Genetic studies with mtDNA trace human ancestry 200k years ago

Genetic studies have linked the evolution of modern humans to the Kalahari region of northern Botswana. The studies employed the mitochondrial DNA (mtDNA) in its research as it is the only genetic material that doesn’t get rearranged in early fetal development like other types of DNA.

Africa stands as the origin of modern humans, about 250,000 to 300,000 years ago, as revealed by genetic studies on fossils and DNA. Genetic experts still express doubts about the authenticity of the discovery because mtDNA is not substantial enough to deliver a comprehensive history of humans.

Due to the traveling and mix of genetic material among the human population, studies based on the DNA of living individuals give a minimal scope. Ancient DNA or a well-dated fossil is preferred for genetic studies of this magnitude, said population geneticist Pontus Skoglund of the Francis Crick Institute in London.

Modern human origin from new genetic studies

Previous research studies on fossils and DNA revealed that modern humans evolved from Africa over 250,000 to 300,000 years ago, but the precise region in Africa has remained obscure.

Not until new genetic studies analyzed the mtDNA inherited only from mothers. The studies collected blood samples from foragers and hunter-gatherers in Namibia and South Africa. The DNA of these groups of individuals is poorly classified, and they speak Khoisan with click consonants.

The researchers compared the mtDNA collected from the samples and compared it with the over 1000 mtDNA in the database of South African origin. The relation of the sample to each other was represented on a family tree.

The genetic studies revealed that the Khoisan speakers have a common mtDNA with the oldest known mtDNA lineage in living people – L0. Also, the studies showed the origin of L0 to be about 200,000 years ago, with an error range of 165,000 to 240,000. Previous studies accommodated an error range of 150,000 to 250,000.

Research findings by genomicist

The genetic studies lead author, Vanessa Hayes, a genomicist at the Garvan Institute of Medical Research and the University of Sydney in Australia, said that L0 lineage is presently found in people living in South Africa. The lead author further noted that this group of persons in South Africa with the L0 lineage is the ancestral population of all living humans.

Meanwhile, population geneticist Aylwyn Scally of the University of Cambridge in the United Kingdom agreed with the findings of the studies involving mtDNA. Southern Africa plays a significant role in the evolution of humans, said, Aylwyn Scally. However, the precise location in South Africa can’t be discovered by merely studying the DNAs of living people, the geneticist added. 

Following the genetic studies findings, Hayes and her colleagues hold the view that the precise location of human evolution is the Kalahari region of northern Botswana. Currently, the Kalahari region is a desert with salt flats. Some 200,000 to 130,000 years ago, it was a lush wetland, which could have become the largest lake in Africa as postulated by climate data and simulations studies.

The research team claims the ancestral population in Kalahari homeland bearing the L0 mtDNA lived in the region for about 130,000 to 110,000 years ago. However, new mtDNA lineages discovered by the team happened as individuals moved to other areas in the northeast and southwest following climate changes.

The Y chromosomes could have been a tracking tool if it hadn’t disappeared as men mixed with other groups, said Hayes. Geneticist Sarah Tishkoff of the University of Pennsylvania noted that mtDNA is a poor tracking tool since it only identifies mother origin and not the father or both parents. Tracing the Y chromosome from fathers or any nuclear genes inherited from both parents will give better and different answers, said Sarah.

Human evolution traced to female ancestors

According to the team lead, mtDNA is the only reliable tracing tool as it doesn’t intermix in early fetal development like other types of DNA do. Thus, it is the only qualified genetic material to be used to trace human evolution to female ancestors who lived in Southern Africa.

Genetic studies critics present varying opinions about the findings. The critics warn that the female ancestors of the Khoisan speakers may not have lived in the same place 200,000 years ago. 

The critics mentioned that the ancestral women could have migrated to southern Africa from elsewhere or other parts of the world that are already in extinction.

Due to the traveling and mix of genetic material among the human population, studies based on the DNA of living individuals give a minimal scope. Ancient DNA or a well-dated fossil is preferred for genetic studies of this magnitude, said population geneticist Pontus Skoglund of the Francis Crick Institute in London.