Study sheds light on divergence of Neanderthals and humans

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Last week, a team of scientists published new findings indicating that the divergence between Neanderthals and modern humans occurred more recently than previously thought.

Scientists from various institutions, including the Berkeley Geochronology Center, re-examined 17 craniums from the Sima de los Hueso, or “Pit of the Bones,” site in Atapuerca, Spain for a study published Thursday in the journal Science. The study identified the skulls as belonging to early members of the Neanderthal lineage rather than the species Homo heidelbergensis. It also provided researchers with a new date for the skulls — 430,000 years ago, instead of 530,000 years ago.

Juan Luis Arsuaga Ferreras, who led the excavation of the skulls, said these are the oldest specimens found at the excavation site. Arsuaga explained that the skulls did not belong to Neanderthals but exhibit Neanderthal traits in the facial skeleton and jaw, along with more ancient morphologies.

“This is a gold mine. Never before have 17 skulls been discovered together in a single site,” he said in an email. “It is like traveling to the past and meeting a family of ‘archaics.’ ”

This new information comes from modern dating techniques, including U-series dating, in which scientists measured limestone deposits within the Sima cave, such as a concretion found on a specific skull. As another way of dating, researchers also examined mud layers above the fossils.

“We have confirmation from these two distinct and quite independent dating techniques showing an age of about 430,000 years for these fossils,” said Warren Sharp, a geologist from the geochronology center.

The study’s findings also indicate a later divergence of the Neanderthal and homo sapiens lineage than previously thought, according to Chris Stringer, an anthropologist at London’s Natural History Museum, who was not involved in the study.

There has been much controversy within the scientific community regarding exactly when Neanderthals and modern humans diverged from their common ancestor during the Middle Pleistocene time period, about 130,000 to 780,000 years ago.

According to Jean-Jacques Hublin, a professor at the Max Planck Institute for Evolutionary Anthropology in Germany, the new study confirms the “accretion model” he proposed. The model holds that Neanderthal features did not appear together as a package but accumulated through time as a result of the expansion and contraction of ancient European populations.

Hublin wrote an article in Science explaining how the recent findings concur with his model, although he did not help author the study.

“The new dating of Sima de los Huesos precisely anchors the origin of the Neandertals in a remote past,” he said in an email. “This age will represent an important landmark for further paleontological and genetic studies.”

Contact Brennan MacLean at [email protected] and follow him on Twitter @brennan_mac.