How do some scientist explain the appearece of the sweet potato in both americans and islands of the pacific

It is most likely because of the sweet potato, which was among the potatoes native to the north. South America, was brought to the pacific by Spanish explorer after their discovery in the New World "America Today". However, the cultivation in some parts of Polynesia actually pre-dates European explorations by about 500 years, so the possibility exists that early Polynesians traveled as far west as central America and them transplanted the sweet potato's then.  The sweet potato is a botanically distinct from bother the African/Asian yam and the new Zealand yam.