Similar rates of morphological evolution in domesticated and wild pigs and dogs.

Background: Whether the great morphological disparity of domesticated forms is the result of uniformly higher evolutionary rates compared to the wild populations is debated. We provide new data on changes of skull dimensions within historical time periods in wild and domesticated dogs and pigs to test if domestication might lead to an accelerated tempo of evolution in comparison to the wild conspecifics. Darwins and Haldanes were used to quantify evolutionary rates. Comparisons with evolutionary rates in other species and concerning other characteristics from the literature were conducted.

Results: Newly gathered and literature data show that most skull dimensions do not change faster in domesticated breeds than in wild populations, although it is well known that there is extensive artificial selection on skull shape in some dog breeds. Evolutionary rates among domesticated forms and traits (e.g., production traits in pigs, and racing speed in some horses and greyhounds) might vary greatly with species and breeding aim.

Conclusions: Our study shows that evolutionary rates in domestication are not in any event faster than those in the wild, although they are often perceived as such given the vast changes that appear in a relatively short period of time. This may imply that evolution under natural conditions - i.e., without human intervention - is not as slow as previously described, for example by Darwin. On the other hand, our results illustrate how diverse domestication is in tempo, mode, and processes involved.