Donkey the environment. They may compete with livestock and native animals for resources, spread weeds and diseases, foul or damage watering holes and cause erosion. Few species of ass exist in the wild. The African wild ass, "Equus africanus", has two subspecies, the Somali wild ass, "Equus africanus somaliensis", and the Nubian wild ass, "Equus africanus africanus", the principal ancestor of the domestic donkey. Both are critically endangered. Extinct species include the European ass, "Equus hydruntinus", which became extinct during the Neolithic, and the North African wild ass, "Equus africanus atlanticus", which became extinct in Roman times. There are five subspecies
Equus lambei of the modern wild horse, including the domestic horse, "Equus caballus". Controversy still surrounds "E. lambei" and the divergence of other similar extinct horse species. Through examinations of the bones and teeth of "Equus lambei", many similarities can be seen with the modern horse "Equus caballus". There is also a strong resemblance to "E. lambei" in the metapodials of "E. caballus przewalskii" and the phalanges of "E. caballus lenensis" "." Metrical and morphological studies of horse teeth from the Bluefish Caves confirm the close similarity between "Equus lambei" with wild and domestic horses alive today. "E. lambei" is a "caballus"