A high-tech study of tooth growth lines reveals that Neanderthals grew up faster than us, scientists report in the Proceedings of the National Academy of Sciences USA (PNAS) last week. Neanderthals had shorter childhoods and reached maturity earlier than modern humans.
Synchrotron images of Neanderthal child upper jaw showing the permanent teeth inside the bone (top image), and tiny growth lines inside the first molar teeth (lower image). © Graham Chedd (PBS), Paul Tafforeau (ESRF), and Tanya Smith (Harvard University and MPI-EVA)
Neanderthals were our closest relatives, disappearing about 30,000 years ago. They are usually regarded as a separate species, Homo neanderthalensis, and there has been a lot of debate about how close they were to us - modern humans or Homo sapiens.
This new research led by scientists at Harvard University, the Max Planck Institute of Evolutionary Biology and the European Synchrotron Radiation Facility, with Prof Chris Stringer at the Natural History Museum, highlights an important difference that may have given modern humans an evolutionary advantage over Neanderthals.
The international team compared the microscopic tooth growth patterns found in fossils from 11 Neanderthal and early modern humans, the largest sample of this kind studied to date.
The growth lines in teeth can be compared to tree rings, where yearly growth is visible in the rings left behind in the tree trunk, except they are laid down daily.
In primates, tooth growth lines reflect life events including age of weaning, first reproduction, and the death of a child (when line deposition ceases altogether).
Modern humans are unique among living primates in having earlier weaning, long childhoods and later age of reproducing. The great apes (chimps, gorillas and orangutans) wean later, reproduce earlier, and have longer intervals between births.
Tiny upper jaw (maxilla) of a Neanderthal child © Fossil courtesy of the Université de Liège
Using the latest X-ray technology at a synchrotron in Grenoble, France, the team produced highly detailed and accurate 3D images of the Neanderthal and early modern human teeth. They also compared the results with teeth from more than 300 modern people.
The team found that growth patterns in Neanderthal teeth corresponded to a shorter time period, meaning that they reached maturity distinctly earlier than modern humans.
And, when looking at early modern humans (from about 100,000 years ago), they found similar developmental times to those in recent humans.
These findings are consistent with other studies showing differences between Neanderthals and modern humans, such as the recent Neanderthal genetic code research, although that work also revealed evidence of some interbreeding between modern humans and the Neanderthals.
One of the fossils used in the study was a Neanderthal child from the Natural History Museum, which curator Robert Kruszynski transported to Grenoble for the research.
It was uncovered from Devil’s Tower in Gibraltar, and the child probably lived about 50,000 years ago.
Its age had previously been estimated at between 3 and 6 years old but the new study gave a more accurate age of 4 and a half years.