Origins of the ‘cradle of humankind’ more diverse than previously thought

Researchers say humankind development should be viewed as mosaic-like across African continent.

OXFORD, Eng. – A team of international researchers now argue for a rewriting of early human evolution after examining distinctive physical features that impacted early development before emerging as the contemporary understanding of our modern species from tens or hundreds of thousands of years of cultural exchange.

Dr. Elanor Scerri, evolutionary archaeologist at Oxford University, lead the research team, saying isolation of our early human forebears impacted development, shedding light on a different perspective of our ancestry.

The key point we made is not just about this spread, but that these groups don’t seem to have randomly exchanged genes over time,” Scerri said in an interview with States of Life. “Instead they seem to have often spent long periods of time in isolation to each other. Instead of a tree, our (ancestral atlas) would have looked more like a dynamic wheel, with the spokes connecting different sub-populations of the overall metapopulation at different times.”

A broader view of the African continent and its impacts on development helped reconcile conflicting interpretations of early Homo sapiens fossils scattered from sites found in South Africa (Florisbad) to Ethiopia (Omo Kibosh) and (Jebel Irhoud) Morocco, Scerri noted.

The latest analysis of the team’s recent research appears to show the patchwork development of human traits could be explained by the existence of multiple populations being separated for millennia by Africa’s natural geography before blending due to climate shifts.

Scerri added these diverse environments including the “formidable” mid-latitude arid belt, a huge desert stretching from the western Sahara to the Thar Desert in India, separated various groups in turn preventing them from being “move(d) around and scatter(ed)” across the African continent, largely apart from other “more divergent” hominids such as Neanderthals in Eurasia.

“The suite of physical features that define contemporary people don’t start to appear in any single individual until sometime between 40,000 and 100,000 years ago,” Scerri said. “It seems likely that human groups were scattered and semi-isolated for much of prehistory, and the high degree of physical diversity of early humans is likely to be a reflection of this.”

This fragmentation and isolation drove genetic diversity, according to Scerri. The paper published in the journal Trends in Ecology and Evolution shows the use of more sophisticated stone tools, jewelry and cooking utensils supports the theory of just how drastically impacted early populations were by extreme isolation, rather than developing from a singular physical location and origin of our species.

The further away different groups were, the less likely they were to exchange genes and this drove a pan-African mosaic of differences that were ultimately homogenized through the spread of agriculture, many thousands of years later,” Scerri said. “The fact that genetic diversity was compartmentalized like this for so long may even have played a major role in our success.”

The group of researchers examined early fossil, genetic and climate data from a multilateral perspective with an aim to eliminate predetermined biases in the field of early human evolutionary science stemming from competing research disputes between south and east African archeological teams. 

“We certainly haven’t identified the only processes that shaped our evolution, but we think we have identified some fundamental ones when we say we need to think about population structure,” Scerri said. “This has helped us to think about what new research directions we should go in to elucidate this further.”

Through the research, Scerri said this developing framework allowed for more in-depth questions to be raised, rather than fitting early human development with previously-held research.

“I wanted to both create a better understanding across disciplines as well as pose the question: ‘Which competing theory of human origins best fits the body of data as it stands?’ Scerri said. “To do this, I didn’t go for the usual conference format with speaker presentations. Instead we focused on intense thematic discussions and in the process we were all able to bring a lot to the table.”

At present, Scerri will direct an “extensive” new fieldwork program across western Africa, one of the most poorly understood subregions of the content related to human evolution. In the west African program, Scerri and others will continue to explore existing data in different ways, trying to “find new models and methods” to better understand early human evolution.

It will certainly be interesting to see how information from this region compares with what we know from other areas of Africa,” Scerri said.

Dr. Eleanor Scerri is a postdoctoral fellow with the institute of Archaeology of the British Academy at Oxford University. As an evolutionary archaeologist concerned with understanding early human evolution from a material cultural perspective to shed light on behavioral, cognitive and cultural processes of our early ancestors. Her expertise sits within a larger field of research concerned with human origins drawing data from climate science, chronology, genetics and physical anthropology.

(Image credit Gulshan Khan/AFP/Getty Images) A replica of a Homo naledi: Various locations vie for the title of ‘cradle of mankind’ or the ‘source of humanity’, but new research is changing the perspective on early human evolution.

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