Chemical analysis of 2-million-year-old teeth proves breastfeeding 6-year-olds was the norm for early humans.
While it’s uncommon for many modern Westerners to breastfeed for more than a year or two, a new study suggests the average age of weaning for early humans was five or six.
Anthropologists have previously speculated that the natural age of weaning is between 4 and 7 based on the behavior of other primates, but now we have more concrete evidence from the human fossil record.
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For the study, Australian archaeologists analyzed the chemical composition of fossilized teeth taken from two members of the species Australopithecus africanus, our distant human ancestors.
They mapped changes in the concentrations of barium, strontium and lithium in fossil teeth of two individuals.
The amounts of these elements in our bodies changes significantly depending on our diet, and the changes are recorded in the composition of our bones and teeth.
“Teeth are thus a perfect chemical time capsule of our childhood diet,” the authors of the study wrote.
The fossils were found in the UNESCO World Heritage Site known as “The Cradle of Humankind”, in South Africa, and are thought to be around 2 million years old.
The analysis the early humans breastfed exclusively for almost a year, and then supplemented with varying amounts of solid food until they were 5-6 years old.
“The balance between milk and solid food in this period varied cyclically, probably in response to seasonal changes in food availability,” the authors wrote.