Human growth and development, from the earliest phases of ontogenesis, is affected by dietary behaviour, including that of the mother during pregnancy.
From an historical perspective, the study of the strong connections among diet, adaptation, and culture, particularly during infancy and gestation, can offer an invaluable contribution for the reconstruction of the past societies. Indeed, the adoption of farming economies between the Early Holocene and the 4th millennium BCE was probably the greatest innovation in human history. As the new farmers, their ideas, and the new economies spread across space and time it led to altered social behaviours and changes to human biology. The new social structures that emerged laid the foundations for ancient urban societies and continue to influence the way that we live today. One of the pivotal moments of everyone life, i.e. weaning, was woven into these changes.
Indeed, gestation and breastfeeding are substantial energetic investments for the mothers and are constrained by access to food resources. The first introduction of foodstuffs in an infant’s diet – i.e. the onset of weaning – is pivotal in shaping the growth and health of infants. Weaning age directly reflects the way infants are cared for within a human society. It is linked to female fertility, maternal and non-maternal care strategies, social stratification, infant growth, and even adult health. Weaning age continues to be relevant for present day populations through policies issued by the World Health Organization. Yet, we know almost nothing about the way weaning age developed during recent human evolution.
The goal in this project was to reconstruct weaning age in extensive collections of human skeletons that span periods of transitions during recent human evolution. WEAN-IT uses a recent methodological development to trace elemental composition in dental enamel to identify the change from an exclusively breast milk diet to one that includes non-milk foods. The results derived from the integration of microstructural, histological, and chemical signals of weaning in milk teeth. Indeed, dental remains provide direct evidence of the initial infancy of humans at very high time resolution and carry the morpho-chemical signals of diet (including weaning), health, mobility, biorhythms, and the pace of growth from birth until the first years of life.
The overall objectives are: 1) to Identify the timing of weaning in modern human samples as a comparative benchmark for the ancient ones, 2) to determine the timing of weaning in archaeological skeletal populations, 3) to explore growth during weaning in both samples; and 4) to elucidate the social correlates of the changes in the timing of weaning.
Results of WEAN-IT, disseminated through many open-access articles and conferences, show - and will show in future publication - the feasibility and the importance of the project, highlighting a rather conservative, possibly biologically constrained, onset of weaning even in extinct human forms (Neanderthals) contrasting with a high variability of weanling food through time. This project adds value and competitiveness to the bioarchaeological research landscape in Europe, thanks to its innovative multi-methodological approach. Not only WEAN-IT is of interest to a broad range of academics within the social sciences, but it can inform present day public health policy as I will directly measure the effect of weaning on bone growth.
