Paleodogs and the date of domestication

Top. A fox skull used to illustrated greatest patatal breadth 

and condylobasal length. Bottom. A bivariate plot from 

Morey (2014) of GPB (Greatest Palatal Breadth) by CL 

(Condylobasal Length) for three groups of modern or 

Holocene wolves, and one series of established prehistoric

dogs, post-dating 10,000 BP, from North America and Europe.

 The contours indicate the range of plotted scores for each 

group. Superimposed on this plot are the corresponding values 

for several putative Paleolithic dogs. Using CL as a guide, one 

can see that the putative Paleolithic dogs are wolf-sized, but 

have unusually broad palatal dimensions. A comparable plot is 

provided by Boudadi-Maligne and Escarguel (2014: 86, Fig. 5),

 based on the same variables and using a larger series of wolves. 

That plot includes the earliest of the putative Paleolithic dogs

 considered here (Goyet Cave, Razboinichya Cave, Predmostí), 

and shows the same basic result.

In a forth coming article Morey (2014) examines the evidence for paleodogs, dogs that are older than the fossil record has traditionally supported.

Archaeological evidence has, for a very long time placed the origin of the domestic dog between 15,000 to 12,000 YBP. But, recent works report fossil evidence suggesting a much earlier origin, dating to Paleolithic times and perhaps exceeding 100,000 years. With such studies as a backdrop, scenarios for more ancient dates for dog origins and domestication have been made and they exceed 30,000 YPB. Morey examines this evidence and suggests such studies exhibit conceptual and methodological flaws.

When a series of cases for putative Paleolithic dogs is assessed, the author finds convincing cases for such dogs are confined to about the past 15,000 years. Morey looks at the timing of reproduction and skull and tooth morphometrics and with two exceptions, finds the putative Paleolithic dogs fall within the range of established wolves. See the figure for an explanation. Thus, the morphometrics do not support the assessment of these canids as dogs.

He also discusses the age at first reproduction of wolves and dogs, noting it may have been almost two years for wild wolves; and noting captive wolves may breed much sooner. The point being that even first reproduction at two years old, the generational time translates into dozens of generations over a mere few hundred years. Combined with directional selection, the wolf/dog would change its morphology substantially in a very short time. So genetic isolation was likely not in place at first, resulting in some delay in the recognizable appearance of certain domestication traits. But, genetic isolation was never complete, since dogs and wolves continue to hybridize to a limited degree to the present day. Therefore, he concludes that allowing for modest delay in the appearance of domestication changes, 16,000-17,000 YBP is a reasonable estimate for the beginnings of sustained canid domestication.

The morphometric evidence is somewhat at odds with the genetic data. One study done in 1997 suggests dogs diverged from wolves somewhere between 100,000 to 30,000 YPB. A more recent (2013) study using mitochondrial genomes estimates 33,000 to 18,000 YBP, and a yet more recent study (2014) places the divergence date of wolves and dogs between 50,000 and 11,000, although the authors, suggest that a more recent date is probable.

Resolving the differences in the molecular studies with the morphometrics promises to be challenging and as several recent authors have suggested, the domestication of the dog is much more complex than previously imagined.

Citation

Morey, D. F. (2014). In Search of Paleolithic Dogs: A Quest with Mixed Results. Journal of Archaeological Science. 52:300-307.