Human Migration
approximately 250,000 years ago, the modern day human species emerged from the Lake Victoria region in Africa. They had dark skin, which protected them from the harsh intensity of the Saharan sun. However, some humans eventually migrated away from this region in Africa, out throughout the world. These migrations also ushered in many mutations that affected the color of their skin. This module discusses the simplified migratory routes that were taken by these peoples, and what mutations they encountered along the way.
70,000 to 30,000 Years Ago
60,000 to 70,000 years ago, a subset of the humans that were living in Africa migrated into the Northwest Arabian Peninsula and the Middle East. Within this group, there was a mutation in the KIT Ligand Gene (KITLG). The KITLG gene is responsible for assisting in melanocyte cell production, which goes on to produce eumelanin. As individuals migrated further from this region into the rest of the world, such as Asia, the Americas, and Europe, this mutation would further be embedded into others. However, this mutation did not occur in those who remained in sub-Saharan Africa.
Around the same time period, another migratory group traveled from Africa into the southern parts of the Arabian Peninsula, India, and eventually even into Australia. These individuals avoided the KITLG mutation, thus retaining dark skin.
30,000 to 40,000 years ago, those located in the northern regions of the Arabian Peninsula further migrated into Europe, West Africa, and into northern Asia.
25,000 to 15,000 Years Ago
25,000 years ago, the peoples in Europe expanded further still into the most northern reaches of the continent, at high latitudes where the winters were cold, dark and severe. More mutations occurred, this time within two transporter proteins called SLC24A5 and SLC45A2. These proteins assisted in eumelanin production, thus levels of eumelanin were reduced even further and lighter skin ensued.
Also around 25,000 years ago, a group that migrated northeast out of the Arabian peninsula and into the eastern edges of Asia experienced a mutation as well, this one occurring within a gene called MFSD12. MFSD12 plays an important role in the production of pheomelanin. This mutation allowed MFSD12 to be more effective, shifting this group’s skin color from darker shades due to eumelanin, to lighter shades due to the pheomelanin pigment.
15,000 years ago, humans migrated across the Bering Strait and into the Americas, moving quickly from North America into Central and South America.
12,000 Years Ago
12,000 years ago, those humans present in Europe and Asia experienced more mutations to the OCA2 and MC1R genes. Both of these genes are important in the production of eumelanin, and the mutations that occurred made them less effective, thus decreasing the amount of eumelanin produced and resulting in these individuals to have lighter skin.
Ultimately, around 10,000 years ago, humans had covered nearly all of the globe’s habitable regions. At this point in time, it was recognizable that those populations that were closer to the equator had higher eumelanin and thus darker skin, whereas those populations that were farther away from the equator had lower eumelanin, and thus lighter skin.