What would it take for you to give your life to save another? The answer of course is two siblings or eight cousins, that is, if you’re thinking like a geneticist. This famous quip, attributed to the British biologist J.B.S. Haldane, is based on the premise that you share on average 50% of your genes with a brother or sister and 12.5% with a cousin. For altruism to be worth the cost it should ensure that you break even, genetically speaking.
This basic idea was later formalized by the evolutionary theorist William Hamilton as “inclusive fitness theory” that extended Darwin’s definition of fitness–the total number of offspring produced–to also include the offspring of close relatives. Hamilton’s model has been highly influential, particularly for Oxford evolutionary biologist Richard Dawkins who spent considerable time discussing its implications in his 1976 book The Selfish Gene. But in the last few years an academic turf war has developed pitting the supporters of inclusive fitness theory (better known as kin selection) against a handful of upstarts advocating what is known as group selection, the idea that evolutionary pressures act not only on individual organisms but also at the level of the social group.
The latest row was sparked by the publication of Edward O. Wilson’s new book, The Social Conquest of Earth, which followed up on his 2010 paper in the journal Nature written with theoretical biologists Martin Nowak and Corina Tarniţă. In both cases Wilson opposes kin selection theory in favor of the group selection model. For a revered scientist like Wilson–a Harvard biologist, recipient of the Crafoord Prize (the Nobel of the biosciences) and two-time Pulitzer prizewinner–to adopt a marginal and widely disputed concept has received a lot of attention and caused other prominent scientists to step forward and defend the mainstream point of view.
For example, writing at The Prospect magazine, in what The Guardian newspaper called “a searingly critical review,” Dawkins argued that the proposal in Wilson’s book was based on “erroneous and downright perverse misunderstandings of evolutionary theory.” Joining him at the website Edge was Harvard psychologist Steven Pinker who wrote that group selection was a “false allure” and “a loose metaphor, more like the struggle among kinds of tires or telephones.” Likewise, University of Chicago biologist Jerry Coyne dismissed group selection on his blog as “a fuzzy and nebulous concept” and one that merely “has an innate appeal to those with a penchant for the religious and the spiritual.” It should go without saying that online commenters were considerably less kind (a notable exception being at Edge, where scholars were invited to comment independently).
Taken together, along with the 137 scientists who signed a letter to Nature in 2010 supporting kin selection, this would seem to be the coup de grâce effectively sending group selection the way of the dodo. But, at the same time, it seems odd that so many prominent scientists would feel the need to forcefully defend what they all maintain is an irrefutable, textbook understanding of evolutionary biology. After all, science advances based on empirical evidence, not rhetoric (“An ounce of algebra is worth a ton of verbal argument,” as Haldane noted). Shouldn’t it therefore be an easy task to simply examine the evidence for group selection and leave it at that? Yes, it should in theory. But this is where things get complicated.