* Saqqaq and Dorest Paleo-Eskimo populations are traceable to a wave of migration ca. 3500 BCE. These two archaeological cultures represent a single wave of demic migration and have genetic identity with each other (but admixed very little with other Native Americans before their demise).
* Early Na-Dene people arrive in Alaska ca. 1500 BCE.
* The 6th to 7th century CE Berginian Birnirk culture (in turn derived from Siberian populations) is the source of the proto-Inuit Thule people, who were the last substantial and sustained wave of pre-Columbian peoples to migrate to the Americas.
There were also several instances of less substantial and sustained migration, many of which have just become widely known:
* Around 1000 CE, Lief Erickson led a small population of Vikings to a short lived agricultural settlement called Vinland in maritime Canada. Recent discoveries announced in National Geographic in November of 2012 established that there were trade relations between the Vikings and indigeneous Arctic people at around the same time at the Northern tip of Canada's Baffin Island.
* From around 900 CE to 1100 CE, the "people who lived . . . in what today is the Lambayeque region, about 800 kilometers (500 miles) north of Lima, [Peru] had genetic links to the contemporaneous populations of Ecuador, Colombia, Siberia, Taiwan and to the Ainu people of northern Japan." These people were practitioners of the Middle Sican culture. It is not clear to what extent this contact was Austronesian in origin.
* I said then that:
Late in the period of Austronesian expansion (probably not earlier than 700 CE, with radiocarbon dated examples found in the Cook Islands by 1000 CE), perhaps from a final launching point at Easter Island, the kumara, a yam-like plant native to South America and possibly native to Peru, entered Austronesian territory and became a staple food. But, no genetic traces of the New World are found in Austronesian populations. It is possible that the kumara's arrival in Oceania and the Asian genetic influences found in Middle Sican graves involved the same instance of cultural Old World-New World contact.The evidence now contradicts that contention insofar as it claims that there is no genetic evidence of Precolumbian contact in Polynesia. Razib Khan notes a new paper demonstrating that Easter Islanders have approximately 8% Native American admixture in their autosomal DNA arising from a Precolumbian admixture event. He notes that: "The rough dates for Amerindian ancestry admixture are in the range of 1300 to 1400 A.D., which match reasonably well with when Easter Island was settled."
* Razib also notes in the same post a new paper whose abstract states:
[W]e present 14C dates, and morphological, isotopic and genomic sequence data from two human skulls from the state of Minas Gerais, Brazil, part of one of the indigenous groups known as ‘Botocudos’. We find that their genomic ancestry is Polynesian, with no detectable Native American component. Radiocarbon analysis of the skulls shows that the individuals had died prior to the beginning of the 19th century. Our findings could either represent genomic evidence of Polynesians reaching South America during their Pacific expansion, or European-mediated transport.As Razib sums up the finding of the paper in that post:
[H]eretofore the reasonable assumption about these Polynesian remains in interior Brazil were the product of escaped slaves, but there is an 80-90% probability that they died before any such enslavement of Polynesians could have occurred. In fact both remains may be pre-Columbian!Both of the new papers appear in the most recent issue of the Journal Current Biology.
* Wikipedia summarizes many, but not all of these contacts, and adds others that I have not listed above. Few are credible, but there is plausible evidence to support a few additional minor Old World-New World contacts.
* The Austronesians, the culture behind both of the latest two finds, are the same seafaring people who transplanted a community of their people from Indonesia, language intact, all of the way to Madagascar, with a small amount of South Asian admixture picked up along the way.
Of course, while these contacts did occur, none of them had the epic consequences that the era of European contact with the Americas begun by expedition of Christopher Columbus did.