<P> According to the most generally accepted theory of the settlement of the Americas, migrations of humans from Eurasia to the Americas took place via Beringia, a land bridge which connected the two continents across what is now the Bering Strait . The number and composition of the migrations is still being debated . Falling sea levels associated with an intensive period of Quaternary glaciation created the Bering land bridge that joined Siberia to Alaska about 60--25,000 years ago . The latest this migration could have taken place is 12,000 years ago; the earliest remains undetermined . </P> <P> Three major migrations occurred, as traced by linguistic and genetic data; the early Paleoamericans soon spread throughout the Americas, diversifying into many hundreds of culturally distinct nations and tribes . By 8000 BCE the North American climate was very similar to today's . A study published in 2012 gives genetic backing to the 1986 theory put forward by linguist Joseph Greenberg that the Americas must have been populated in three waves, based on language differences . </P> <P> Native American cultures are not included in characterizations of advanced stone age cultures as "Neolithic," which is a category that more often includes only the cultures in Eurasia, Africa, and other regions . The archaeological periods used are the classifications of archaeological periods and cultures established in Gordon Willey and Philip Phillips' 1958 book Method and Theory in American Archaeology . They divided the archaeological record in the Americas into five phases; see Archaeology of the Americas . </P> <P> The Clovis culture, a megafauna hunting culture, is primarily identified by use of fluted spear points . Artifacts from this culture were first excavated in 1932 near Clovis, New Mexico . The Clovis culture ranged over much of North America and also appeared in South America . The culture is identified by the distinctive Clovis point, a flaked flint spear - point with a notched flute, by which it was insecarbon - dating methods produced results of 11,050 and 10,800 radiocarbon years BP (roughly 9100 to 8850 BCE). </P>

How did the erie canal impact american history and peoples lives