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Controversial Study Determines Weaning Age of a Neanderthal

May 24, 2013 02:29 PM EDT
This molar tooth model with the cut face shows color-coded barium patterns merging with a microscopic map of growth lines
Neanderthal babies may have been weaned from mother’s milk at about the same age as some modern day humans, according to a report from the California National Primate Research Center at the University of California, Davis.
(Photo : Ian Harrowell, Christine Austin and Manish Arora/graphic)

Neanderthal babies may have been weaned from mother's milk at about the same age as some modern day humans, according to a report from the California National Primate Research Center at the University of California, Davis.

A team of American and Australian researchers used barium samples in a fossilized molar of a Neanderthal child to calculate when the infant was weaned. Knowing that barium layers in primate teeth function as a historical record, much like rings in trees, the barium levels in a tooth reveal a timeline of eating and weaning habits, the researchers report.

By analyzing barium levels researchers concluded that the child was nourished exclusively by its mother's milk for the first seven months, and then switched to a diet of milk and other supplemental foods. After 1.2 years, the barium levels returned to prenatal levels, indicating a termination of breast feeding.

The researchers supplemented their analysis of the Neanderthal tooth with a sampling of lactation, weaning and behavior among rhesus macaques at the Primate Center.

Gleaning data from the three-year study of the macaques, the researchers were able to determine exact timing of birth, when the infant was fed exclusively on mother's milk, and the weaning process, from mineral traces in teeth. By studying monkey teeth and comparing them to center records, they could show that the technique was accurate almost to the day, the researchers report.

"Our studies on macaques and modern human children provide strong evidence that barium patterns in teeth do accurately reflect transitions from maternal milk to weaning,"said Manish Arora, a research team member from the University of Sydney, according to The New York Times.

While the barium dating research on modern day monkeys and humans seems accepted, the application of the barium dating technique on the Neanderthal tooth has garnered criticism.

Michael Richards, a specialist in ancient teeth and bones at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told The Times that the use of barium dating in archaeological samples fell out of practice in the 1970s because bone and teeth samples were found to have incorporated trace elements from the soil they were buried in and could not be relied upon as an indicator of diet. He said that he was surprised that the journal Nature published the study.

Another criticism of the study is that only one Neanderthal tooth was tested in the study.

But the researchers said their work is not over.

"By applying these new techniques to primate teeth in museum collections, we can more precisely assess maternal investment across individuals within species, as well as life history evolution among species," said Katie Hinde, professor of human evolutionary biology at Harvard University and an affiliate scientist at the UC Davis Primate Center.

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