Virtually each month brings a new discovery challenging the antiquity of the earlier settlers as to much older or much less. But one thing's for sure, Native Americans were here long before the Chinese of 1423 may or may have not been here. But if one had to tag a race to Native Americans, I think anybody would pretty much have to narrow it down to Asian.
Yup. See the dental work done by Christy Turnes at Arizona State University.(some surprises)
There was a population explosion of Northern Chinese (compared to others) sometime in the BC, can't pin down a date though.