According to a report in October 2019, a large ancient wetlands region across northern Botswana, which is now a desert region with salt flats, may represent the ancestral homeland of all humans. The study, based on maternal DNA data from more than 1,200 people indigenous to the region of southern Africa, has suggested a crucial role for this region in the context of the early history of humans. The area, which is now dominated by desert, is seen as abounding in wetlands in the past. It provides the first quantitative evidence that climate changes in the past linked to the Earth’s axis and orbit caused major human migration events, which have been linked to genetic diversity and cultural, ethnic and linguistic identity.
The study says that our ancient ancestors first appeared just south of the Zambezi River that was once home to a huge lake, called Lake Makgadikgadi, comparable to England in size. The lake stretched all the way from Namibia, across Botswana and into Zimbabwe. Makgadikgadi began to break up about 200,000 years ago, a vast wetland was created providing a lush home abundant with plants and trees for our earliest relatives, according to a co-author of the study Axel Timmermann, a climate physicist at Pusan National University in South Korea. It was perhaps a massive extension of today’s Okavango Delta wetland area. This is the first time that a study has pinpointed the exact location where the first humans were.
The study states that beginning some 200,000 years ago, humans were nurtured here for 70,000 years before climate changes paved the way for the first migrations to other parts of the world. The place in focus is a lake that, at the time, was Africa’s largest—twice the area of Lake Victoria—which gave rise to the ancient wetlands covering the Greater Zambezi River Basin that includes northern Botswana, Namibia to the west and Zimbabwe to the east.
The study team collected blood samples from people in Namibia and South Africa and examined their mitochondrial DNA (mtDNA). As mtDNA x chromosome is passed almost exclusively from mother to child through the egg cell, its sequence stays the same over generations, and so it can be a vital means of studying maternal ancestry. The focus in this study was on the L0 lineage, referred to as the earliest known human population. The Garvan Institute of Medical Research in Sydney and University of Sydney have been involved in the study which was published in the journal Nature.
Climate computer models were used to simulate the climatic history of South Africa over the past. Climate, rainfall and vegetation shifts may have occurred due to changes in the Earth’s axis and orbit and these could have resulted early migrations of this ancestral group of people away from the homeland region. It is suggested that the slow wobble of Earth’s axis changes summer solar radiation in the Southern Hemisphere, which led to periodic shifts in rainfall across the region of southern Africa. The climatic changes would have opened green corridors full of vegetation, allowing migrations to first the northeast and then the northwest. So the climatic theory presented here is said to back the genetic evidence.
However, not everyone agrees with this story of history. The simple reason being, the more farther back the human mitogenomic tree is traced, the more uncertainty creeps into it. Interestingly, the prominent view of experts previously had been that early humans were found all over Africa and they did not emerge in any specific place. This view was suggested by a study just 2 years ago.
Importantly, fossil finds hint at the first presence of humans in East Africa, though now genetic analysis suggests that they began in South Africa. It has been long established that the first people emerged somewhere in Africa before spreading worldwide later. But what is not known is, where exactly this homeland was. Scientists say that the oldest-known Homo sapiens fossil evidence dates back to more than 300,000 years and it was found in Morocco. The new study, however, suggests that early humans as represented by the Morocco remains may not have left their lineage living today. It points out that there is no contradiction between the presence of an early Homo sapiens-like skull in Morocco, northern Africa, whose lineage may have died out, and the proposed southern African origin of the lineages that are found today. However, the Morocco fossil evidence—the oldest-known Homo sapiens fossil evidence—is dated to over 300,000 years; so how can it be said that beginning some 200,000 years ago, our ancient ancestors first appeared just south of the Zambezi River that was once home to a huge lake, called Lake Makgadikgadi, in the region of Botswana?