Analysis of teeth suggests modern humans mature more slowly than Neanderthals did

Nov 15, 2010
A Neanderthal man ancestor's reconstruction. Neanderthal children grew up faster than humans, according a study Monday that suggested that modern kids' lengthy childhoods may be a relatively new phenomenon that has boosted our longevity.

A sophisticated new examination of teeth from 11 Neanderthal and early human fossils shows that modern humans are slower than our ancestors to reach full maturity. The finding suggests that our characteristically slow development and long childhood are recent and unique to our own species, and may have given early humans an evolutionary advantage over Neanderthals.

The research, led by scientists at Harvard University, the Max Planck Institute for Evolutionary Biology (MPI-EVA), and the European Synchrotron Radiation Facility (ESRF), is detailed in the .

"Teeth are remarkable time recorders, capturing each day of growth much like rings in trees reveal yearly progress," says Tanya M. Smith, assistant professor of human evolutionary biology at Harvard. "Even more impressive is the fact that our first molars contain a tiny 'birth certificate,' and finding this birth line allows scientists to calculate exactly how old a juvenile was when it died."

Compared to even , other primates have shorter gestation, faster childhood maturation, younger age at first reproduction, and a shorter overall lifespan. It's been unclear exactly when, in the 6 to 7 million years since our evolutionary split from non-human primates, the life course shifted.

Smith and her colleagues found that young Neanderthals' teeth growth -- a proxy for overall development -- was significantly faster than in our own species, including some of the earliest groups of to leave Africa some 90,000 to 100,000 years ago. This indicates that the elongation of childhood has been a relatively recent development.

State-of-the-art synchrotron imaging of the tiny upper jaw of a Neanderthal child allows scientists to count tiny growth lines inside the first molar teeth and determine that it died at age 3. Image: Fossil courtesy: Université de Ličge, Belgium; Photo credit: Graham Chedd, Paul Tafforeau, Tanya Smith

Such studies add to the growing body of evidence that subtle developmental differences exist between us and our Neanderthal cousins. The recent sequencing of the has provided tantalizing genetic clues pointing to differences in cranial and skeletal development between and modern humans.

The current study involves some of the most famous Neanderthal children ever discovered, including the first hominin fossil, discovered in Belgium in the winter of 1829-30. This individual was previously thought, based on comparisons with modern humans, to have been four to five years old at the time of death. Now, powerful synchrotron X-rays and biological rhythms inside teeth have revealed the child was only three years old.

While counting lines in teeth isn't a new method, Smith says, doing it "virtually" using synchrotron micro-computed tomography is.

"These new methods present a unique opportunity to assess the origins of a fundamentally human condition: the costly yet advantageous shift from a primitive 'live fast and die young' strategy to the 'live slow and grow old' strategy that has helped to make humans one of the most successful organisms on the planet," Smith says. Humans' extended maturation may have facilitated additional learning and complex cognition, possibly giving early Homo sapiens an advantage over their Neanderthal cousins.

Explore further: Scientists conclude sun-powered boat trip to find Europe's oldest village

More information: Smith, T.M., Tafforeau, et al. Dental evidence for ontogenetic differences between modern humans and Neanderthals, Proc. Natl. Acad. Sci. USA, November 15, 2010.

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RobertKarlStonjek
1 / 5 (1) Nov 15, 2010
Pygmies mature fast ~ they stop growing at 12 and typically have their first child by 16. So the Neanderthals are not quicker to mature than all modern humans...
see http://www.physor...722.html

Also of note is the error regarding the most successful organism, which are bacteria, viruses, single celled eukaryotes and many other microorganisms. In the mammals I'd say rats and mice are doing better than humans. Humans are the most successful primate.
Squirrel
5 / 5 (1) Nov 16, 2010
Actually, people called "pygmies" grow at the same rate as other people. To quote from the link given above “The pygmies grow in the same rates as the Turkana [eastern African Pastoralists], who also suffer from poor nutrition – but because the Turkana have longer life expectancy, they have time to grow for longer and achieve larger body size.

Squirrel
not rated yet Nov 16, 2010
The Smith et al paper is online with open access
http://www.pnas.o...full.pdf
jjoensuu
not rated yet Nov 16, 2010
So maybe their teeth just grew faster?
RobertKarlStonjek
1 / 5 (1) Nov 17, 2010
@Squirrel:
There is a difference between maturity and growth rates.
'Growth' describes the increase in body mass and the lengthening of limbs etc.
'Maturity' describes the completion of various stages of growth.
People can grow quickly or slowly and still reach maturity at the same age, but those who grow quicker will be taller.
Thus the pygmy, growing at normal rate, is shorter because they mature faster ie stop growing sooner than non-pygmies.
If two mature individuals are of the same hight but one of them matured earlier then that individual would also have had to have grown faster.

The paper indicates that Neanderthals both grew faster and matured earlier whereas the article above only mentioned earlier maturity.