Researchers report a tooth study takes a bite out of the idea that modern humans are related to Neanderthals. An extinct branch of humanity, Neanderthals lived in Europe as recently as 30,000 years ago. Whether modern humans, slimmer with slightly smaller brains, are their descendants is hotly debated by paleontologists.
In the journal Nature, international scientists led by Fernando Rozzi of CNRS, a Paris-based research institute, report on their analysis of several hundred fossil front teeth from early humans, Neanderthals and modern humans.
Surprisingly, tooth enamel patterns suggest that Neanderthals grew to adult size by age 15, sooner than mankind's more prehistoric precursors and more similar to the development of apes. The researchers call this an "evolutionary reversal" that points to strong differences between Neanderthals and modern humans.
Modern humans moved into Europe at about the same time Neanderthals started to disappear. Differences in the development of tools, climate changes or even conflicts between the two species have been suggested as reasons for the Neanderthals' disappearance after several hundred thousand years of existence, reports usatoday.com
According to startribune.com when you're living on the edge of a largely ice-covered continent, sleeping in caves, sharing turf with giant cave lions and bears, you had better grow up quickly. A new study of teeth shows that Neanderthal children did just that, reaching maturity by about 15 years of age.
Among all other human ancestors right down to modern humans, the trend had been for dental growth to slow with aging, a marker for later overall development and maturity. But among Neanderthals, teeth grew at a fairly constant rate, with other research showing individuals as young as 4 or 5 sporting teeth suitable for the hunting and foraging life.
The authors of the new study said Neanderthals, who had larger brains than modern humans, must have had a high-calorie diet and a fast metabolism to fuel such rapid growth in a particularly harsh environment.
Neanderthal remains discovered in Europe and the Middle East over the past 150 years point to a young crowd - clans of 30 to 50 individuals made up mostly of children and juveniles, with women rarely surviving much past age 30, and men seldom seeing age 40.
"Neanderthals were characterized by having the shortest period of dental growth," said Ramirez Rozzi. Whether Neanderthals evolved gradually into modern humans or were displaced or killed off by them is a question still being debated by scientists. Some researchers believe there may have been interbreeding to some degree.
Neanderthals lived in caves or huts, used fires and tools and ate a variety of animals. They may have been cannibals and could have communicated with speech.
Jan Kelley, of the University of Illinois in Chicago, said in a commentary in the journal that more studies on teeth fossils are needed to support the conclusions reached by Ramirez Rozzi and Bermudez de Castro.
"Nonetheless, these authors have opened up what should prove to be a fruitful line of research into both the relationships and the palaeobiology of Neanderthals," Kelley said, inform reuters.com