For a long time, scientists have agreed that human life began in Africa. Just where in Africa has never been positively identified. A new study, led by Vanessa Hayes of the Garvan Institute of Medical Research in Sidney, Australia using mitochondrial DNA, claims to pinpoint the location to an area in Botswana, according to National Geographic.
Mitochondrial DNA is only passed down through the mother, and it is believed that all humans have a common ancestor — a mitochondrial Eve — that represents the closest maternal relative to modern homo sapiens. According to this study, there is a common single homeland where that mitochondrial DNA originated.
The study is controversial among scientists. Evolutionary geneticist Mark Thomas, from the University College in London claims Hayes’ work is “storytelling”, but University of Hawaii at Manoa geneticist, Rebecca Cann, has called the study “innovative” as it uses many disciplines to find information. Cann agrees that even if the study has errors, it will open new avenues of exploration to either prove or disprove the research which may lead to new discoveries.
The conclusion of this study, found at Nature, states that southern Africa, specifically the Makgadikgadi–Okavango palaeo-wetlands, commonly known as the Kalahari section of northern Botswana, is where the earliest modern human genetic relationships began, even though the oldest human bones found so far were in eastern Africa.
Two hundred thousand years ago, the now arid and salty location was covered in lush green plants in a wetland near what may have been the largest lake in Africa, and populations were steady. There were no huge growth spurts and no diseases or weather related emergencies to lower the population for seventy thousand years, but suddenly a change in human lineages indicated the beginnings of migrations due to the wetlands starting to dry up. Archeological evidence proves foraging for marine life up and down the south coast.
According to Science, the mitochondrial DNA of two hundred living tribal hunter-gatherers from South Africa who don’t usually have such tests done was collected and compared with a DNA bank of nearly one thousand other South Africans. The comparison indicated that the oldest known mitochondrial DNA lineage in living people is found in the Okavango palaeo-wetland. They also found that the particular DNA’s origins are from about two hundred thousand years ago — a number very close to previous estimates.
Another critic, an evolutionary geneticist from the University of Pennsylvania, Sarah Tishkoff, maintains that mitochondrial DNA traces only one genetic lineage passed from mothers to their children over time and these evolutionary mothers may have migrated to the Kalahari from elsewhere in Africa where the descendant line may have gone extinct. She believes that male Y chromosomes should have played a role in the tests as well, according to Science.
Hayes responds to the critics of her procedure by saying that most DNA is not stable during fetal development except for mitochondrial DNA. The male Y chromosome of the groups was no longer pure enough as men were more likely to have blended with other groups.
National Geographic reports that John Hawks, a paleoanthropologist at the University of Wisconsin-Madison agrees with the theory of a more mobile population that may not be the same people who were here hundreds of thousands of years back; he can agree with some of Hayes’ research, but he believes there is still much to be done before a solid conclusion can be made.
Most DNA researchers agree that everyone shares common ancestral mitochondrial DNA but it is such a small amount that some believe it is probably not possible to accurately pinpoint origins of where human life began. In the big scheme of things, DNA is a relatively new field of study and there are few definites. Yet this study can’t be discounted and with further research could prove to be the actual location of human origins.
With computer modeling and better carbon dating methods, new discoveries about where human life began are happening every day. Some scientists are leaning in the direction of DNA that combined together from different places in Africa that evolved into our species rather than a single origin. Others don’t believe that current science can find a single origin, if there is one, and scientists must modernize and broaden their approach. It appears that this question may be open for a while.