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Neanderthal toothy grin was just like ours

Neanderthal tooth

Neanderthal tooth with small horizontal lines, called perikymata, covering the surface. The distance between each line represents how fast the tooth enamel has grown in about 8 days (Image: OSU/Debbie Guatelli-Steinberg)

Modern humans and Neanderthals may have had childhoods of similar length, according to new research that focuses on tooth development as a marker for properties of growth and ageing.

While Neanderthals, who went extinct 30,000 years ago, have been portrayed as homely, doltish beings, the findings suggest that they may have been more like humans than one thought.

Teeth provide clues because dental and body development are closely linked. For example, teeth must erupt before weaning and molars can only erupt when the jaw becomes large enough to accommodate them.

Neanderthal tooth development followed a similar growth course as that for modern humans, according to scientists who looked at front teeth belonging to both groups under powerful microscopes.

"Like trees, teeth grow in layers," says Professor Debbie Guatelli-Steinberg, who led the study.

"These layers, which are analogous to tree rings, are visible under a microscope and they represent anywhere from six to 12 days' worth of growth in humans. By counting these layers, one can estimate how long it takes for the enamel surface to form."

The researchers compared the dental growth rate for Neanderthals with that of three modern groups of humans: Inuit, English and southern African.

All shared similar periods of tooth development, according to the study, which is published online today in the journal Proceedings of the National Academy of Sciences.

"It is clear that Neanderthals were growing their teeth in comparable or even longer periods of time than some of the modern human populations we studied," says Guatelli-Steinberg, an Ohio State University anthropologist.

Since teeth can serve as a growth chart for individuals, she and her colleagues believe that Neanderthals may have had prolonged childhoods, like modern humans.

The Neanderthal brain also seems to have been relatively big and heavy, similar to modern humans', as prior research correlated brain weight with molar eruption times.

Christopher Dean, a professor of anatomy and developmental biology at University College London, says the new research furthers our knowledge of Neanderthal tooth development.

But he hopes future studies will reveal more specifics, such as how Neanderthal teeth roots grew.

Assistant Professor Gary Schwartz, an Arizona State University anthropologist, says the study provides "extremely compelling evidence that the time it took Neanderthals to grow their teeth is broadly similar to that for modern human populations".

He says while Neanderthal adults looked different from us in many ways, these differences might have emerged because "Neanderthals were a highly-specialised, highly-successful population of fossil human ancestors living, for the most part, during very harsh, glacial times".

Both he and Guatelli-Steinberg indicate it is still too early to say that similar tooth development and comparable overall body growth rates could mean that Neanderthals were in any way related to us.

"If Neanderthal maturation was comparable to those of modern humans, this still doesn't mean anything about how closely related Neanderthals are to modern humans," Guatelli-Steinberg says.

"It is entirely possible to have two different species with similar maturation periods."

Tags: archaeology, palaeontology