Popular theories of why our human ancestors gained and then lost dark skin over the course of evolution may be incorrect,according to a unusual paper by UC San Francisco authors, who propose that heavily pigmented skin evolved because it forms a stronger barrier against a host of environmental challenges. Because deeply pigmented skin requires more energy to produce, and they propose,our ancestors shed some of these pigments through natural choice as they moved north and needed less protection against these threats.
Source: phys.org