A few months ago the anthropologist Pat Shipman published a book, The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction. I’ve read Shipman before, and because of my interest in domestication it’s been on my radar, but I haven’t gotten around to purchasing it. The major reason is that as I understand it the title is somewhat misleading, in that there’s a lot less in the text on human-dog cooperation than one might think. Which is reasonable, it’s a speculative hypothesis at best.
Perhaps the biggest problem is that there’s no strong evidence that dogs were domesticated or distinct as early as ~35 thousand years ago, when modern humans replaced Neandertals in Europe. This comes up in a very highly rated comment on Amazon in fact. The best genetic work, Genome Sequencing Highlights the Dynamic Early History of Dogs, implies a date of ~15,000 years before the present, at the earliest.
But now it looks like it’s time to update our priors on this. Shipman’s speculative theory, still unlikely in opinion, is no longer extremely unlikely. The reason is ancient DNA. Ancient Wolf Genome Reveals an Early Divergence of Domestic Dog Ancestors and Admixture into High-Latitude Breeds:
The origin of domestic dogs is poorly understood…with suggested evidence of dog-like features in fossils that predate the Last Glacial Maximum…conflicting with genetic estimates of a more recent divergence between dogs and worldwide wolf populations…Here, we present a draft genome sequence from a 35,000-year-old wolf from the Taimyr Peninsula in northern Siberia. We find that this individual belonged to a population that diverged from the common ancestor of present-day wolves and dogs very close in time to the appearance of the domestic dog lineage. We use the directly dated ancient wolf genome to recalibrate the molecular timescale of wolves and dogs and find that the mutation rate is substantially slower than assumed by most previous studies, suggesting that the ancestors of dogs were separated from present-day wolves before the Last Glacial Maximum. We also find evidence of introgression from the archaic Taimyr wolf lineage into present-day dog breeds from northeast Siberia and Greenland, contributing between 1.4% and 27.3% of their ancestry. This demonstrates that the ancestry of present-day dogs is derived from multiple regional wolf populations.
As you can see from the figure to the left the Taymyr sample diverges at about the same time as the common ancestor of wolves and modern dogs. In other words, you have a polytomy. Not only that, but there has been introgression from the Taymyr lineage into particular northern dog populations.
Genetics and genomics are big deals. But at this point I have to point out that archaeologists have really been here the whole time. Archaeologists reported that the Amerindians brought dogs with them over through Berengia. Historians know that the indigenous people had dogs. Yet in 2010 geneticists published, in Nature, Genome-wide SNP and haplotype analyses reveal a rich history underlying dog domestication, who put the focus on the Middle East and the Neolithic revolution. There was basically no way this really made sense. Then you had a 2011 paper in PLOS ONE, A 33,000-Year-Old Incipient Dog from the Altai Mountains of Siberia: Evidence of the Earliest Domestication Disrupted by the Last Glacial Maximum. Even the authors themselves assumed that this was a “false dawn.” That this dog-like canid probably did not give rise to later dog lineages. But if the results above are correct, then in fact this 33,000 year old individual may actually be part of the extant proto-dog population.
Let’s let this sink in: if the results above hold, then the arrival of modern humans to northern Eurasia may have been coincident with the emergence of a distinct dog lineage. The term “man’s best friend” takes on a whole new meaning. The relationship between man and dog may be nearly as ancient as modern humans as we understand them, that is, populations capable of copious and protean symbolic cultural production which explode out in the archaeological record over the past ~40.000 years. In addition, I also believe we now need to totally reconceptualize how we view the relationship of wolves and dogs. Rather than an ancestral and derived set of populations, whose “species” status is only semantic convenience, they are actually sister clades. The results in this paper confirm other findings that the wolves of North America and Eurasia seem to share a post Last Glacial Maximum origin. Wolves as we understand them today may have emerged simultaneously with dogs, both descending from the melange of canid lineages which flourished during the Pleistocene. There’s a reason that feral dogs, such as dingos, do not “revert” to wolves. The ancestor may not have even been a wolf!
Additionally, the authors also note that the features of the dog which are hallmarks of domestication may themselves be derived within the dog lineage. That is, the separation of the ancestors of dogs and wolves predates the Last Glacial Maximum, ~20,000 years ago. But the evolution of dogs so that they exhibit particular derived traits may have occurred far later in time. In fact, I would hold that perhaps the true story is one of co-evolution between dogs and humans.
The ultimate moral of this true story to me is that many Pleistocene mega-fauna with wide ranges in Eurasia were subject to similar evolutionary dynamics. Extinction of distinct local lineages was the rule, not the exception. Recolonization from populations which dodged extinction was also inevitable. The phylogenetic tree was pruned repeatedly, but tempered somewhat in the ferocity of clipping by admixture and introgression, as branches fused together.