English: Proposed models explaining the peopling of the Americas. (A) The earliest people exploring the Americas used stemmed projectile points and traveled along the coast ~16 ka ago, moved inland, and reached the Debra L. Friedkin site by ~15.5 ka ago and South America by ~14.2 ka ago (blue arrows). (B) A triangular lanceolate projectile point form develops in situ from the earlier lanceolate stemmed form ~14 ka ago, with Clovis developing ~13 ka ago and spreading across most of the United States and northern Mexico (red arrows). (C) Alternatively, the origin of Clovis may be explained by a second migration that occurs with people using triangular lanceolate points traveling through the ice-free corridor and reaching the Friedkin site by ~14 ka ago. Clovis develops in situ ~13 ka ago and spreads across central and eastern North America (red arrows). Archaeological sites with ages are shown. Colored regions on the map show the general distribution of Clovis, with highest densities in the east (brown), moderate densities in the central United States (orange), and light densities in the west (yellow), overlapping with the Western Stemmed Tradition shown by the cross-hatch pattern.