Our African roots have many branches and interactions.
An international team led by scientists from Harvard Medical School (USA) and with Spanish participation (Institute of Evolutionary Biology and Pompeu Fabra University), has produced the first ancient human DNA sequences from the entire African genome Western and Central and confirms that the origin of modern humans came from four different African populations that lived separately between 300,000 and 200,000 years ago.
This finding reinforces the new argument made by archaeologists and geneticists that human origins in Africa may have involved widely divergent and geographically separate populations.
The remote origins of mankind
DNA analysis of west-central African children, whose remains come from a rocky place called Shum Laka, in a grassland area of Cameroon, indicate that at least three main human lineages, ancestors of African hunter-gatherers Central modern day, hunter-gatherers of southern Africa, or humans today, genetically diverged from each other about 200,000 years ago.
” Our analysis shows the existence of at least four great deep human lineages that contributed to today’s populations, and that diverged from each other between 250,000 and 200,000 years ago, ” says David Reich of Harvard Medical School and leader of the work.
Phantom lineage
A fourth human population, previously unknown, also emerged in that period of time and left a small genetic mark in modern West and East Africans, according to the study reported in the journal Nature. This ancestral lineage possessed a small amount of DNA from hominid populations that had originated before the emergence of the human species, indicating that they were possibly Neanderthals. At the moment, it indicates the existence of an archaic human lineage that we have not yet identified.
It is a “phantom lineage” – a group for which we have no physical evidence – that does not appear to have persisted to the present as a distinct population.
The researchers tried to obtain DNA from 18 different skeletons but only succeeded with four: a young child and a teenager from a single 8,000-year-old grave, and the neighboring graves of two children from roughly 3,000 years ago. The latest date is roughly similar to the beginning of the Bantu expansion, suggesting that these skeletons could reveal many details about their origin.
The mitochondrial genome, which is inherited from an individual’s mother, was not particularly illuminating, as it matches variants widely found in Africa. It was for one of the Y chromosomes, a rare version that is only found in a few modern populations in Africa and appears to have been introduced into modern humans by interbreeding with an archaic human.
This rare haplogroup (A00) was discovered seven years ago when an African-American descendant of slaves, went to a genetic analysis company and obtained results that surprised everyone.
A species on the move
A previous genetic study, led by evolutionary geneticist Pontus Skoglund of the Francis Crick Institute in London, identified a human population that originated more than 200,000 years ago and was ancestral to the hunter-gatherer groups of the sub-Saharan African rainforest. western and central. The new study provides more evidence of that ancestral line, showing that the history of humanity would not be marked by inaction and isolation, but by movement and mixing.
While this represents an interesting advance in our understanding of human history, we still have a long way to go before we have a diverse sample of genomes from African populations. Will there be more surprises? Possibly.
Referencia: Ancient West African foragers in the context of African population history, Nature (2020). DOI: 10.1038/s41586-020-1929-1 , https://www.nature.com/articles/s41586-020-1929-1
