everything else is commentary.”or is it?
2 Darwin was a “group-selectionist”… “How the workers have been rendered sterile is a difficulty; but not much greater than that of any other striking modification of structure; for it can be shown that some insects and other articulate animals in a state of nature occasionally become sterile; and if such insects had been social, and it had been profitable to the community that a number should have been annually born capable of work, but incapable of procreation, I can see no very great difficulty in this being effected by natural selection”Page 236…or at least did not bother to discuss kinship
3 Darwin was a “group-selectionist”… “It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe an increase in the number of well-endowed men and an advancement in the standard of morality will certainly give an immense advantage to one tribe over another.”Page 236Here he recognizes the problem but still doesn’t think much of it:Within groups nice guys tend to lose out, but it provides an advantage to their groups. Two opposing forces of selection
5 Following Darwin there wasn’t much critical discussion of individual and group selection as alternativesUntil Wynne-Edwards marshaled the idea of population regulation via processes that he thought was evidence for adaptation at the group levelPrudent use of resources, territoriality etc..W-E was operating from a population perspective, whereas Lack was operating from an individual-centric view
7 The Demise of Group Selection The argument against group selection:Selective forces at the group level, if they oppose selective forces at the individual level, will tend to lose out except in very limiting circumstances (Maynard Smith)GS still theoretically possible and required to explain if the adaptations that W-E proposed really exist (Williams), but no evidence for such adaptations that require a special explanation beyond individual competition (Lack)Apparent behaviors of helping can be explained by alternative hypotheses such as kin selection, reciprocity etc…“Enormous credit would accrue to anyonewho could pull off the seemingly impossible and rehabilitate group selection. . . But actually, such rehabilitation can’t be achieved, because the great heresy really is wrong.”
8 Genic selection (selfish genes): what gets selected are genes not even individuals. Individuals are merely vehicles, lumbering robots carrying the real thing, the gene (well, technically, a whole group of them)
10 W2: The return of group selection Empirical evidence:Evolution of restraint in host-parasite systemsKerr et al. Nature, 2006
11 W2: The return of group selection Empirical evidence:Evolution of sex ratiosAviles, 1986, Am Nat
12 W2: The return of group selection Empirical evidence:Humans
13 W2: The return of group selection Empirical evidence:Eusociality (Thursday)Wilson and Hölldobler, 2005, PNAS
14 W2: The return of group selection Are alternatives really all that different?W2 Argue that they are not, kin selection, reciprocity etc do not change basic vector calculus of multi-level selection. They are simply alternative ways of defining what a “group” is…
15 Bill Hamilton: Hamilton is very skeptical of group selection and proposes inclusive fitness as an alternative 1975: Hamilton still criticizes the “recent trend in evolutionary thought” of group selection, however, extends the concept of inclusive fitness to cover group selection (George Price’s influence) 1981: “group selection results from a misreading of evolutionary theory
16 Inclusive fitness (or what?) Multi-level selection:Trait groups etc.group selection: discrete groupsof non-relativesKin selection: relativesinteracting in continuouspopulationsSober and WilsonDiscrete groups of relativesInclusive fitness:group selection: discrete groupsof non-relativesKin selection: relativesinteracting in continuouspopulationsHamilton, 1975Discrete groups of relativesNon-related individuals in continuous populations
17 “It is generally assumed that inclusive fitness is merely kin selection. However, as Hamilton pointed out, inclusive fitness theory is much more general than kin selection. Specifically, when considering the evolution of altruism, inclusive fitness theory states that what is necessary is a statistical association of (altruistic) genotypes (or partners). Kinship is only one way in which this can occur (albeit the most obvious). Alternatives include altruists recognizing fellow altruists as such and repeatedly interacting with them (e.g. through tit for- tat type strategies in prisoner’s dilemma games or green beard genes), patterns of dispersal leading to altruists settling together, and selection creating positive correlations between altruistic individuals” (p.19)Griffin and West, 2002, “Kin selection: fact and fiction” TREE, vol. 17
18 “There are three different ways of partitioning social selection: (i) the inclusive fitness extension of individual selection; (ii) the direct fitness model of individual selection; (iii) and the within and- between group selection model. Fletcher et al. spend most of their time advocating the second (a form of kin selection theory) but then conclude that group selection is best. In reality, all three models are important and useful tools for investigating and modeling social evolution and, if applied carefully, will give the same answers.” (p. 601)Foster, K. R., Wenseleers, T., et al There is nothing wrong with inclusive fitness. TREE, Vol. 21
19 Modern group selection theory is as mathematically rigorous as individual selection or inclusive fitness theory. I say this despite being someone who favors the inclusive fitness approach and whose entire career has been based on it. I think of these less as alternative theories that make different predictions than as two different languages describing the same world.…. Pinker is therefore correct that multilevel selection results can usually be seen as restating things we already knew in a different language . But I am loath to say that just because I speak English, others cannot speak in (as homage to Peter Kropotkin) Russian. Dave QuellerSo why can’t we get along?
20 Take home message questions Are W2 right about the theoretical disarray in sociobiology?How useful is group selection perspective to your research?Are there “group-level adaptations”?