© Pamela Willoughby, University of Alberta
This 2012 image shows a structure used by inhabitants of the region for well over 200,000 years.
Research and excavations by a Canadian researcher from sites in southern Tanzania could lead to a rethinking of the 'Out of Africa' narrative that describes the human diaspora around the globe, according to a new report in the journal Quaternary International.

Led by Pamela Willoughby, the Iringa Region Archaeological Project has uncovered artifacts that suggest a constant human occupation between today and at least 200,000 years ago at two sites, Mlambalasi and nearby Magubike.

"Some of these sites have signs that people were using them starting around 300,000 years ago. In fact, they're still being used today," said Willoughby, from the University of Alberta's Department of Anthropology. "But the idea that you have such ancient human occupation preserved in some of these places is pretty remarkable."

The finding also supports the so-called "bottleneck theory", which says that all humans are descended from one genetic lineage of people who left Africa around 50,000 years ago.

Within the Magubike site is a large rock shelter with an intact overhanging roof. Excavations of the shelter yielded unique artifacts and fossils that date from the Stone Age to the Iron Age. Earlier artifacts from the shelter include human teeth, animal bones, shells and thousands of stone tools.

While the more recent objects can be dated with radiocarbon techniques, the older finds must go through processes such as electron spin resonance, which dates an item based on its long-term exposure to radiation. Information gathered from these techniques could be used to track the evolution of the shelter's former residents.

Over at Mlambalasi, about 12 miles from Magubike, the excavation team uncovered a fragmented human skeleton dated to about the late Pleistocene Ice Age - after the majority of the diaspora had occurred.

Previous research and other archeological finds in the Iringa region of Tanzania where the two sites are located suggest that people abandoned the lowlands, during that period in favor of higher grounds, where vegetation has maintained equilibrium for the past 50,000 years. The stability of the highlands probably attracted people living in the region and probably forced them to adapt in a different environment.

Willoughby said she hopes her team's work will eventually determine if these findings paint a clearer picture of our African ancestors.

"It was only about 20 years ago that people recognized that modern Homo sapiens actually had an African ancestry, and everyone was focused on looking at early Homo sapiens in Europe who appeared around 40,000 years ago," she said in a statement. "But we now know that as far as back as around 200,000 years ago, Africa was inhabited by people who were already physically exactly like us today or really close to being the same as us. All of a sudden, it's not Europe in this time period that's really important, it's Africa."

If her team were to shift the narrative of the human diaspora, it would place a strong archeological emphasis on that region of Tanzania, a development that would be welcomed by the local people.

"They're telling me, 'You're putting Iringa on the map,'" she said. "As long as they keep letting me work there, and keep letting the people working with me work there, we'll be happy."