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 age of the Taung child remains more difficult to determine and is the focus of a current dating project. Australopithecus africanus Australopithecus africanus is an extinct ("fossil") species of the australopithecines, the first of an early ape-form species to be classified as hominin (in 1924). Recently it was dated as living between 3.3 and 2.1 million years ago, or in the late Pliocene and early Pleistocene times; it is debated as being a direct ancestor of modern humans. "A. africanus" was of slender, or gracile, build and has been found only in southern Africa at four sites: Taung (1924), Sterkfontein