Why some scientists say Botswana is ancestral home of all modern humans

Archaeologists have shown evidence that land situated off the Zambezi River in Botswana is the ancestral home of modern humans. Modern humans are believed to have settled at this site for at least 70,000 years. The location was also the original home of early men in Africa some 200,000 years ago, as reported by the Guardian.

The modern human was compelled to relocate to new territories from the site as a result of unfavorable climate conditions and poor rainfall patterns. A Geneticist and senior author on the study at the Garvan Institute of Medical Research in Sydney, Prof. Vanessa Hayes, said there has been public knowledge that modern humans originated in Africa 200,000 years ago but the research community was unaware of the exact location they stayed.

The finding was categorical that the ancestral home region of all modern humans who eked out a living was present-day Botswana. The researchers arrived at this conclusion following an analysis of 1,217 samples of mitochondrial DNA, which literally is the genetic material in tiny battery-like mitochondria found in most cells.

The researchers analyzed the DNA samples from people of South African origin, including the Khoisan, a tribe whose dialect is heavy on click consonants and are traditional foragers. The researchers drew the ancestral lineage of modern humans from DNA they collected exclusively from mother to child which had been passed over generations.

The report which was published in the Nature journal said the family tree of modern humans could be connected to settlers in Namibia, Botswana and Zimbabwe. The researchers consolidated their findings by looking into the geological, archaeological and ancient remains connected to the region at the time.

Prof. Hayes said they identified a body of water the size of New Zealand called Makgadikgadi which occupied the area. She said over a period of time the water went extinct resulting in the area becoming a wetland over 200, 000 years ago.

She explained that the modern human exodus to other parts of the world began some 130,000 years ago to northeast areas where the land was fertile and had good rainfall patterns. However, the north-east settlement suffered another mass migration 20,000 years later as the rainfall pattern shifted to the south-west. Prof. Hayes indicated that those who settled in north-east eventually became farmers while those who moved south-west became foragers.

She said anyone who describes them as the first human explorers would not be far from right. Other researchers have raised concerns about linking Botswana to the ancestral home of modern humans on grounds of genetic sampling.

Researcher of human origins at the Natural History Museum in London Chris Stringer said the researchers should tarry in making references from modern genetic distributions and being definite about the location of the ancestral home.

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He said the flaw of the conclusion was the method of inference where researchers rely on one particular region, stone tool or remains to make a generalized statement. He added that the analysis of male inherited Y chromosomes will lend itself to the conclusion that Y-carrying ancestors originated from West Africa.