Like all mammals, the Neanderthals breast-fed their babies. Scientists wanted to know: For how long?
Today in Nature, a team of researchers, including several from UC Berkeley, say they’ve answered that question by looking at the fossilized tooth of an eight-year old Neanderthal child, discovered in a Belgian cave.
Asa Bradman is an environmental health scientist at UC Berkeley and a co-author on the paper. He says teeth are like a time capsule.
“Because teeth grow in rings, kind of like trees do, you can actually date when a given layer of the tooth was put down.”
Breast milk is high in barium, which crystalizes in teeth, even before they emerge from a baby's gum line.
Bradman, UC Berkeley’s Brenda Eskenazi, and others on the team hypothesized that if they could learn how barium deposits correspond with age, they might reveal the breast-feeding histories of our distant cousins the Neanderthals, who roamed Europe 30,000 to 300,000 years ago.
But first, they had to establish that their methodology worked. So, they tried it out with humans: a group of pregnant women recruited in Salinas, California as part of the Health Assessment of Mothers and Children Study.
Twice during pregnancy and at six-month intervals after birth, researchers asked the mothers whether they were using breast milk or formula, and noted the age at which mothers introduced food to their children.
Years later, when the kids started to lose their teeth, researchers brought those teeth in for lab analysis, to see how barium levels corresponded to breast feeding histories.
They did the same thing with macaque monkeys living at UC Davis.
Analysis of both species showed a clear breakdown of when barium levels were highest – i.e, during periods of exclusive breast feeding – and when they returned to “baseline” levels, after the child had weaned.
“In the tooth,” says Bradman, “we can actually see a fingerprint, so to speak, of the milk intake during the life of the child.”
In Australia, a team of scientists analyzed the fossilized tooth of an eight-year old Neanderthal child, some 100 thousand years old, found in Belgium’s Scladina cave.
“The child was exclusively breastfed for about seven months and then continued to breastfeed up until 14 months,” says Bradman.
“It’s remarkably similar to the recommendations by the American Academy of Pediatrics for modern humans.”
For more on this story, See Adam Cole's excellent article on npr.org.