Editing Albinism in humans (section)

===Evolutionary theories===
It is suggested that the early genus ''[[Homo]]'' (humans in the broader sense) started to evolve in East Africa around 3 million years ago.<ref name="royalsocietypublishing.org">{{Cite journal |last=Greaves |first=M. |date=2014 |title=Was skin cancer a selective force for black pigmentation in early hominin evolution? |journal=Proceedings of the Royal Society B: Biological Sciences |volume=281 |issue=1781 |pages=20132955 |doi=10.1098/rspb.2013.2955 |pmc=3953838 |pmid=24573849}}</ref> The dramatic [[phenotype|phenotypic]] change from the ape-like ''[[Australopithecus]]'' to early ''Homo'' is hypothesized to have involved the extreme loss of body hair – except for areas most exposed to UV radiation, such as the head – to allow for more efficient [[thermoregulation]] in the early hunter-gatherers. The skin that would have been exposed upon general body hair loss in these early proto-humans would have most likely been non-pigmented, reflecting the pale skin underlying the hair of our chimpanzee relatives. A positive advantage would have been conferred to early hominids inhabiting the African continent that were capable of producing darker skin – those who first expressed the [[eumelanin]]-producing [[MC1R]] [[allele]] – which protected them from harmful epithelium-damaging ultraviolet rays. Over time, the advantage conferred to those with darker skin may have led to the prevalence of darker skin on the continent. The positive advantage, however, would have had to be strong enough so as to produce a significantly higher reproductive fitness in those who produced more melanin. The cause of a selective pressure strong enough to cause this shift is an area of much debate. Some hypotheses include the existence of significantly lower reproductive fitness in people with less melanin due to lethal skin cancer, lethal kidney disease due to excess [[vitamin D]] formation in the skin of people with less melanin, or simply natural selection due to mate preference and sexual selection.<ref name="royalsocietypublishing.org" />

When comparing the prevalence of albinism in Africa to its prevalence in other parts of the world, such as Europe and the United States, the potential evolutionary effects of skin cancer as a selective force due to its effect on these populations may not be insignificant.<ref name="royalsocietypublishing.org" /> It would follow, then, that there would be stronger selective forces acting on albino individuals in Africa than on albinos in Europe and the US.<ref name="biomedcentral.com">{{Cite journal |last=Hong |first=E. S. |last2=Zeeb |first2=H. |last3=Repacholi |first3=M. H. |date=2006 |title=Albinism in Africa as a public health issue |journal=BMC Public Health |volume=6 |pages=212 |doi=10.1186/1471-2458-6-212 |pmc=1584235 |pmid=16916463 |doi-access=free}}</ref> In two separate studies in Nigeria, very few people with albinism appear to survive to old age. One study found that 89% of people diagnosed with albinism are between 0 and 30 years of age, while the other found that 77% of albinos were under the age of 20.<ref name="biomedcentral.com" />

However, it has also been theorized that albinism may have been able to spread in some Native American communities, because albino males were culturally revered and assumed as having divine origins. The very high incidence of albinism among the Hopi tribe has been frequently attributed to the privileged status of albino males in Hopi society, who were not required to perform physical work outdoors, shielding them from the harmful effects of UV radiation. This privileged status of albino males in Hopi society allowed them to reproduce with large numbers of non-albino women, spreading the genes that are associated with albinism.<ref>{{Cite book |last=Hedrick |first=Philip W. |url=https://books.google.com/books?id=rzoLdpRMR1gC&dq=albino+male+sexual+hopi&pg=PA186 |title=Genetics of Populations |date=2005 |publisher=Jones & Bartlett Learning |isbn=9780763747725 |pages=2, 186 |language=en |quote="An often-cited example of pleiotropic effects of viability and male-mating success in humans is for albinism in Hopi Indians, a small tribe in northern Arizona."}}</ref><ref>{{Cite book |last=Shuttleworth |first=Russell P. |url=https://books.google.com/books?id=nacDq2gTeAQC&q=albino+male+sexual+hopi |title=The Pursuit of Sexual Intimacy for Men with Cerebral Palsy |date=2000 |publisher=University of California, San Francisco |page=74 |language=en |quote="The apparent reason for this phenomenon is that albino Hopi men developed a sexual advantage over non-albino men."}}</ref>