Teams of up to 70 people are working on the digs at the Lozoya River Valley.

The Lozoya River Valley, in the Madrid mountain range of Guadarrama, could easily be called "Neanderthal Valley," says the paleontologist Juan Luis Arsuaga.

"It is protected by two strings of mountains, it is rich in fauna, it is a privileged spot from an environmental viewpoint, and it is ideal for the Neanderthal, given that it provided the with good hunting grounds."

This is not just a hypothesis: scientists working on site in Pinilla del Valle, near the reservoir, have already found nine Neanderthal teeth, remains of bonfires and thousands of animal fossils, including some from enormous aurochs (the ancestor of cattle, each the length of two bulls), rhinoceros and fallow deer.

The Neanderthal is a human species that is well known and unknown at the same time. It is well known because numerous vestiges have been found from the time when they lived in Europe, between 200,000 and 30,000 years ago. But it is also unknown because of the many unresolved issues that keep cropping up, including, first and foremost: why did they become extinct just as our current species made an appearance on the continent?

Nobody knows for sure whether the Neanderthal was able to talk, or whether they shared territory with Homo sapiens, or whether both species ignored each other until one - ours - proliferated while the other got lost forever... Scientists in charge of the sites at Pinilla del Valle could make significant contributions to finding the answers to these and other questions about the lives of the Neanderthal people.

"There are around 15 sites in Spain: in the Cantabrian mountain range, along the eastern Mediterranean coast and in Andalusia, but none on the plateau, where there are no limestone formations and no adequate caves to preserve human remains for thousands of years," adds Arsuaga. But Pinilla del Valle is an exception to the rule. "There is limestone here. It was like a cap made of stone under which the Neanderthal presumably took refuge to prepare for the hunt, to craft their tools, to eat... It's not that they lived inside in the sense of a home; they wandered in the fields, and this was probably more like a base camp to take refuge when they needed to."

It is clear that the Neanderthals took care of their dead in some way

"The site, which has great potential, extends some 150 meters and we are now working in three areas: the cave of Camino, the refuge of Navalmaillo and the cave of Des-Cubierta, which cover three different time frames," says Enrique Baquedano, director of the Regional Archeology Museum in Madrid.

It was on the floor of Des-Cubierta that the Neanderthal must have placed the dead body of a small child aged two-and-a-half to three years old. They placed two slabs of stone and an aurochs horn on top, and set the body on fire. Baquedano explains that they found some of the child's teeth - they call it a little girl, although they have no scientific evidence of its gender - as well as a piece of coal that turned up just a few days ago and which will enable precise dating. "Complete burials, with a clear structure that allows [researchers] to reconstruct behaviors, is a very rare thing in any part of the world," says Arsuaga, who is also co-director of the excavations at the major prehistoric site of Atapuerca.

Standing next to him, Baquedano points at the spot where they found the coal from that bonfire, perhaps a ritual of some sort, and which will be subjected to carbon 14-dating techniques.

"We are convinced that it was an intentional deposition of the girl's body; perhaps there were more burials at Neanderthal sites but they were not recognized as such," says the museum director.

The fact is, the Neanderthal took care of their dead in some way. Traces of them have also been found in France and Israel.

Here at the Madrid valley, archeologists and paleontologists get busier as the days go by. A total of 70 people scattered over three sites dig among the sediment with chisels and brushes; they clear through the rock with jackhammers, they wash kilograms of extracted earth so that not even the smallest noteworthy piece will go by unnoticed, and every excavated centimeter is documented. This scientific work has been going on every summer for a decade, "for 40 days, in two shifts," explains César Laplana of the regional museum.

The nine Neanderthal teeth discovered so far are between 60,000 and 90,000 years old, and several of them appeared in what must have been hyena dens, where the animals probably devoured and destroyed the bodies. "Teeth are the most resistant of all organic tissue; they keep better than the rest of the skeleton, and they provide lots of information about the diet, the diseases, and the passage from childhood to adulthood," continues Laplana.

"The Neanderthal lived both in the interglacial and the glacial periods," explains Arsuaga. After an ice age that made half of Europe look like Greenland does today, the interglacial period began around 130,000 years ago with a climate that was actually warmer than today's; then, 85,000 years ago the last ice age began, ending 11,500 years ago. The excavations at Pinilla corresponding to the interglacial period produced many remains of fallow deer (a Mediterranean species), tortoises, porcupines and brown bears, as opposed to the cave bears of the glacial period.

Over at the cave of Des-Cubierta, Javier Somoza, a student at Salamanca University, walks up to Baquedano and shows him an artifact wrapped in white paper: it is a tool that he has just found in the ground. "Yes, I was very excited," says Somoza about the bit of pink quartz.

Thousands of stone tools have already been found. "The best stone for sculpting is flint, but there's none in this area, so they had to make do with what they had handy. So they adapted their technique to quartz. "It's worse, but it works and it represents an admirable technological adaptation."

And what about hunting? "They used wooden lances with fire-hardened tips."

"Here, in this valley so full of rich sites, we can find out lots of things about the Neanderthal, their lives and their deaths, their climate, their technology and their economy," concludes the archeologist. "It's just a matter of time."