eticulated giraffes than to the Kordofan

Giraffe subspecies are distinguished by their coat patterns. The reticulated and Masai giraffes represent two extremes of giraffe patch shapes. The former has neatly shaped patches, while the latter has jagged ones.[24] The width of the lines separating the patches also differ. The West African giraffe has thick lines, while the Nubian and reticulated giraffes have thin ones.[8]:321–22 The former also has a lighter pelage than other subspecies.[8]:322
A 2007 study on the genetics of six subspecies—the West African, Rothschild, reticulated, Masai, Angolan, and South African giraffe—suggests they may, in fact, be separate species. The study deduced from genetic drift in nuclear and mitochondrial DNA (mtDNA) that giraffes from these populations are reproductively isolated and rarely interbreed, though no natural obstacles block their mutual access.[14] This includes adjacent populations of Rothschild, reticulated, and Masai giraffes. The Masai giraffe may also consist of a few species separated by the Rift Valley. Reticulated and Masai giraffes have the highest mtDNA diversity, which is consistent with the fact that giraffes originated in eastern Africa. Populations further north evolved from the former, while those to the south evolved from the latter. Giraffes appear to select mates of the same coat type, which are imprinted on them as calves.[14] The implications of these findings for the conservation of giraffes were summarised by David Brown, lead author of the study, who told BBC News: "Lumping all giraffes into one species obscures the reality that some kinds of giraffe are on the brink. Some of these populations number only a few hundred individuals and need immediate protection."[25]
The West African giraffe is more closely related to the Rothchild and reticulated giraffes than to the Kordofan giraffe. Its ancestor may have migrated from eastern to northern Africa and then to its current range with the development of the Sahara desert. At its largest, Lake Chad may have acted as a barrier between West African and Kordofan giraffes during the Holocene