Nearly 5,000 cave paintings were discovered in northeastern Mexico in 2006 . This year , archeologists revealed their initial findings . The ages of the paintings are still not known . But they are believed to have been made by hunter - gathering groups .
Nearly 5,000 cave painting were discovered in northeastern Mexico in 2006 . This week , archeologists revealed their initial findings . The ages of the paintings are still not known . But they are believed to have been made by hunter-gatherer tribes .