Skelatal studies indicate that humans crossed the Pacific and colonized South America before anyone lived in North America (Dixon, 2000). The earliest skulls lack the Mogoloid traits of people from Siberia. Intead, South American skulls are similar to Polynesians and Australians. Colonization of North America probably began in South America, spreading south to north across the Great Plains (Hofman, 2000). Regional diversity shown in South America occurred at the time the Clovis spread in North America, around 11,000 ya (Gruhn, 2000). Regional technological traditions, and adaptations to different environments in South America were diferent from the Clovis culture. This supports Pre-Clovis existence, and supports a human presence in South America at the same time as the Clovis arrival in North America. The sites excavated, such as Monte Verde in south-central Chile and and Lapa do Boquete in the interior uplands of eastern Brazil that support the Pre-Clovis theory, were subject to recent controversy. Some of the dates in question suggest occupation of South America occurred around 35,000 ya. A list of links concerning this controversy is available in the reference section.

Statistical analysis on a few available early American skulls looked at variations in cranio-facial features between early (10,000-9,000 ya) and more recent Native Americans have implicated the first colonizers to be from the Jomon of Japan or other populations from southern or central Asia (Steele, 2000).