A new study published in the Proceedings of the National Academy of Sciences reveals that the modern human nursing strategy, with onset of weaning at 5 to 6 months, was present among Neanderthals who lived between 70,000 and 50,000 years ago in what is now Italy.
The extent to which Neanderthals differ from Homo sapiens is the focus of many studies in human evolution.
There is debate about their pace of growth and early-life metabolic constraints, both of which are still poorly understood.
“The beginning of weaning relates to physiology rather than to cultural factors,” said co-first author Dr. Alessia Nava, a researcher in the Department of Maxillo-Facial Sciences at Sapienza University of Rome and the Skeletal Biology Research Centre at the University of Kent.
“In modern humans, in fact, the first introduction of solid food occurs at around 6 months of age when the child needs a more energetic food supply, and it is shared by very different cultures and societies.”
“Now, we know that also Neanderthals started to wean their children when modern humans do.”
“In particular, compared to other primates, it is highly conceivable that the high energy demand of the growing human brain triggers the early introduction of solid foods in child diet,” said co-first author Dr. Federico Lugli, a researcher at the University of Bologna.
In the study, the scientists analyzed an unprecedented set of fossil teeth from archaeological sites in northeastern Italy.
These four milk teeth include three Neanderthals, dated to between 70,000 and 50,000 years ago, and one Early Upper Paleolithic modern human as a comparative specimen.
“Our results imply similar energy demands during early infancy and a close pace of growth between Homo sapiens and Neanderthals,” said co-senior author Dr. Stefano Benazzi, a researcher in the Department of Cultural Heritage at the University of Bologna and the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology.
“Taken together, these factors possibly suggest that Neanderthal newborns were of similar weight to modern human neonates, pointing to a likely similar gestational history and early-life ontogeny, and potentially shorter inter-birth interval.”
Using time-resolved strontium isotope analyses, the authors also collected data on the regional mobility of the Neanderthals.
“Neanderthals were less mobile than previously suggested by other scientists,” said co-senior author Dr. Wolfgang Müller, a researcher in the Institute of Geosciences and the Frankfurt Isotope and Element Research Center at Goethe University Frankfurt.
“The strontium isotope signature registered in their teeth indicates in fact that they have spent most of the time close to their home.”
“This reflects a very modern mental template and a likely thoughtful use of local resources.”
“Despite the general cooling during the period of interest, northeastern Italy has almost always been a place rich in food, ecological variability and caves, ultimately explaining the survival of Neanderthals in this region till about 45,000 years ago,” said co-senior author Dr. Marco Peresani, a researcher in the Institute of Environmental Geology and Geoengineering-IGAG CNR and the Department of Humanities at the University of Ferrara.
Alessia Nava et al. Early life of Neanderthals. PNAS, published online November 2, 2020; doi: 10.1073/pnas.2011765117
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