DNA studies have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago, to as much as 100,000 to 140,000 years ago. These results depend on a number of assumptions. Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date. Some estimates of divergence dates from DNA evidence use an estimated wolf–coyote divergence date of roughly 700,000 years ago as a calibration. If this estimate is incorrect, and the actual wolf–coyote divergence is closer to one or two million years ago, or more, then the DNA evidence that supports specific dog–wolf divergence dates would be interpreted very differently.
Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding. This could significantly bias DNA analyses to support an earlier divergence date. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines
