Reproductive isolation from a cross between a horse and a donkey or between a mare and a donkey, respectively. These animals are nearly always sterile due to the difference in the number of chromosomes between the two parent species. Both horses and donkeys belong to the genus "Equus", but "Equus caballus" has 64 chromosomes, while "Equus asinus" only has 62. A cross will produce offspring (mule or hinny) with 63 chromosomes, that will not form pairs, which means that they do not divide in a balanced manner during meiosis. In the wild, the horses and donkeys ignore each other and do not
Australopithecus africanus Little Foot is currently classified as (lumped into) "Australopithecus africanus"; Clarke suggests that Little Foot doesn't belong to either species "afarensis" or "africanus," but to a unique "Australopithecus" species found at Makapansgat and Sterkfontein (and named "Australopithecus prometheus" by Raymond Dart). Analysis made in 2015 by a new radioisotopic technique dated the Little Foot specimen to about 3.7 mya. "A. africanus" was similar in many traits to "A. afarensis", a bipedal hominin with arms slightly longer than the legs (a physical trait also found in chimpanzees). It has slightly human-like, advanced cranial features (seen in the crania of Mrs. Ples