How were human genetics shaped by early migrations from Africa

Early anatomically modern human evolved in Africa, possibly east Africa, at least 200,000 years ago. However, recent finds suggest this might be older. Population bottlenecks, or a reduction in population size, resulted in a relatively less genetically diverse population that would eventually influence all human populations today. Migration out of Africa ensured that the genetic makeup began to be less diverse as humans migrated to other regions and continents.

Population Bottleneck

Between 80,000-70,000 years ago, a population bottleneck has been proposed for modern humans. There is evidence of major climatic change at around this time, perhaps triggered by a super volcanic eruption activity in Lake Toba, Indonesia, that led to rapid global cooling. Some have suggested this led to a diminished modern human population, resulting in a more limited gene pool for modern humans. Others have suggested that the bottleneck may have been triggered much earlier, at about 100,000 years ago. In effect, what results do show is that the genetic diversity is relatively limited for many modern human populations. Where there is greater diversity is found in Africa itself, where different modern African populations show far greater genetic diversity than the rest of modern human populations in all other regions of the globe. Human in general are much less genetically diverse than many other types of animals. Overall, this lack of diversity has suggested a limited number of humans may have been responsible for the variety of populations today. The relatively greater genetic diversity in Africa suggests humans were evolving like many other species in Africa, creating new populations over time. Climatic effects or crises may have then triggered a large-scale migration out of Africa that subsequently led to the more narrow genetic diversity found today in other regions.