Razib Khan One-stop-shopping for all of my content

July 22, 2018

Wolves out of Beringia!

Filed under: Canids,Canine Evolution,Dog Evolution,Wolves — Razib Khan @ 9:05 pm
Citation: Modern wolves trace their origin to a late Pleistocene expansion from Beringia

Do Eurasian and North American wolves come from Beringia? That’s the conclusion of a new preprint, Modern wolves trace their origin to a late Pleistocene expansion from Beringia. The figure above is the main result, using ancient and modern mitochondrial genomes to construct a phylogeny. It’s not surprising that the ancient lineages are basal. Y and mtDNA lineages have a tendency to go extinct (lower effective population, etc.). But it’s a surprising result that the older Beringian individuals are distributed basal to the modern lineages, as opposed to more of the ancient samples from Europe and the Middle East.

The basic argument here is very similar to “mitochondrial Eve.” If Beringian lineages tend to be basal to modern wolves, then the former is likely to be ancestral to the latter. Additionally, as noted in the preprint there is whole-genome inference which indicates that modern gray wolves across the Palearctic ecozone underwent a rather recent demographic expansion, in particular, after the Last Glacial Maximum (~20,000 years BP). That being said, I am curious if modern Alaskan and (east) Siberian wolves exhibit greater mtDNA diversity than elsewhere, in keeping with the human analogy.

Needless to say, mtDNA has limitations. It’s a single locus, and in other animal research, there have been confusions and misunderstandings due to the usage of mtDNA. The authors did some explicit formal demographic modeling using their data. It’s fine, but generally, I ignore this stuff because it rarely tells us things we don’t know to a high degree of certainty.  Rather, I would rather focus on paleoclimate data and a model where coexistence with Beringian humans might explain a possible break-out of Beringian wolves to the west and the east after the Pleistocene. The Beringian landscape may have been particularly fertile territory for the Palearctic wolf. Though modern wolves seem to prefer some forest, rather than open territory.

One thing human evolutionary genomics has taught us is that the first-pass story is always far simpler than reality. I think this is a decent framework to start with, though it may still turn out to be wrong. But in the preprint, the authors note some peculiarities in South Asians and Tibetan wolves. So peculiar that they were discarded from the analysis. We know wolves hybridize with both jackals and coyotes, so the emergence of the modern lineages are likely more complex than a simple expansion and replacement. The whole-genome analysis will probably offer up curious wrinkles.

Though the preprint tries to put the emergence of the wolf from Beringia in the context of the domestication of the dog, I suspect we’ll find that the dog derives from an extinct Eurasian wolf lineage. This was the implication of Freedman et al., and ancient canine genomics is producing some erratic finds which are in keeping with a possible complex divergence of the dog lineage from wolves.

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