Giraffe pelvis, though relatively short, has an ilium that is outspread at the upper ends. A giraffe has only two gaits: walking and galloping. Walking is done by moving the legs on one side of the body at the same time, then doing the same on the other side. When galloping, the hind legs move around the front legs before the latter move forward, and the tail will curl up. The animal relies on the forward and backward motions of its head and neck to maintain balance and the counter momentum while galloping. The giraffe can reach a sprint speed of
Giraffe of faster evolution. The divergence of giraffe and okapi lineages dates to around 11.5 mya. A small group of regulatory genes in the giraffe appear to be responsible for the animal's stature and associated circulatory adaptations. The IUCN currently recognises only one species of giraffe with nine subspecies. In 2001, a two-species taxonomy was proposed. A 2007 study on the genetics of "Giraffa", suggested they were six species: the West African, Rothschild's, reticulated, Masai, Angolan, and South African giraffe. The study deduced from genetic differences in nuclear and mitochondrial DNA (mtDNA) that giraffes from these populations are reproductively isolated and