Neanderthals’ lives were historically portrayed as highly stressful, shaped by constant pressures to survive in harsh ecological conditions, thus potentially contributing to their extinction. In new research, paleoanthropologists analyzed the frequency of dental enamel hypoplasia, a growth disruption indicator of early life stress, in the largest sample of Neanderthals and Upper Paleolithic humans. Their findings support similar overall stress levels in both groups but reveal species-specific patterns in its ontogenetic distribution: while Neanderthal children faced increasing likelihoods of growth disruptions starting with the weaning process and culminating in intensity post-weaning, growth disruptions in Upper Paleolithic children were found to be limited around the period of weaning and substantially dropping after its expected completion. These results might reflect differences in childcare or other behavioral strategies between the two species, including those that were advantageous for modern humans’ long-term survival.
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Neanderthal family. Image credit: Field Museum.
“Neanderthals have been traditionally portrayed as having led exceptionally stressful lives including the pressure to survive in the harsh and widely fluctuating ecological conditions of Pleistocene Eurasia, which was thought to have contributed to their extinction,” said Dr. Laura Limmer from the University of Tübingen and her colleagues.
“Even though Upper Paleolithic modern humans also faced similar environmental conditions, they are commonly believed to have been better able to mitigate such pressures through their behavioral repertoire.”
“This included strategies such as greater flexibility and efficiency in resource exploitation and more complex social organization and networks.”
“Their behavioral repertoire was thought to have provided Upper Paleolithic modern humans with a competitive advantage over Neanderthals, allowing them to persist while Neanderthals perished.”
“Some recent studies, however, are casting doubt on this view, arguing instead that Neanderthals and Upper Paleolithic modern humans led similarly stressful lives.”
For the study, the researchers analyzed the dental enamel of 423 Neanderthal teeth and 444 Upper Paleolithic humans.
They investigated early-life stress in these individuals by identifying horizontal grooves of thinner enamel, which previous research has demonstrated can be associated with childhood stressors such as illness, infections, malnutrition, nutritional deficiencies, and trauma.
They found that the overall likelihood of enamel defects was similar in both Neanderthal and Upper Paleolithic modern human teeth.
“We did however observe differences in the distribution of the dental enamel defects over the development stages: in modern humans, enamel defects were more likely to occur within the timeframe when the children were being weaned,” Dr. Limmer said.
Among Upper Paleolithic humans, enamel defects were more likely to occur around the ages weaning is estimated to have occurred — between one and three years of age — than after the estimated weaning period.
Among Neanderthals, enamel defects were more likely to begin to appear with the expected weaning period (around one year of age), before peaking during the post-weaning period (between two and four years of age) and then decreasing.
The scientists hypothesize that the stress experienced by Upper Paleolithic human children during weaning could have been caused by increasing energy demands raising the risk of malnutrition.
They propose that Upper Paleolithic humans may have helped reduce developmental stress in children after weaning through strategies such as encouraging prolonged dependence on parents, exploiting resources more efficiently, and providing children with access to food.
They suggest that these strategies may not have been used by Neanderthals and that this could have contributed to long-term survival advantages for modern humans compared to Neanderthals.
“It’s possible that modern humans gained an advantage over the Neanderthals through supporting their children better in this difficult phase, for instance by protecting the children for longer and a better supply of food,” said Dr. Sireen El Zaatari, a researcher at the University of Tübingen.
“It’s often stated that Neanderthals lived in an especially harsh climate with low temperatures and that this led to them perishing.”
“Yet for a certain period Neanderthals and modern humans were subjected to the same climatic conditions, therefore we are researching other explanations.”
The study appears in the journal Scientific Reports.
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L.S. Limmer et al. 2024. Differences in childhood stress between Neanderthals and early modern humans as reflected by dental enamel growth disruptions. Sci Rep 14, 11293; doi: 10.1038/s41598-024-61321-x
