Winter in prehistoric southeastern France was brutal and the living was not easy for Neanderthal children. Their growth was constrained in the cold months, apparently by sheer illness, and on top of that they were exposed to lead, a groundbreaking analysis of their teeth has concluded.
“Decades of research have shown that there is no safe level for lead in humans and other animals,” the researchers observe in Science Advances.
The last half-million years have been marked by extreme swings between freezing glacial troughs and warmer periods, called interglacials. During one of these interglacials 250,000 years ago, as primitive pre-sapiens hominins reached Britain over land bridges, Neanderthals were thronging Payre, a site in the south of France.
Daytime and summer temperatures may have been balmy. But the winters were onerous and made the children, if not everyone, badly sick, archaeologists have concluded from the analysis of teeth from two Neanderthal minors.
The study published in Science Advances broke ground in analyzing prehistoric tooth enamel to reconstruct climate, chemical exposure and nutrition. They could do this because teeth, just like trees, have growth rings. During childhood a new layer forms every day, using the chemicals available in the body, the food and the air. Like tree rings, our teeth can tell a story about previous conditions during childhood development.
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Take oxygen, for instance: In warm weather, lighter oxygen-16 isotopes evaporate more readily than heavier oxygen-18. The enamel on our teeth builds up using the seasonally varying isotopes – so we can infer when a given layer was laid down.
Barium is another telltale mineral. Teeth from Homo sapiens kiddies and captive macaques, whose dietary history is known, have shown that barium distributions accurately reflect the transition from breast to solid food.
So: One of the French Neanderthal children seems to have nursed heavily for a year and a half, then to have been gradually weaned until eschewing the breast entirely at 2.5 years.
A separate study had tested a 100,000-year-old Neanderthal infant found in Belgium and concluded that it nursed for about a year and two months. But the Belgian baby did not have the hallmarks of gradual weaning (a progressive decline in enamel barium) like the French children did. The Belgian baby seems to have abruptly been transferred to solid foods, so the Payre child seems more indicative of the Neanderthal norm.
In that, modern humans seem akin to Neanderthals. Preindustrial modern humans also nursed the kids for about two and a half years, says the paper, which was written by an international research team with biological anthropologists, archaeologists, earth scientists and environmental exposure experts.
Despite the theories that Neanderthals were spectacularly evolved for the cold, in fact, they didn’t live in particularly cold areas – and the story of the Neanderthal children’s teeth suggests that they got horribly sick, and/or starved. One of the children suffered heightened skeletal remineralization during the heart of winter, a hallmark of extreme weight loss.
The lead exposure wouldn’t have caused defects in enamel layering that the scientists found. But severe illness could.
Also, the exposures to lead were both brief and clearly associated with cold weather. Either that or the Neanderthals consumed contaminated food or water, which can happen; or they inhaled lead molecules from fires. (It has not been proven that Neanderthals knew how to make fire purposely, but they did know how to utilize it.)
“Traditionally, people thought lead exposure occurred in populations only after industrialization. But these results show it happened prehistorically, before lead had been widely released into the environment,” said one of the study’s lead authors, Dr. Christine Austin, assistant professor at the Icahn School of Medicine at Mount Sinai.
The isotope analysis of the enamel layers also led to the postulation that at least one baby had been born in spring – a time in which many a mammal procreates because the living is easy, and so on.
The team also deduced that both kids did badly in winter. They got sick. One had a marked developmental defect in the enamel that persisted for a week, during the height of winter. The other had two defects, created in winter and fall.
The researchers admit their study size of two is a tad small to make generalizations, but the results are intriguing.
Separate research has indicated that in contrast to our direst suspicions, humans didn't kill off the Neanderthals. It was, after all, climate change leading to cold drought, and at most, we moved into the caves they vacated with their demise.
Some 248,000 years after the Neanderthals lived in France and breathed or ate lead, the same metal would be speculatively fingered as a cause for the collapse of the Roman Empire. Not realizing its toxic properties, the ancient Romans not only made face powder from it, but medicines and water pipes – efficiently poisoning themselves, the theory goes. It remains to be proven that the lead was a key cause. Meanwhile, the levels to which these French Neanderthals were naturally exposed were much lower, yet still discernible.