The cave art may depict fungi with hallucinogenic properties, which would make them the oldest evidence of their use in Europe, NewScientist.com reported Sunday.
The Selva Pascuala cave mural near the town of Villar del Humo has as its central feature a bull, but it is a row of 13 small mushroom-like objects that interests two researchers.
Brian Akers at Pasco-Hernando Community College in New Port Richey, Florida, and Gaston Guzman at the Ecological Institute of Xalapa in Mexico say they believe the objects are the fungi Psilocybe hispanica, a local species with hallucinogenic properties.
P. hispanica has a bell-shaped cap topped with a dome and lacks an annulus -- a ring around the stalk -- like the objects depicted in the mural, they say.
However, even at 6,000 years old the painting isn't the oldest thought to depict hallucinogenic mushrooms anywhere in the world. A mural in Algeria that may show the species Psilocybe mairei is 7,000 to 9,000 years old, NewScientist.com reported.