Humans wean babies from breast milk at a much younger age than our primate cousins, often years earlier. Very little was known about the breast-feeding habits of Neanderthals, however, until new information about their weaning habits was found in the study of a fossilized tooth.
Researchers from the U.S. and Australia have announced that they can now use the fossilized teeth of a Neanderthal to determine at what age the individual stopped breast feeding. Layers of barium in teeth act like tree rings, providing information on the age at which an individual was weaned.
"During the period of breast-feeding, the barium levels in teeth were higher," Manish Arora of the Icahn School of Medicine said. "At weaning, the levels of barium in teeth started to drop."
In at least one case, evidence seems to suggest that the individual whose tooth was examined was taken off breast milk at about the same age as modern humans, and not primates. The 100,000 year-old tooth from Belgium showed that the Neanderthal was fed exclusively breast milk for seven months, and then went through a supplementary period of another seven months before being completely weaned.
"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," Arora said.
The technique was developed from studies of teeth from both monkeys and humans. Katie Hinde, who directs the Comparative Lactation Laboratory at Harvard, spent three years studying the feeding and weaning habits of macaques. Such primates often spend many more years than the average human breast feeding their youngsters - Orangutan mothers will often wait seven years before taking their offspring completely off breast milk.
Our distant ancestors may have started weaning children at an earlier age in order to be able to breed more often, leading to more children.
Although researchers remain convinced of the accuracy of their research, other investigators contend that barium could have leached into the fossilized tooth.
Hinde and her team successfully tested her method with monkeys, and then moved on to humans and a Neanderthal tooth. Children were paid a small stipend for each baby tooth they donated to the research.
The findings were reported in the May 22 issue of the journal Nature.
