Controversy

What remains controversial are the exact mechanisms of selection. The most popular theory posits that protection offered by dark skin from UV irradiation becomes a liability in more polar latitudes due to vitamin D deficiency. Also, the hunter gatherer populations with dark skin, short stature and curly hair have attracted much attention. The genetic mechanism underlying the shared phenotypes among these geographically distant populations, from Central Africa, the Andaman Islands, Southeast Asia and Oceania, are still controversial, for example, whether they were the common descent from a pre-Neolithic substrate of humanity or a consequence of convergent evolution. The lifetime cumulative incidence of skin cancer approaches 50%, yet the oxymoronic "smart tanning" industry continues to grow, and there is controversy over the extent to which different types of melanin can influence susceptibility to ultraviolet (UV) radiation. The most important  is that skin tone has sometimes been used in an (often controversial see racism) attempt to define human races. On a cultural level, color terminology for race has evolved, based upon genetic variations in human skin tone and changing customs or traditions of what arbitrary criteria and the amount of categories to use.