Further evidence points to footprints in New Mexico being the oldest sign of humans in Americas

New research shows that fossil footprints discovered at the edge of an ancient lakebed in New Mexico's White Sands National Park date back to between 21,000 and 23,000 years ago. Previously, archaeologists thought human ancestors arrived about 15,000 years ago. The research was published Thursday in the journal Science. Scientists analyzed conifer pollen and quartz grains found at the site to reach date estimates. Earlier research that analyzed seeds of aquatic plants found at the site also produced similar date estimates. Ancient humans at White Sands lived alongside giant ground sloths, bison and other megafauna.