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When did social learning evolve?

Two papers this week may shed some light on human evolution. We aren't descended from modern monkeys or lemurs, but we can often learn something about our ancestors by studying our distant cousins.

colugo.jpg

If several cousins share an allele (version of a gene) that is rare in the general population, they probably inherited it from one of their shared grandparents. It's not absolutely impossible that the allele arose by independent mutations in their parents, instead, but it's much less likely. So, one of the reasons we study the genes and behaviors of related species is to figure out how far back in the human family tree a particular trait evolved. Of course, it helps to know how closely related various species are, that is, how recently a pair of species shared a common ancestor.

Molecular and Genomic Data Identify the Closest Living Relative of Primates was published in Science by Jan Janecka and others. They concluded that the closest living relative of the primates, a group which includes lemurs and monkeys as well as humans and other apes, is the colugo, the so-called "flying (actually, gliding) lemur." (I've heard of flying nuns, but primates?) They estimate that our last common ancestor lived in the Cretaceous, prior to the meteor impact that killed the dinosaurs 65 million years ago. Most primates can't glide, so this trait presumably evolved in the line that led to colugos from their common ancestor with primates.

Social diffusion of novel foraging methods in brown capuchin monkeys (Cebus apella) by Marietta Dindo, Bernard Thierry, and Andrew Whiten, was published in Proceedings of the Royal Society. They showed that, under experimentally-controlled conditions, a capuchin monkey that had been taught a particular technique for getting food could be imitated by another monkey, who was imitated by another monkey, and so on. Those taught an alternative method transmitted that method. This is the same species used in a study of symbolic token use I discussed earlier.

I will let others comment on whether the experimental setup was realistic, in terms of extrapolation from these experiments to social learning in the wild. If so, then it seems possible that the common ancestor of humans and capuchins could learn by imitating others. We would need to look at other related species before drawing that conclusion, however; octopuses can learn by imitating other octopuses, yet I doubt that our distant common ancestor could do so.

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