Humans lived on Spanish plateau during Earth's last cold snap

Excavations at a rock shelter have revealed that humans lived in high and remote regions of what is now Spain during the coldest part of the last glacial period, between 21,400 and 15,100 years ago.

High-altitude regions are colder and more challenging than low-lying zones, but even so, the Spanish plateau probably “hosted a relatively dense human settlement”, says Manuel Alcaraz-Castaño at the University of Alcalá in Spain.

Beginning 2.58 million years ago, Earth has been through alternating periods of cold “glacials”, in which the area covered by ice and snow expands, and warmer “interglacials” where the ice retreats. The last glacial period occurred from about 115,000 to 11,700 years ago. It was at its coldest between 26,500 and 19,000 years ago, a time called the last glacial maximum. This posed a significant challenge for modern humans, who had arrived in Europe about 20,000 years earlier.

Conditions were particularly challenging on the meseta, a high-altitude plateau in what is now central Spain. Climate modelling by Ariane Burke at the University of Montréal in Canada and her colleagues concluded that as well as being cold and dry, the meseta was also highly unpredictable – making it harder to permanently settle there.

Nevertheless, people persisted. Since 2020, Alcaraz-Castaño and his colleagues have excavated a site called Charco Verde II in the Piedra river valley, Spain. Located around 1000 metres above sea level, Charco Verde II is a flat platform under an escarpment. Buried in the sediments, the team found fragments of charcoal from fires, animal bones with cut marks and signs of having been heated, and stone tools including blades and scrapers.

Radiocarbon dating suggests Charco Verde II was first inhabited between 21,400 and 20,800 years ago, and the residence ended between 16,600 and 15,100 years ago. It isn’t clear how continuous this was. “Occupations at the site were recurrent during 5000 years, but we still don’t know if there were prolonged periods where the site was not inhabited,” says Alcaraz-Castaño.

Preserved pollen and animal bones suggest the area was dominated by open grasslands, dotted with trees, such as juniper, and populated by herbivores like horses and ibex. Average annual temperatures were about 6 °C lower than today, says Alcaraz-Castaño, so in winter “ice and snow were probably everywhere around the site”. However, the summers were probably fairly mild.

“It’s nice to see people pushing the boundaries and finding new sites,” says Burke, who wasn’t involved in the new study. “In the early Upper Palaeolithic, people were perfectly capable of adapting to very cold environments.”

Her modelling studies identified the Charco Verde II region as relatively suitable for settlement because its climate was less variable than the central meseta. “It makes sense that the sites are where they say they are,” she says.

Burke adds that it is possible people did live even in the very harshest parts of the meseta, but such settlements may have been both scarce and short-lived. “Our chances of finding sites [there] are fairly small,” she says.

Such settlements were made possible by a host of behavioural skills. “Both fire and clothing were regular technologies of Upper Palaeolithic hunter-gatherers, as were some sorts of dwellings,” says Alcaraz-Castaño.

So far, Charco Verde II hasn’t yielded direct evidence of clothing. However, Burke notes that the team did find stone tools called burins that were often used to create the eyes in needles – “which means fine sewing skills and tight seams, so waterproof and windproof clothing”, she says.

Social networks were probably just as essential for survival, says Burke. Such networks “provide people with the means to exchange information over quite large territories”, she says, and to take shelter when conditions are harsh.

In line with this, the Charco Verde II dig revealed four perforated shell beads, one of them with traces of an ochre pigment. Such jewellery often served as a marker of identity, says Burke, and is a hint that, even in a sparsely populated region, people were still maintaining social relationships with other groups.