Derived PLK4 variant not common in Bushmen

I get sad when I read things like this in Slate, Twitter at the Crossroads: The company knows it’s in trouble. And its options are bleak. That’s because in areas such as genomics so much of the cutting-edge discussion has moved to Twitter that you can be privy to information which was previously the purview of the “scientific 1%.” Today for example I see the above from Pontus Skoglund.

I’ve discussed this issue before, Miscarriage as a behavioral strategy and Human uniqueness is not unique. Basically a derived mutational variant is found in PLK4 which is correlated with higher miscarriage rates, and seems to be maintained at appreciable frequencies by balancing selection. Derived because Neandertals carry the ancestral variant. Balancing selection because 1000 Genomes results make it pretty clear that it’s not fixed or absent all across Africa, Eurasia, and the New World. If it increases miscarriage rates, why isn’t it extinct yet? If it is beneficial, why isn’t it fixed somewhere? Ergo, balancing selection presents itself as an option.

But above Skoglund reports that it does seem nearly absent among the Bushmen. Or at least among the Ju’/hoansi. What about that 1 copy among the 38? Well, the Bushmen are admixed somewhat with newcomers to the region, so it could be a recent introduction. I asked Skoglund about the Pygmies, and he reported that it is at low frequencies in the Mbuti. It may be that this variant differentiates African hunter-gatherers from the rest of humanity. Remember that the latest genomic data implies that Bushmen diverged from the main lineage leading to other human groups about ~1/3 of the time back to the divergence the ancestors of Neandertals from those of modern humans. Depending on the measure and genetic data the agriculturist Sub-Saharan Africans may actually be closer to the rest of non-African humanity than they are to extant hunter-gatherers, at least the non-admixed ones.*

Addendum: Years ago Greg Cochran told me that Pygmies are reported to have very low miscarriage rates.

* Main qualifier is that human genetic history seems to be highly reticulate, as opposed to tree-like.

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