How do anthropologists say the Oimecs came to be in Mexico?

The Olmec had their origins in the Tabasco region and then moved to Mexico

Explanation:

The Olmec were the earliest civilization found to be in the American region and they developed in southern Mexico in the swampy lowlands of the Bay of Mexico area.

Before this they seem to have originated with the Tabasco regions and their farmlands.

The movement to south Mexico came to be because of the conducive environment and the presence of alluvial soil in the region which facilitated the development of a larger population.