I read a very interesting article in bbc.com today and after reading it, remembered having written a post about the antiquity of dogs and the peopling of America.
In it I questioned the authors point of view and wrote: "In my opinion what is missing in the charts is the growth and transition phases of the "S" curve. Dogs did arrive in the New World, but not 9 kya, they arrived 20 or 30 kya, or probably earlier; they probably even originated there and spread to Asia.".
I am a "dog person" and enjoy their company greatly, and most of all, that of my boxer "daughter" Kika. So when the antiquity of dogs is discussed, I have the gut feeling that dogs and humans have enjoyed quite a long and fruitful relationship, not one just 15 ky old, but something much older, in the tens of thousands of years.
The article I read today in bbc.com (DNA hints at earlier dog evolution By Pallab Ghosh) says: "A genetic study indicates that dogs may have begun to split form wolves 27,000 years ago.". It cites a paper by Skoglund, Ersmark, Palkopoulou and Dalén, which can be read in full, has some very interesting findings:
We find that calibration using the most commonly assumed mutation rate of 1 × 10−8 per generation and a 3-year gray wolf generation time would imply that the Taimyr wolf diverged from the Chinese wolf 10,000–14,000 years ago (Figure 3), which is incompatible with its calibrated direct radiocarbon date of ∼35,000 years BP. Instead, the mutation rate must be substantially slower in order to be compatible with the age of the Taimyr individual, and we find that the Taimyr divergence can be accommodated by a mutation rate of 0.4 × 10−8 per generation (Figure 3). However, it should be noted that this assumes that the Taimyr wolf is directly ancestral to the Chinese gray wolf. If there was structure between the ancestors of the Chinese wolf and the Taimyr wolf, the mutation rate would have to be even slower, and as such a rate of 0.4 × 10−8 per generation is conservative. We emphasize that this mutation rate is for non-CpG sites, since SNPs in CpG dinucleotide context were excluded from the variants called in the present-day genome. Alternatively, our results could indicate that the generation time is longer than 3 years, or some combination of slower mutation rate and a longer generation time. Regardless, this direct evidence suggests a longer timescale of wolf-dog population history and thus implies that the 11,000−16,000 years ago wolf-dog divergence inferred in a previous study [15] should be recalibrated to ∼27,000–40,000 years ago.[1]
So they question the mutation rate (the molecular clock that I have criticised so often) and suggest it should be slower. They also question generation length.
They conclude that dogs and wolves split 27 to 40 kya. That is much older than the mainstream 15 kya.
They add that: "Such an early divergence is consistent with several paleontological reports of dog-like canids up to 36,000 years old, as well as the evidence that domesticated dogs most likely accompanied early colonizers into the Americas".
And that is what I believe and surely we will find more proof of an early presence of dogs in America. By the way, the tree published as part of the paper shows American dogs closer to the root of the tree than other Old World ones...
Sources:
[1] Ancient Wolf Genome Reveals an Early Divergence of Domestic Dog Ancestors and Admixture into High-Latitude Breeds (2015), Pontus Skoglund, Erik Ersmark, Eleftheria Palkopoulou, Love Dalén, Current Biology. DOI: http://dx.doi.org/10.1016/j.cub.2015.04.019
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