Most interbreeding between Neanderthals and humans occurred around 50,000 years ago in the “Middle East” region between North Africa and Iraq, according to a new study.
Experts came to their conclusion after analyzing the facial structure of prehistoric skulls of 13 Neanderthals, 233 prehistoric Homo sapiens and 83 modern humans.
These had all been recovered from various locations in Asia, Europe and Africa.
The goal was to look for signs of Neanderthal influence on human facial anatomy that would result from interbreeding events.
“Neanderthals had big faces,” said Steven Churchill, co-author of the study and professor of evolutionary anthropology at Duke University.
“But size alone does not establish a genetic link between a human population and Neanderthal populations.
Discovery: Most interbreeding between humans and Neanderthals occurred around 50,000 years ago in the “Middle East” region between North Africa and Iraq, a new study says
“Our work here involved a more robust analysis of facial structures.”
Some of the ancient skulls showed such evidence of Neanderthal influence on human facial anatomy, leading researchers to pinpoint the Middle East as the region where most of the crossings occurred.
The sharing of this genetic material would have occurred 50,000 to 40,000 years ago, experts said, when modern Paleolithic humans lived at the same time and in the same regions as Neanderthals.
“Ancient DNA revolutionized the way we think about human evolution,” Churchill said.
“We often think of evolution as branches on a tree, and researchers have spent a lot of time tracing back the path that led to us, Homo sapiens.
“But we’re now beginning to understand that it’s not a tree, but rather a series of streams that converge and diverge at multiple points.”
Changes in facial shape and development may reflect changes in genetic makeup, and both occurred after early modern humans and Neanderthals interbred.
Experts came to their conclusion after analyzing the facial structure of prehistoric skulls of 13 Neanderthals, 233 prehistoric Homo sapiens and 83 modern humans. The facial feature locations for the measurements used in the study are shown above
The scientists compared measurements of similar facial features to see if there were signs of admixture in the ancient skulls they analyzed.
Other factors that may have led to changes were also considered to ensure that all identified revealing features could be definitively linked to the Paleolithic crossbreed.
“The picture is really complicated,” Churchill said. “We know there were crossroads. Modern Asian populations appear to have more Neanderthal DNA than modern European populations, which is odd – because Neanderthals lived in present-day Europe.
“This suggests that Neanderthals interbred with today’s modern humans when our prehistoric ancestors left Africa, but before they spread to Asia.
“Our goal in this study was to see what additional light we could shed by assessing the facial structure of prehistoric humans and Neanderthals.”
Ann Ross, corresponding author of the study and professor of biological sciences at North Carolina State University, said: “By evaluating facial morphology, we can track how populations have moved and interacted over time.
Some of the ancient skulls showed evidence of Neanderthal influence on human facial anatomy, leading researchers to pinpoint the Middle East as the region where most of the crossings occurred (pictured).
“And the evidence tells us that the Middle East was an important crossroads, both geographically and in the context of human evolution.”
She added: “We found that the facial features we focused on were not strongly influenced by climate, making it easier to identify likely genetic influences.
“We also found that face shape was a more useful variable for tracking the impact of Neanderthal interbreeding on human populations over time. Neanderthals were just bigger than humans.
“Over time, human faces became smaller in size, generations after they mated with Neanderthals. But the actual shape of some facial features still indicates admixture with Neanderthals.’
Churchill added, “The results we’ve had are really compelling.
“To build on that, we’d like to include measurements from more human populations, such as the Natufians, who inhabited the Mediterranean Sea in present-day Israel, Jordan and Syria more than 11,000 years ago.”
The study was published in the journal Biology.
WHAT KILLED THE NEANDERTHALS?
The first Homo sapiens reached Europe around 43,000 years ago and replaced the Neanderthals there around 3,000 years later.
There are many theories as to what led to the demise of the Neanderthals.
Experts have suggested that early humans may have brought tropical diseases from Africa that wiped out their ape-like cousins.
The first Homo sapiens reached Europe about 43,000 years ago and replaced the Neanderthals (model in the picture) about 3,000 years later
Others claim that falling temperatures due to climate change wiped out the Neanderthals.
The prevailing theory is that early humans exterminated the species through competition for food and habitat.
Homo sapiens’ superior brain power and hunting techniques meant Neanderthals couldn’t keep up.
Based on scans of Neanderthal skulls, a new theory suggests that the thick-browed hominids lacked key human brain regions vital to memory, reasoning and communication skills.
That would have affected their social and cognitive abilities – and could have killed them as they failed to adapt to climate change.