About 49,000 years ago, a Neanderthal boy died young. The cause of death isn’t clear. Scientists who pored over his bones many millennia later found no signs of fatal trauma or disease. But something cut his life abruptly short about four months shy of his eighth birthday.

He left behind a remarkably complete skeleton. The Neanderthal bones tell a story of a species that grew slowly through early childhood, a team of scientists reported in the journal Science on Thursday. That story, they say, is quite like our own.

“What we see in this Neanderthal is the general pattern of growth is very similar to that of modern humans,” Luis Ríos, a paleoanthropologist at the National Museum of Natural History of Spain, said Wednesday.

Between 2000 and 2013, excavators removed more than 2,500 fossilized bones from the Spanish cave system known as El Sidron. Researchers have so far identified 13 individuals. This includes several adults, as well as the young boy and a child of about 2 or 3 years old. The bones were jumbled and must be pieced together, jigsawlike. Some of the bones have cut marks made after death, suggesting postmortem cannibalism.

The sophistication of the stone tools found in El Sidron indicate these archaic humans lived during the Middle Paleolithic period, about 49,000 years ago.

About 36 percent of the juvenile Neanderthal’s skeleton was still intact. El Sidron J1, which is what the researchers called him, had a complete lower jaw, 30 teeth, bits of skull, backbone, ribs, arms and a knee. He would have been about 3-foot-8 and 60 pounds. Though tests of his ancient DNA were inconclusive, the teeth size and bone shape indicated the Neanderthal was male.