The team’s findings, which will appear in the Sept. 25th issue of the journal Proceedings of the National Academy of Sciences (PNAS), extend the record of early people taking care of other community members as far back as 175,000 years ago. The article will be posted on the PNAS Web site at www.pnas.org on Sept. 11.
The fossils, from three different humans estimated to be about 175,000 years old (from the Middle Pleistocene period), show a stage of evolutionary development that led to the Neandertals that appeared in Europe between 50,000 to 100,000 years ago. Serge Lebel, Ph.D., associate professor in the earth sciences department at the University of Quebec in Montreal, led the team that found the fossils in the Bau de l’Aubesier, a large rockshelter in Monieux, Vaucluse, France.
As humans spread across the Old World, they acquired regional patterns of anatomy, and the fossil jaw — one of the few found from this period — shows evidence of the gradual accumulation of Neandertal features in this group of humans, say the researchers from Canada, the United States, France and Germany.
From the shape of the jaw fragment, scientists can see that the cheek was beginning to sweep back, demonstrating that the face was losing strength. Because of the changing patterns of food preparation, less forceful mastication was needed. That finding reinforces concepts derived from examining the otherwise limited fossil record.
But the jaw also has changed perceptions about early human behavior, specifically when the early humans began to care for, and support, people within their groups who had difficulty caring for themselves.
Previous fossils have shown evidence of caring for infants with congenital problems in the Middle Pleistocene, but the jaw provides the first evidence of long-term survival of someone without effective chewing. Because of massive periodontal inflammation, all of the teeth had been missing or ineffective for some time before the individual died. Previous evidence for such survival was about 50,000 years ago, 125,000 years later than this study documents.
"This is the oldest example of someone surviving for some period of time without an effective set of choppers," Trinkaus said. "There had to have been extensive preparation of food — a combination of cutting and cooking — before this person could eat. They had good cutting tools and controlled fire, but the absence of real hearths and tools that would have done more than dice the food suggests that this individual was being given softer food items by other members of the social group.
"Although commonplace among later Neandertals and recent humans, such survival of toothless humans is unknown for earlier time periods," Trinkaus added.
Editor’s note: For a copy of the PNAS article, contact the PNAS news office at 202-334-2138 or firstname.lastname@example.org.
Photographs of the fossils are available in tif format by contacting Erik Trinkaus (email@example.com).
Proceedings of the National Academy of Sciences