The tribe Bovini, or wild cattle, are medium to massive bovines that are native to Eurasia, North America, and Africa. These include the enigmatic, antelope-like saola, the African and Asiatic buffalos, and a clade that consists of bison and the wild cattle of the genus Bos. Not only are they the largest members of the subfamily Bovinae, they are the largest species of their family Bovidae. The largest species is the gaur (Bos gaurus), weighing up to . Bovins and humans have had a long and complex relationship. Five of seven species have been successfully domesticated, with one species (cattle) being the most successful member of their lineage. Domesticated shortly after the last ice age, there are at least 1.4 billion cattle in the world. Domestic bovines have been selectively bred for beef, dairy products and leather, and serve as working animals. However, many species of wild cattle are threatened by extinction due to habitat loss to make room for cattle farming as well as unregulated hunting. Some are already extinct like the aurochs, two subspecies of European bison and perhaps the kouprey. Etymology In 1821 British zoologist John Edward Gray described the family, subfamily and tribe Bovidae, Bovinae, and Bovini respectively. The word "Bovini" is the combination of the Latin prefix bos (written as bov-, which is Late Latin from bovinus) and the suffix -ini refers to their ranking as a tribe. Systematics Placement within Bovinae The wild cattle belong to the subfamily Bovinae, which also includes spiral-horned antelope of the tribe Tragelaphini and two aberrant species of Asian antelope, four-horned antelope and nilgai, which belong to the tribe Boselaphini. The relationship between the tribes varies in research concerning their phylogeny. Most molecular research supports a Bovini and Tragelaphini subclade of Bovinae. There are also some morphological support for this, most notably both groups have horn cores with a pedicle. The fossil record The earliest known wild cattle originated from Asia south of the Himalayas during the Late Miocene. This is not only supported by the fossil record but also the fact that south Asia has the highest diversity of wild cattle on planet, as well as the fact the southeast Asian saola is the basal most of the living species. At some point after the divergence of the three subtribes around 13.7 million years ago, bovins migrated into Africa from Asia where they have diversified into many species.