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The whole tooth —
Winters were hard on young Neanderthals, reports a new study.
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 southeast France suggests that they endured colder winters and more pronounced differences between seasons than the region’s modern residents. The two Neanderthals in the study also experienced lead exposure during their early years, making them the earliest known instances of this exposure.
Hexbyte – Tech News – Ars Technica | Enduring harsh winters
Tooth enamel forms in thin layers, and those layers record the chemical traces of a person’s early life—from climate to nutrition to chemical exposures—a little like tree rings on a much smaller scale. Archaeologist Tanya Smith of Griffith University and her colleagues examined microscopic samples of tooth enamel from two Neanderthal children from the Payre site in southeastern France. The teeth were radiocarbon dated to around 250,000 years ago, and the set of samples recorded about three years of life.
One important clue to past environments 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 Payre Neanderthals, oxygen-18 ratios increased in the summer and dropped in the winter in predictable seasonal cycles, which Smith and her colleagues could compare from one week to the next. The data suggests harsher winters and more pronounced seasonal changes than today, and information about seasonal shifts can be combined with other details recorded in tooth and bone to explore how climate affected Neanderthals’ development and life histories. 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 stage,” wrote Smith and her colleagues.
The cold seasons were hard on Neanderthal children, because both of the ones from Payre bear lasting traces of illness or malnutrition during their early years. That kind of physiological strain impacts how the body absorbs and processes minerals, including the ones in tooth enamel, and that can leave a visible line across the tooth, marking the layers of enamel added during tough times. On a lower-left first molar from one child, Payre 6, the layers of enamel laid down during the late winter or early spring, not long before the child’s second birthday, show a line marking about a week of sickness or starvation. And another child, Payre 336, apparently suffered a similar two-week episode in the winter and anothe