Scientists of several nationalities have estimated paintings found in three caves in northern Spain to be between 30,000 and 40,800 years, which would make them the oldest ever discovered in Europe.

The discovery, made using a dating method known as uranium-thorium, will be published Friday by Science magazine.

The study was carried out at 11 caves featuring outstanding examples of pre-historic art, but the most significant results were obtained from Altamira, El Castillo and Tito Bustillo.

In the Altamira cave, located in the northern Spanish autonomous community of Cantabria, a painting of a red horse was found to be more than 22,000 years old and a large, red sinuous triangular sign was determined to date back more than 35,600 years.

In El Castillo, the experts identified an indeterminate black animal drawn at least 22,600 years ago; one red sphere between 34,100 and 36,000 years old; handprints that date back 37,300 years and a second red sphere at least 40,800 years old.

An anthropomorphous figure between 29,600 and 35,500 years old was found in the Tito Bustillo cave.

According to the study, cave paintings were a widespread form of artistic expression among human groups between 35,000 and 40,000 years ago.

The results also raise the possibility that Neanderthals could have been the artists of the oldest paintings and that therefore the capacity to create was not the exclusive domain of homo sapiens.

Among those positing that theory is the University of Barcelona's Joao Zilhao, who said such a finding would not be surprising considering what scientists have learned about Neanderthals over the past 10 years.

The investigation began in 2005, when the results of studies on cave paintings in France and Portugal dating back at least 20,000 to 25,000 years began to be published.

The results presented Thursday pertain only to the first phase of a study that is ongoing and will likely result in new discoveries.