Researchers have unearthed the graves of three Stone Age infants that may ultimately bear on the question of whether humans interbred with Neandertals. The rare find, from a 27,000-year-old site in Austria, includes two bodies that might be twins sheltered under a mammoth's shoulder blade.

The team discovered the skeletons in two separate burial pits: One uncovered last year contained two infants side by side--twins, apparently. A second pit containing a single body was found this year about a meter from the first pit. The twins had been protected from the elements by the mammoth bone and were very well preserved, says team member Christine Neugebauer-Maresch of the Prehistoric Commission of the Austrian Academy of Sciences in Vienna. An incisor from one of the pair indicates they died at nine or ten months of age, the group reports in the November 16 Nature. Before this, "there were no graves of newborns at all," Neugebauer-Maresch says. "We think if there are two preserved it's possible there are much more."

Numerous traces of burial practice survived. All of the infant remains were covered in red pigment, and more than 30 ivory beads lay near the pelvis of one of the presumed twins. The lone skeleton contained an ivory pin, which may have held shut a leather or fur wrapping, Neugebauer-Maresch says.

The excavators found the remains in an 18-square-meter site in lower Austria, near where the river Krems meets the Danube. The location contains a well preserved earthen floor and other artifacts characteristic of so-called Gravettian culture, including a fired piece of clay bearing a human fingerprint.

The infant burials were similar to those for Gravettian adults, whose remains often include mammoth bones and jewelry, says anthropologist Olga Soffer of the University of Illinois at Urbana-Champaign. "What is unusual is the extreme youth of these," she says. "Dead kids are few and far between, and the younger you get the fewer there are." The effort taken to bury and decorate the remains implies the infants or their families were held in high esteem, she notes.

Studying the Austrian infants or any DNA extracted from them may contribute to the debate over whether or not humans and Neandertals exchanged DNA, Soffer says. In recent weeks researchers have presented evidence that humans and Neandertals interbred when humans left Africa 30,000-40,000 years ago. Human skeletons found in Romania seem to show certain Neandertal traits, for example. The new remains could be examined for similar features, Soffer observes. "It will always be a little problematic because they're not mature, but it will be an important point of reference," she says. "There's lots and lots of exciting potential here."