Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
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