Presumably, the first Homo sapiens brooded their offspring longer than the Neanderthals, which perhaps contributed to their better survival, paleoanthropologists argue in an article which appears Thursday in Scientific Reports.
These researchers from the University of Tübingen, Germany, examined the tooth enamel of Neanderthals and Homo sapiens from the Upper Paleolithic, and noted any abnormalities (furrows, grooves, holes) resulting from hypoplasia — disease which occurs during the development of enamel and which disrupts its formation — which they presented. Knowing that these anomalies are indicators of stress experienced during the period of child development, they were able to compare the intensity of stress experienced by young children from the two groups of hominids, as well as the particular times when they experienced it. suffered.
Covering 423 teeth from 74 Neanderthals and 444 teeth from 102 modern humans from the Upper Paleolithic (between 50,000 and 12,000 years ago) found on a total of 56 different sites, their analysis of the occurrence of dental enamel anomalies showed that both groups faced comparable levels of physiological stress during childhood. The latter could take the form of “malnutrition, nutritional deficiencies, diseases, infections, or trauma”.
This observation contradicts a long-held hypothesis according to which Neanderthals led a much more stressful life than Homo sapiens, in particular because of harsh and fluctuating environmental conditions, which would have contributed to their extinction.
Given the sequential development of the different types of permanent teeth (molars appearing before the incisors, which are followed by the canines, then by the premolars and the second molars), the identification of those which bore marks of hypoplasia made it possible to highlight times when the child had experienced episodes of stress. It first appeared that in both groups, the milk teeth presented very few hypoplastic defects, much less than the permanent teeth. To explain this phenomenon, researchers hypothesize that perhaps the enamel of these milk teeth would be less subject to hypoplasia or that these teeth would form in the fetal environment which protects it from stress.
Later episodes of stress
On the other hand, in modern humans, it was mainly the incisors and molars that were affected, while in Neanderthals, it was mainly the canines, premolars and second molars, teeth which erupted later. These observations therefore reflect the later occurrence of stress episodes in Neanderthals than in modern humans.
According to the authors of the study, anomalies in the development of enamel in Homo sapiens mainly occurred during weaning of children, which is a very stressful period for them. “During the weaning process which extends from the age of six months, when the first solid foods are introduced, to two and a half years, the average age at which weaning is completed, the child’s energy needs growing amounts and must be satisfied by adding food to breast milk, otherwise insufficient nutrition at this time can lead to malnutrition, chronic digestive problems and a higher risk of disease, all situations which can cause significant metabolic stress, disruption of growth and, thereby, increasing hypoplasia of dental enamel,” emphasize the researchers.
In Neanderthals, episodes of intense stress occurred a little later.
“Although the weaning period was stressful for both groups, the post-weaning period was even more stressful for the Neanderthal children, while this is not the case for the children of Homo sapiens,” the researchers said by email. principal investigators of the study, Sireen El Zaatari and Laura Limmer.
According to the authors of the article, these observations suggest that Upper Paleolithic humans adopted “social and behavioral strategies to provide sufficient energy-rich food following weaning in order to reduce stress.” in young children: they prolonged their dependence on their parents, they still provided them with good access to food and they exploited resources more efficiently. These strategies, which were probably not used by Neanderthals, may have helped ensure better long-term survival for modern humans.”
Difficult comparison
Antoine Balzeau, researcher at the National Museum of Natural History and the National Center for Scientific Research (CNRS), does not immediately corroborate this interpretation on “the possible modes of behavior and the advantage that they could give to Homo sapiens » proposed by the authors of the study.
But he praises the quality and originality of the study and describes the results as very interesting and new. “It’s a nice work on abundant material and numerous specimens. The main result showing a difference [temporelle dans la présence de stress] between the two groups, that once weaning was completed, Homo sapiens would have experienced less stress than Neanderthals, is super interesting and new. Interpret it as a better way to manage children [pour Homo sapiens, qui aurait conduit à] better evolutionary success is delicate and difficult to demonstrate, especially since the Neanderthal sample spans tens of thousands of years, while that of Homo sapiens spans only a few thousand years. The two groups of samples are difficult to compare,” he comments.
But isn’t it likely that Homo sapiens brooded its young more? “It’s likely, why not, but being able to demonstrate it on the basis of scientific data is extremely complex. It seems logical and expected, but you have to be careful when you are in disciplines where you have little information. What is logical in science is not necessarily what is right. [L’interprétation] does not shock me, why not, but the most important thing is the results they obtain which are solid and interesting,” concludes the researcher.