Neanderthals Grew Fast, but Sexual Maturity Came Late

Kate Ravilious
for National Geographic News
September 8, 2008
Live fast, die young—this is how our closest relatives the Neanderthals were traditionally thought to progress through life.

But a new study of Neanderthal skeletons suggests the species grew quickly but reached sexual maturity later than so-called modern humans—and quite possibly survived to a ripe old age.

(Related: "Neandertals Had Long Childhoods, Tooth Study Suggests" [September 20, 2005].)

The study also suggests that Neanderthals had a harder time of child bearing and possibly child raising. As a result, modern humans may have simply outbred their heavy-browed rivals.

By studying the skulls of Neanderthal babies, researchers were able to estimate how quickly the infants' brains grew.

They found that between birth and adulthood, a Neanderthal brain expanded faster than that of a modern human. The biggest growth spurt occurred in the first couple of years of life.

Neanderthal heads—and therefore brains—were already known to be larger than those of modern humans.

But that doesn't mean Neanderthals matured any faster.

"It shows that brain growth in modern humans and Neanderthals was quite similar and suggests that a fast pace of development was unlikely in the early years," said Chris Dean of University College London, who wasn't involved with the study.

The research appears tomorrow in the journal Proceedings of the National Academy of Sciences.

(For more on Neanderthals, watch Neanderthal Code, airing on Sunday, September 21, on the National Geographic Channel.)

Torturous Birth

Neanderthals first appeared in Europe about 300,000 years ago but mysteriously vanished about 35,000 years ago, shortly after the arrival of modern humans in Europe.

The University of Zurich's Marcia Ponce de León and colleagues pieced together three Neanderthal skeletons: one newborn from Mezmaiskaya Cave in Russia and two infants aged 19 and 24 months, respectively, from Dederiyeh Cave in Syria.

In addition, the scientists reconstructed the pelvis of an adult female Neanderthal skeleton, found in Tabun Cave in Israel.

(See a map of the Neanderthals' range.)

By analyzing the skeletons, the team found that Neanderthal babies were born with similar-size skulls to those of modern human babies. However, the shape of the face was different.

"Even in a newborn [Neanderthal] baby, we could see the conspicuous protrusion of the forehead that distinguishes Neanderthals," said study co-author Christoph Zollikofer, also of the University of Zurich.

By creating virtual reconstructions of the Neanderthal skeletons, the scientists also investigated the birthing process.

"The birth would have been at the limit of what was possible, and the baby's head would have had to turn by a quarter … in order to get through the narrow lower pelvis," Zollikofer said—as is required of the smaller-headed babies of modern humans.

Meaty Diet

Young Neanderthals' rapid growth required lots of energy, experts say.

"Neanderthals must have had a rich diet in protein and fat for children to fuel rapid growth in [their] brains," said Holly Smith of the Museum of Anthropology at the University of Michigan, who was not involved in the research.

Mothers also likely had to consume vast quantities of calories to produce enough breast milk.

This energy-intensive child rearing may have caused "somewhat longer interbirth intervals, or somewhat older mothers," study co-author Zollikofer said.

This may explain why modern humans eventually outcompeted Neanderthals.

(Read: "Neandertals Hunted as Well as Humans, Study Says" [January 25, 2006].)

"If one population reproduces just one percent more than another, then it can eventually replace the other population," Zollikofer said.

However, Dean of University College London is not convinced by this argument.

"I think they might be trying to push their data too far," he said.

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