how a population of wolves may have undergone speciation to form the first population of dogs
Evolution of the wolf Canis dirus[37] lived in the late Pleistocene to early Holocene in North and South America [38] and was the largest of all Canis species.[15]:52 In 1987, new hypothesis proposed that a mammal population could give rise to a larger form called a hypermorph during times when food was abundant, but when food later became scarce the hypermorph would either adapt to a smaller form or go extinct. This hypothesis might explain the large body sizes found in many Late Pleistocene mammals compared to their modern counterparts. Both extinction and speciation - a new species splitting from an older one - could occur together during periods of climatic extremes.[39][40] Gloria D. Goulet agreed with Martin and further proposed that this hypothesis might explain the sudden appearance of C. dirus in North America, and that because of the similarities in their skull shapes that C. lupus gave rise to the C. dirus hypermorph due to abundant game, a stable environment, and large competitors.[41] Nowak, Kurten and Berta disagreed with Goulet and proposed that C. dirus was not derived from C. lupus.[18][28][42] The three noted paleontologists Xiaoming Wang, R. H. Tedford and R. M. Nowak have all proposed that C. dirus had evolved from C. ambrusteri,[15]:p52[30]:181 with Nowak stating that there were specimens from Cumberland Cave, Maryland that indicated C. ambrusteri diverging into C. dirus.[17]:p243[43] The two taxa share a number of characteristics (synapomorphy), which suggests an origin of C. dirus in the late Irvingtonian in the open terrain in the midcontinent, and then later expanding eastward and displacing its ancestor C. ambrusteri.[30]:181