Humanity’s homeland found in ancient Botswana

James Marshall
October 29, 2019

The team focused their research on the L0 lineage - modern human's earliest known population - and compared the complete DNA code (mitogenome) from different individuals - including other sub lineages across various locations in Africa - to see how closely they were related.

"I'm definitely cautious about using modern genetic distributions to infer exactly where ancestral populations were living 200,000 years ago, particularly in a continent as large and complex as Africa", Chris Stringer, who studies human origins at the Natural History Museum in London and was not involved in the study, tells The Guardian.

The breakthrough findings published today in the journal Nature today.

One major branch of this tree is known as L3, which arose around the time anatomically modern humans left Africa, and is today shared by all non-African populations, and some but not all within Africa.

The study shows that this oasis provided a ideal home to early humans for more than 70,000 years.

Today it is a dry and dusty land with scattered salt pans, and it is hard to believe that modern humans lived and thrived in wetlands here for 70,000 years before our ancestors began to explore the rest of Africa, and ultimately the world. "It's like looking at a big tree of which Europeans and Asians are tiny twigs above ," she concludes.

"Over time our DNA naturally changes, it's the clock of our history".

So the researchers on this study set out to create a more comprehensive catalog of the earliest human mitogenomes.

DNA tests showed the rare presence of the oldest maternal genetic lineage, called "L0", which is still borne by these populations.

"It has been clear for some time that anatomically modern humans appeared in Africa roughly 200,000 years ago", said Prof Vanessa Hayes, a geneticist at the Garvan Institute of Medical Research in Australia.

Geological evidence suggests the homeland region once housed Africa's largest ever lake system, known as Lake Makgadikgadi.

"Prior to modern human emergence, the lake had begun to drain due to shifts in underlying tectonic plates". This would have created a vast wetland region, ideal to sustain life. The conclusion, reached through analyses of mitochondrial DNA, historic climate estimates, geography, and other factors, helps pinpoint the long-debated geographic origins of our ancestors, but is not without its skeptics.

The authors' new evolutionary timelines suggest that the ancient wetland ecosystem provided a stable ecological environment for modern humans' first ancestors to thrive for 70 thousand years.

"We observed significant genetic divergence in the modern humans' earliest maternal sub-lineages, that indicates our ancestors migrated out of the homeland between 130,000 and 110,000 years ago", says Hayes.

The first migrants are ventured north-east, followed by a second wave of migrants who traveled south-west and a third population stayed in the homeland until today.

Hayes said this area is a "homeland not a cradle". This also allowed us to further speculate about the success of the southerly migrants being attributed to adapting their skills to the abundance of life in the oceans.

According to Axel Timmermann, from the Center for Climate Physics at the Institute of Basic Science in Busan, South Korea, these earliest migrations were driven by a very modern human obsession: climate change. "Our simulations suggest that the slow wobble of Earth's axis changes summer solar radiation in the Southern Hemisphere, leading to periodic shifts in rainfall across southern Africa", said Professor Timmermann in the same press release highlighting the research.

But if it was so ideal, why did our ancestors begin to explore other places between 130,000 and 110,000 years ago, first heading northeast and later southwest from the ancestral home? The study was reviewed and approved by the Ministry of Health and Social Services (MoHSS) in Namibia (#17-3-3), with additional local approvals from community leaders, and the University of Pretoria Human Research Ethics Committee (HREC #43/2010 and HREC #280/2017), including US Federal-wide assurance (FWA00002567 and IRB00002235 IORG0001762).

Other reports by Click Lancashire

Discuss This Article