Hunter-gatherers in the region located the drawings in the caves of Sierra de San Carlos in northeastern Mexico.

In the mountains of Mexico's Tamaulipas state, researchers are still placing a date on the paintings "through chemical analysis or radiocarbon."

Martha Garcia Sanchez, an archaeologist, states that the natives were able to resist Spanish rule by sustaining themselves with "water, plants and animals" in the hill country.

Fellow archaeologist, Gustavo Ramirez comments, "We have not found any ancient objects linked to the context, and because the paintings are on ravine walls and in the rainy season the sediments are washed away, all we have is gravel."

Ramirez also mentions that the discovery were drawn by inhabitants of "one or more cultures."

The paintings contains humans, animals, stars. Other abstract images are being decoded for their meanings.

The 11 sites found by the Mexican National Institute of Anthropology and History contained paintings of white, black, red, and yellow colors.