As with most major governmental projects, archaeologists surveyed the Proyecto Hidroeléctrico Reventazón are and located 66 settlement sites.
The Instituto Costarricense De Electricidad said Wednesday that some of the oldest material was dated 12,2000 years ago. The radiocarbon tests were done on vegetable matter that appeared to have ben manipulated by humans, said Luis Hurtado de Mendoza, archaeological coordinator for the project.
He said that this was the earliest evidence of humans in Central America.
The Reventazón project area is 1,018 hectares, a bit more than 2,500 acres. The location is in Siquirres.
The archaeologists also found many types of stone tools, Petroglyphs and grave sites on both sides of the Río Reventazón. They are being turned over to the Museo Nacional.
Some 12,200 years ago the world was emerging from the last ice age. Megafauna roamed Costa Rica, including giant sloth, Mastodon and giant armadillos
Although 12,200 years is old by Costa Rican standards, some sites in SouthAmerica go back 40,000 years, although such ages are controversial in academic circles.