Scientists say skulls and tools help to date findings
A recent finding of human bones dating back 300,000 years calls into question the belief that modern humans evolved in East Africa, researchers say.
An international team of scientists has dated fossils found in Jebel Irhoud, about 90 kilometres northwest of Marakesh, Morocco, to be 300,000 years old — 100,000 years earlier than the previous specimens of Homo sapiens discovered in east Africa.
The scientists tout this as a significant finding, not just because of the age, but because of the location.
It's long been believed that East Africa was where modern humans evolved. But finding the specimens in northwest Africa challenges that idea.
"There is no Garden of Eden in Africa," Jean-Jacques Hublin, author of a paper published in Nature on Wednesday and director of the department of human evolution at the Max Planck Institute for Evolutionary Anthropology in Germany, told journalists at a briefing on Tuesday. "Or if there is a Garden of Eden, it's Africa."
Jebel Irhoud's fossils have a long history. Six fossils were first found at the site in the early 1960s during mining operations, including two skulls and a jaw bone.
But getting back to the site to further explore the area proved difficult for scientists, due to continued use of the land. However, in 2004, Hublin and his team were given permission to return and prepare the area for a dig, which started in 2005.
The view looking south of the Jebel Irhoud site in Morrocco. At the time the site was occupied by early hominins, it would have been a cave. Rock and sediment were removed by researchers at the site in the 1960s. (Shannon McPherron/MPI EVA Leipzig)
The dig yielded 16 more fossils. When the researchers assessed their findings, they discovered that they came from five separate individuals: three adults, a child and an adolescent.
The findings help answer a question that had plagued paleoanthropologists for years: Why did these fossils look more primitive than fossils dated from the same time?
Part of the dating technique the team used was thermoluminesence, a method that allows scientists to date material that was once heated. In this case, the team found flint that was likely heated as the early humans fashioned their Middle Stone Age tools.
The researchers are quick to note that these Homo sapiens aren't the same as the one that led to modern humans. However, there were similarities. Their faces were short, flat and retracted under the neurocranium, the upper and back part of the skull.
"It's the face of people you could cross in the street today," Hublin said.
Brain development into what modern humans have today would have taken place over tens of thousands of years.
A composite reconstruction of the earliest known Homo sapiens based on CT scans of multiple fossils. (Philipp Gunz/MPI EVA Leipzig)
"The story then is really of the last 300,000 years is really the story of the changes in the development of the brain," co-author Shannon McPherron, an archeologist at the institute told CBC News.
The researchers say that more study needs to be done to help us understand what was driving the change over hundreds of thousands of years, though this finding is the first step.
"It allowed us to envision a more complex picture for the emergence of our species, with different parts of the anatomy developing at different rates," Hublin said. "Some features being fixed very early in the modern way and others taking longer time to reach the modern conditions. The story of our species in the last 300,000 years is mostly the evolution of our brain."
"It's exciting ... because it's this idea of this pan-African process and development of the origins of our species, both behaviourally and biologically and we can now set that time beginning around 300,000 years ago," McPherron, said.
At the time our ancient ancestors were roaming northwest Africa there was a "green Sahara event," the researchers noted. This would have crossed the massive continent to East Africa.
"It makes perfect sense that early peoples would have been following the animals that they were hunting, which would have expanded into these green spaces, and so they would have found themselves occupying all of Africa," McPherron said.
In addition, the dig also shed light on the diet of early Homo sapiens. Bones of wildebeest, zebra and lion were found, but the most common was gazelle. There was even smaller game like hares, tortoises freshwater mollusks, snakes and ostrich egg shells.
Co-author Shara E. Bailey, an associate professor at the Department of Anthropology at New York University, told CBC News that she hopes this new finding will encourage paleontologists to look elsewhere for early hominins.
"It highlights the fact that we have to be wary of focusing on one area that is very well excavated and very well known," she said. "To me, it highlights what we don't know."