<P> Hairless skin, however, is particularly vulnerable to be damaged by ultraviolet light and this proved to be a problem for humans living in areas of intense UV radiation, and the evolutionary result was the development of dark - coloured skin as a protection . Scientists have long assumed that humans evolved melanin in order to absorb or scatter harmful sun radiation . Some researchers assumed that melanin protects against skin cancer . While high UV radiation can cause skin cancer, the development of cancer usually occurs after child bearing age . As natural selection favours individuals with traits of reproductive success, skin cancer had little effect on the evolution of dark skin . Previous hypotheses suggested that sunburned nipples impeded breastfeeding, but a slight tan is enough to protect mothers against this issue . </P> <P> A 1978 study examined the effect of sunlight on folate--a vitamin B complex--levels . The study found that even short periods of intense sunlight are able to halve folate levels if someone has light skin . Low folate levels are correlated with neural tube defects, such as anencephaly and spina bifida . UV rays can strip away folate, which is important to the development of healthy foetuses . In these abnormalities children are born with incomplete brain or spinal cord . Nina Jablonski, a professor of anthropology and expert on evolution of human skin coloration, found several cases in which mother's visits to tanning studios were connected to neural tube defects in early pregnancy . She also found that folate was crucial to sperm development; some male contraception drugs are based on folate inhibition . It has been found that folate may have been the driving force behind the evolution of dark skin . </P> <P> As humans dispersed from equatorial Africa to low UVR areas and higher altitudes sometime between 120,000 and 65,000 years ago, dark skin posed as a disadvantage . Populations with light skin pigmentation evolved in climates of little sunlight . Light skin pigmentation protects against vitamin D deficiency . It is known that dark - skinned people who have moved to climates of limited sunlight can develop vitamin D related conditions such as rickets, and different forms of cancer . </P> <P> The main other hypotheses that have been put forward through history to explain the evolution of dark skin coloration relate to increased mortality due skin cancers, enhanced fitness as a result of protection against sunburns, and increasing benefits due to antibacterial properties of eumelanin . </P>

A person with dark skin has a greater production of melanin than someone with fair skin