Neanderthal toddlers grew faster than their modern human counterparts, likely as an adaptation to living in a cold, harsh environment, new research suggests.

The discovery, which was made using the bones of a young Neanderthal discovered in Amud Cave in northern Israel in the 1990s, suggests that Neanderthals and modern humans (Homo sapiens) followed different evolutionary paths after they split from a common ancestor around 600,000 years ago, the researchers reported April 15 in the journal Current Biology.

The Amud 7 skeleton was found in more than 100 pieces, which included fragments of the child's arms, legs, chest and skull, all of which displayed distinctively Neanderthal anatomical features even at the child's young age. However, because Neanderthal infant skeletons are rarely found, the actual age at death of Amud 7 has been difficult for researchers to pin down.

Archaeologists typically estimate an ancient child's age based on the growth and eruption of teeth and on the size and completeness of various bones. The growth curves for the bones and teeth of modern human babies are well documented, but Amud 7 has revealed that at least one of the Neanderthals' growth stages was much faster than modern humans'.

"The results of this study suggest that the growth trajectory of young Neandertal infants may have differed from that of H. sapiens," the researchers wrote in the study. Specifically, Neanderthal babies' bodies developed more rapidly than modern humans' did in the first years of life but then evened out during later childhood. "This suggests an evolutionary strategy emphasizing accelerated development in the early years of life, likely advantageous in the harsh environments Neandertals inhabited," the researchers wrote.

Although this new analysis of the Amud 7 skeleton reveals important information about Neanderthal children's growth and development, the researchers cautioned that more data is needed from other non-adult Neanderthal skeletons. They noted that a larger sample size may shed light on whether this pattern was widespread or a specific ecological adaptation.

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Kristina Killgrove is a staff writer at Live Science with a focus on archaeology and paleoanthropology news. Her articles have also appeared in venues such as Forbes, Smithsonian, and Mental Floss. Kristina holds a Ph.D. in biological anthropology and an M.A. in classical archaeology from the University of North Carolina, as well as a B.A. in Latin from the University of Virginia, and she was formerly a university professor and researcher. She has received awards from the Society for American Archaeology and the American Anthropological Association for her science writing.