There is growing evidence that people reached a land bridge connecting northeastern Asia to what is now Alaska around 23,000 years ago, arriving in the Americas perhaps 18,000 to 16,000 years ago, and exploring and settling many parts of the continents by 15,000 to 14,000 years ago.
     A team led by geo-archaeologists Jessi Halligan of Florida State University and Michael Waters of Texas A&M University reports that a group of hunter-gatherers either butchered a mastodon or scavenged its carcass on Florida's Gulf Coast about 14,550 years ago. Stone tools discovered in an underwater sinkhole in the Aucilla River show that people were present at the once-dry Page-Ladson site at least 1,000 years before Clovis people appeared in North America around 13,000 years ago.
     Radiocarbon dating of twigs, seeds and plant fragments from submerged sediment layers provides a solid age estimate for six stone artefacts excavated by scuba divers. Excavations from 2012 to 2014 also uncovered animal bones, revealing that Florida's ancient hunter-gatherers lived alongside mastodons, bison, and other large creatures for about 2,000 years before the animals died out about 12,600 years ago.
     Investigations from 1983 to 1997 yielded eight stone artefacts and a mastodon tusk displaying parallel grooves possibly made by people using stone tools. An initial radiocarbon date of about 14,400 years for these finds, as well as a proposal that people had butchered the mastodon, drew challenges from several researchers. A reexamination of grooves on the mastodon tusk conducted by palaeontologist and study coauthor Daniel Fisher of the University of Michigan concludes that tool users probably made the marks while removing the tusk from the animal's skull. Fisher suspects Page-Ladson people sought edible tissue at the tusk's base and in its inner cavity, as well as ivory for weapons.

Edited from ScienceNews (13 May 2016)