In Spanish, the world for jigsaw puzzle is “rompecabezas”—literally, a head breaker.
Researchers in Spain flipped that process, taking hundreds of pieces of ancient bone that were found in a cave north of Madrid near Burgos called the “Pit of the Bones” and reconstructing 17 skulls of early humanoids dating back 430,000 years.
Fossilized remains of ancient humans are usually found individually, but the Pit of the Bones, which was first discovered in 1983, includes the largest number ever recovered from a single site. There has been much debate ever since they were found, about the age of the fossils and the precise species of human they represent.
“They are early members of the Neanderthal lineage,” Juan Luis Arsuaga of Madrid’s Complutense University, the lead researcher for the study that’s being published in the journal Science, told Reuters on Thursday. “The specific [species] is still an open question.”
Neanderthals are the closest extinct species to ours, Homo sapiens, and they coexisted with humans as recently as 40,000 years ago. Neanderthal skulls have a few distinct features, including a large brain, prominent jaws and large teeth.
The reconstructed Spanish skulls show Neanderthal features in the face and teeth, but have a brain case that could only accommodate a small skull.
Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved in the research, told NPR about the finding’s significance, “If we understand how Neanderthals evolved and what has been going on, exactly, in the course of Neanderthal evolution, then we could say what is special with us, what is different.”
Along with the skulls, the skeletons of 28 different individuals were reconstructed, all from the same shaft in the Pit of the Bones cave.
“For the first time in history,” Arsuaga told Reuters, “We can study a fossil population, not isolated fossils.” Most of the remains belonged to young adults and teenagers, he added.
Another of the researchers, the Australian geochronologist Lee Arnold of the University of Adelaide, was involved in the new dating of the site. It was previously thought that the remains were as much as 600,000 years old.
Arnold told Reuters, “As a result of this study we are able to answer two of the most important questions that surround the [Pit of the Bones] fossil assemblage: Who were these people? And when were they living on the landscape?"