You never know where you’ll end up when you set sail upon the Seas of Google.
My blog stats are capable of showing me what search engine terms people use to arrive here. “Mainstream parenting” is one of the most common; it seems there are more of us looking for support than I thought. Many also stumble upon the blog using the terms “congenital hypothyroidism” or “cretinism”, which brings them to this post (incidentally, I saw the little girl this morning, and she’s doing great on Synthroid). A close third in search terms is “the biological age of weaning” or some variant, leading – and hopefully educating! – people that it’s not at all what Kathryn Dettwyler claims it is.
But out of curiosity, when someone plugged that last search term into a search engine and arrived at this blog, I decided to do the same and see what comes up. As you can see, the first link is to here, but it was the second title that caught my eye: Stable Nitrogen Isotopes as Evidence for the Age of Weaning at the Angel Site: A Comparison of Isotopic and Demographic Measures of Weaning Age. The abstract doesn’t provide much information, and the full-text isn’t available for free online, but the concept seemed quite intriguing. An additional short Google and Pubmed search later, I found a wealth of sources discussing how and what is known about infants’ and young children’s diets in ancient cultures around the world. More specifically, how long they nursed back in the good old days.
It appears that one can use the different proportions of various nitrogen, carbon and oxygen isotopes in teeth and bones to determine the diet of a person, in infancy and at the age of death (i.e, plant-based, animal-based, or mixed). When you have the remains of a large population at the same site and of varying ages, you can estimate the age of weaning by looking at when the children’s bones showed a shift from a breastmilk-based diet to an adult food-based one according to the different isotope patterns in rib bones, which have a high rate of material turnover and reflect the proteins (the source of the nitrogen) ingested by the individual close to death. As infant mortality rates in the past were abysmally high, you can often find the bodies of babies and young children at such burial sites.
I found a bunch of studies done on various populations all over the world and at different historical periods which attempted to determine the weaning age in those population on the basis of stable isotope analysis. Here they are:
Stable Carbon and Nitrogen Isotope Values of Bone andTeeth Reflect Weaning Age at the Medieval Wharram Percy Site, Yorkshire, UK (10th-16th centuries): The researchers found that children were weaned at or before 2 years of age. This full-text article contains an excellent overview of the technique of isotope analysis.
Isotopic evidence for breastfeeding and possible adult dietary differences from Late/Sub-Roman Britain: Estimated complete cessation of breasfeeding at 3-4 years.
Trophic level and macronutrient shift effects associated with the weaning process in the Postclassic Maya: 2 sites in Belize, spanning the periods 100BC-1350CE, 1400-1650CE. Isotopic data indicate weaning started at 12 months and ended at 3-4 years of age.
Reconstructing infant weaning histories at Roman period Kellis, Egypt using stable isotope analysis of dentition: Weaning began at 6 months, ended by 3 years of age.
Weaning age among foragers at Matjes river rock shelter, South Africa, from stable nitrogen and carbon isotope analyses: A study of prehistoric bodies, also revealing a weaning age of 2-4 years of age.
Palaeodiet of Mesolithic and Neolithic populations of Meuse Basin (Belgium): evidence from stable isotopes: More prehistoric evidence of a weaning age of about 2 years old.
Fascinating. And let’s hear the end of the “noble savages” of yesteryear routinely breastfeeding their children until 6 or 7…please?