Below are many artifacts from Chiapas Mexico. These Blacks predate the Olmec by 100s of years.

In Belize , around 2500 B.C., we see evidence of agriculture. The iconography of this period depicts Africoids. And at Izapa in 1358 B.C., astronomer-priests invented the first American calendar. In addition numerous sculptures of blacks dating to the 2nd millennium B.C, have been found at La Venta, Chiapas, Teotihuacan and Tlatilco.
Chiapas Blacks
The earliest culture founded by Blacks in the Pacific coats region was the Mokaya tradition. The Mokaya tradition was situated on the Pacific coast of Mexico in the Soconusco region. Sedentary village life began as early as 2000BC. By 1700-1500 BC we see many African communities in the Mazatan region. This is called the Barra phase or Ocos complex.
During the Barra phase these Blacks built villages amd made beautiful ceramic vessels often with three legs. They also made a large number of effigy vessels.
The figurines of the Ocos are the most significant evidence for Blacks living in the area during this period. The female figurine from Aquiles Serdan is clearly that of an African woman.

Ocos Female

The Blacks of the Mokaya traditions were not Olmec. The civilization of the Mokaya traditions began 700 years before the Olmec arrived in Mexico.
Cherla

In most history text the Ocos are presented as the original founders of Mayan civilization. As you can see from the art they do not look like native Americans they look negro like other Africans.