Welcome back! This is the third installation of my series on religion and group-level evolution. Last time, we left off with the raging debates between scientists who champion kin selection and those who swear by group selection. Group selection is the idea that cooperative behaviors – like caring for others’ offspring or loudly warning neighbors about predators – evolved by competition between groups. By contrast, kin selection, or inclusive fitness, insists that altruistic behaviors evolve strictly to benefit relatives. For example, when a mother babysits her sister’s child, she may seem generous and giving, but she’s actually being genetically selfish – peer through the illuminating lens of inclusive fitness theory, and you’ll find that she’s just caring for a little package of copies of her own genes.
Inclusive fitness models have dominated since the 1970s. However, in just the last few years, more scientists – including E.O. Wilson, the world’s most famous living biologist – have begun arguing for group selection instead. This has stirred up a fierce fight, rousing entire armies of opponents who passionately disagree with the very concept of group selection.
What’s their beef, specifically? First of all, they think it’s lousy science. In a 2012 essay at Edge.org, evolutionary psychologist Steven Pinker complained that group selection isn’t a scientific concept because groups, unlike individual animals, can’t literally replicate themselves. Evolution, Pinker argued, can only work when organisms reproduce themselves accurately – with fidelity – and different individuals contribute disproportionately to the next generation. For example, rabbits undergo evolution because they sexually reproduce themselves with high fidelity, such that each rabbit’s offspring shares many of its unique traits. Rabbits with adaptive traits leave more copies of their genes in population, so those traits tend to spread.
That’s how evolution works, Pinker sniffs. And groups aren’t rabbits. How, then, can groups compete in any evolutionarily meaningful way? Groups don’t prosper by replicating themselves, the way rabbits do. A successful rabbit is one that has lots of high-quality offspring, letting it leave behind beaucoup copies of its genes. And genes are discrete, countable things. They’re units. You can plug them into hard-nosed equations. But what’s the equivalent for groups? Groups don’t have “offspring.” Even when small splinter groups do shoot off from larger, parent groups, they almost never compete directly in a zero-sum way against other splinter groups. And they certainly don’t have any discrete, countable units of heritability, the equivalent of genes.
According to Pinker, the interactions between groups are structurally nothing like the interactions between organisms. The boundaries of groups are too diffuse, their behavior too unlike organisms for anything like selection to operate at their level. If groups competed against each other the way that rabbits do, what would be the criteria for success? More members? More territory? Neither of these things is truly analogous to genetic fitness.
Pinker’s critique is echoed by other opponents of group selection, from Richard Dawkins to Daniel Dennett. But this coterie of New Atheists/group-selection skeptics are close to being outright wrong. I say close to outright wrong because, if we accept their strict definitions of evolution – if evolution only involves discrete entities replicating themselves with high fidelity – then they’re technically correct: group-level selection probably doesn’t happen. But not everybody agrees that this is the litmus test for evolution.
(This post excerpt is part of the Sinai and Synapses Discussion Forum, a collection of perspectives on specific topics. It is part of our Spring 2015 series Are We More Than Our Genes? For the full post, please visit Patheos‘s blog Science on Religion).