Neanderthal teeth reveal lead exposure and difficult winters

A new study of oxygen isotope ratios and heavy metals in the tooth enamel of Neanderthals who lived and died 250,000 years ago in the south of France. The two Neanderthals in the study also experienced lead exposure during their early years, making the earliest known instances of this exposure.

Enduring harsh winters

Tooth enamel forms in thin layers, and those layers record the chemical traces of a person's early life-from a climate to nutrition to chemical exposures-a little like a tree on a much smaller scale. Archaeologist Tanya Smith of Griffith University and her colleagues in the field of microscopic samples of tooth enamel from two Neanderthal children from the Payre site in southeastern France. The teeth were radiocarbon dated around 250,000 years ago, and the set of samples recorded over three years of life.

One important clue to the past is oxygen, which comes from the water a person drank or the plants they ate. The ratio of the oxygen-18 isotope to oxygen-16 depends on temperature, precipitation, and evaporation. Generally, higher ratios of oxygen-18 indicate warmer, drier conditions with more evaporation.

In the Neanderthals Payroll, oxygen-18 ratios in the summer and predictable seasonal cycles, which Smith and her colleagues could compare from one week to the next. Neanderthals' development and life histories. The data suggests harsher winters and more pronounced seasonal changes than today, and information about seasonal shifts can be combined with other details Climate is often credited with driving hominin evolution, but it's rare that archaeologists can directly link the two.

"This is particularly germane for Neanderthals, who survived extreme Eurasian environmental variation and glaciations, mysteriously going extinct during a cool interglacial internship," wrote Smith and her colleagues.

The cold seasons were hard on Neanderthal children, because of both the symptoms and the symptoms of malnutrition during their early years. This kind of physiological strain impacts the body and processes of enamel, and it can leave a visible mark on the tooth, marking the layers of enamel added during tough times. We have a lower-left first molar from one child, Payre 6, the layers of late spring or early spring, not long before the child's second birthday, a week of sickness or starvation. And another child, Payre 336, apparently suffered a similar week-end in the winter and another week the next fall.

Other studies have noted that Neanderthal teeth often bear the lines left by these periods of hardship; According to Smith and her colleagues, many of these episodes probably occurred during the cold.

Oldest evidence of lead exposure

Heavy metals in the bloodstream, and the payment of 6 tooth tooth enamel. Around nine months of age, in the depths of winter, a band marks a sudden spike in lead exposure. A little over a year later, another band of concentrated lead marks at a sudden increase in exposure to late winter or early spring.

Payre 336 also seems to have been exposed to high levels of lead in the winter or late fall.

That's the oldest physical evidence of lead exposure archaeologists so uncovered so far, and it's probably a consequence of sheltering in cellars close to underground lead deposits. At least two lead mines within 25km (15.5 miles) of the Payre site, well within Neanderthals' likely foraging range. The early, constant lead exposure may have come from contaminated water or juice; Smith and her colleagues say that it would not be a good idea to have extra barium in enamel.

At around nine months, Payre 6 may have started to eat. The lead is not linked to the episodes of sickness or malnutrition, and it is impossible to know how it might have impacted these two children's health, but Smith and her colleagues note, "Decades of research are shown there is no safe level for lead in humans and other animals. "

A hint about demographics

Lead is not only heavy metal but finds its way into teeth. Nursing often leaves higher levels of barium in a child's tooth enamel. In Payre 6, enamel ugly, during the first nine months of life contains high levels of barium, but then it begins to tease off-lasting evidence of the moment to Neanderthal mother began weaning her child off milk and onto solid food. But that process lasted until the child was around 2.5 years old, when the barium signature in their enamel tooth finally fades out altogether.

That's about how long we live in the world, especially hunter-gatherer cultures whose lifestyles may resemble those of Payre 6 and his family.

This may eventually help in the puzzle of Neanderthal extinction. Populations that often live with these children, which means that people often do not grow faster than they do. For Neanderthals, trying to compete against Homo sapiens, population growth may have played a role, but it is too early to say for sure.

Payre 336's enamel tooth did not show any clear patterns of barium levels. The only other evidence of Neanderthal weaning is a 100,000-year-old tooth from Belgium, but instead of the gradual changes of weaning, its barium levels drop off abruptly around 1.2 years of age, as if the child had been separated from their mother . Smith and her colleagues say they need more information about when they are most likely to have their children compared to their children. Homo sapiens neighbors.

Science Advances, 2018. DOI: 10.1126 / science.eaau9483 (About DOIs).