New evidence leads to an evolving understanding of human origins

July 20, 2018

Jay Stock, Professor in Department of Anthropology

Story by Rob Rombouts/Photo by Paul Mayne

In human evolution studies, it had long been accepted that modern humans evolved from a single region and population in Africa.

A recently released opinion, published in Trends in Ecology & Evolution, challenges this idea.

Eleanor Scerri, the lead author, brought together specialists from a number of fields to discuss population structure and complexity associated with the origin of modern humans.

The team behind the paper includes Jay Stock, Professor of in the Department of Anthropology. Stock specialized in human phenotypic variation, as reflected in fossil human skeletal remains.

“We know that the fossil evidence for modern human origins begins about 300,000 years ago but there are human remains of early modern humans spanning from Morocco to Ethiopia to South Africa, and all possess features that we would consider ‘modern’, but they don’t appear together in any one time or place,” said Stock. The evidence “could be produced by a variety of scenarios that involve considerable population size, geographic range and gene flow within Africa.”

“All the new evidence shows a greater complexity than previously assumed, and shows that the origins of our species were complex,” said Stock. The origin “occurred throughout Africa and the simple models that have dominated the literature for a number of years are no longer supported by the evidence.”

The new evidence came about through excavations in different regions, and points to the need for exploration in different areas. “We need to learn a lot more about humans in Africa during the time of our origins. Many parts of the continent have been unexplored,” said Stock. “Evidence shows there is complexity and variation all over Africa, but we still don’t know enough about it.”

Despite challenging the orthodoxy, Stock said the response has been really favourable. “Researchers have been talking about the complexity of the origin of our species for some time, but this paper provides a systematic reinterpretation of evidence that doesn’t fit the single model of Eastern African origin of modern humans.”

“The Trends in Ecology & Evolution paper brought people together to ask a big question about modern human origins, and big questions like that require evidence and data from many areas,” said Stock. “You need the expertise and input from people with diverse backgrounds. It’s only with the contributions of so many people that you get new perspectives like that emerging.”

Stock says the new ideas and variability in early humans show the roots of variations in different populations, and highlights how adaptive humans are to their environment.

“Africa has always been a very ecologically diverse continent. The fossil record shows how people colonized and adapted to environmental variation,” said Stock. “This adaptability is a key characteristic that makes us unique as a species.”

Stock has also recently contributed to research challenging other long held ideas about human origins and migration.

In one study, Stock was part of a group dating tylebongda human remains found in Saudi Arabia to 90,000 years ago, suggesting that people travelled further than initially thought during the first reported human migration into Eurasia.

Stock also contributed to research revealing patters of early human migration in the Americas, which suggests that early Indigenous populations split during the Ice Age, and later remixed at a later date.

Stock said these recent papers all show that “the more evidence we have, the more we see complexity in past, including how humans moved and interacted over great distances in the past.”
“As you start to dig into parts of the world that may be less explored,” said Stock, “it shows the picture is much more complicated.”