A baby Neanderthal who lived in what is now Belgium about 100,000 years ago started eating solid food at 7 months old, revealing a new aspect of the evolution of breast-feeding. A new technique that uses elements in teeth helped researchers to determine when breast-feeding started and stopped.
     "Breast-feeding is a major determinate of child health and immune protection, so it's important both from the point of view of studying our evolution as well as studying health in modern humans," study researcher Manish Arora, a research associate at Harvard's School of Public Health, said.
     Until now, however, no one had an effective way of looking at bones and reconstructing breast-feeding history. Arora and his colleagues found that both in humans and macaques, the ratio of the elements barium and calcium in the teeth revealed what the baby had been eating when those teeth formed. The parts of the teeth that form in the gums before birth have very little barium, Arora said, probably because only a small amount of the element gets into the fetus through the placenta. After birth, barium spikes and stays high in the tooth; the profile changes again when babies (or macaques) start adding solid food to their diet of breast milk. "You find the amount of barium we can absorb from solid foods such as vegetables and meats is different from what we get from breast milk, so we can see this period of exclusive breast-feeding," Arora said.
     Arora and his colleagues tested their new method on a very old tooth. They used a molar from the Scladina Neanderthal, a fossilized juvenile found in Belgium. Similar patterns as in humans and macaques appeared: a barium increase at birth, which stayed high until the Neanderthal was about 7 months old. At that point, the tooth indicated, the Neanderthal baby went into a transitional diet, consuming breast milk supplemented by solid food. The pattern is one that today's parenting experts would likely approve.
     The Neanderthal's mixed diet continued for seven months until 14 months of age, when the baby abruptly weaned. No one knows what happened, Arora said. It's possible the Neanderthal became separated from its mother, or perhaps the mother got pregnant or gave birth to a younger sibling and cut her older child off from the breast.
     So far, Arora and his colleagues have tested only the Scladina Neanderthal, and they aren't sure whether its weaning pattern is typical of the species. "We would very much like to do this on more Neanderthal samples and even beyond Neanderthal samples, on other extinct primates leading up to modern humans," Arora said. The goal would be to create an evolutionary map of breast-feeding practices in primates, he said. This line of research could also reveal insights into the long-term health effects of breast-feeding.

Edited from LiveScience (22 May 2013)