The Olmecs were an ancient civilization from Earth.
Commander Chakotay owned an Olmec figurine, which ended up with him after he was stranded in the Delta Quadrant. In 2375, Kurros requested this figurine as payment to rescue the USS Voyager from the Hazari. (VOY: "Think Tank")
According to the Star Trek Encyclopedia, 4th ed., vol. 2, p. 103, the Olmec civilization flourished in Mexico from ca. 1500 BCE to about 400 BCE.
It is unclear whether Chakotay's Olmec figurine was a reproduction or an authentic artifact he somehow retrieved from the Val Jean before its destruction.