Irish Elk

Hypermorphosis in Irish Elk (Megaloceros)


    The 13' antler rack in Megaloceros was in the past argued to be an example of Orthogenesis, continued evolutionary increase in size of a structure past the point where it is adaptive. Thus it was argued that the species had become extinct because its body was no longer able to support the weight its antlers. Some scientists explained the extinction of dinosaurs in the same way. SJ Gould showed instead that deer antlers in general are positively allometric with respect to body size [measured here as height at the shoulder]. That is, antlers of Megaloceros have the expected size for a species of its size (left), and requires no special explanation. The same relationship holds within species, such that larger Megaloceros have proportionately larger antlers than smaller (right).


Text material © 2019 by Steven M. Carr