"Peoples with light skin colours evolved over thousands of years in northern temperate climates. Human groups intermittently migrating into Europe and the northern parts of the Eurasian landmass over the past 25,000–50,000 years experienced a gradual loss of skin pigmentation. The changes were both physiological and genetic; that is, there were systemic changes in individuals and long-range genetic changes as a result of natural selection and, possibly, mutations. Those individuals with the lightest skin colours, with lowest amounts of melanin, survived and reproduced in larger numbers and thus passed on their genes for lighter skin. Over time, entire populations living in northern climates evolved lighter skin tones than those individuals living in areas with higher levels of sunlight. Between populations with light skin and those with the darkest coloration are populations with various shades of light tan to brown. "