In the latter part of the 19th century, the Marquis of Nadaillac commented on what he thought were clear similarities between the shell mound cultures of the Americas and those of Neolithic Europe.
"I cannot close this account of the kitchen-middings, without
calling attention to two very interesting facts. The importance of
these mounds bears witness alike to the number of the inhabitants who dwelt near them, and the long duration of their sojourn. Worsaae sets back the initial date of the most ancient of the shell-mounds of the New World more than three thousand years. This is however a delicate question, on which in the present state of our knowledge it is difficult to hazard a serious opinion. It is easier to come to a conclusion on other points: the close resemblance, for instance, between the kitchen-middings of America and those of Europe. In both continents we find the early inhabitants fed almost entirely on fish; their weapons, tools, and pottery were almost identical in character; and in both cases the characteristic animals of Quaternary times had disappeared, and the use of metals still remained unknown. Are these remarkable coincidences the result of chance, or must we not rather suppose that people of the same origin occupied at the same epoch both sides of the Atlantic?"
It has been rather popular to theorize on pre-Columbian passages from Europe to the Americas. More recently, we have seen the theory that the Paleo-Indian Clovis culture originated in Europe. However, rarely do we hear of the possibility of pre-Columbian journeys from the Americas to Europe.
I would say that these definitely occured and Austronesians played a part in these journeys.
Shell mounds from late Mesolithic Maglemose culture, Denmark
Maglemose cultural artifacts including bifid canoe and fish hooks
On left and right, renderings of boat-shaped burials from Slätteröd, Sweden and Batan Island, Philippines (from Chris Ballard et al.), a Maglemose boat-shaped burial in center (http://cientual.com/7tesis/Paginas/C12/Ritos.htm)
The use of boat burial or boat-shaped burials were common in both Scandinavia and Southeast Asia. The Niah caves have examples of very early boat burials and also cave art showing what are apparently bifid boats. These are Neolithic burials and the artwork is positioned over the high water mark of the last major sea flood.
Another common cultural feature is found in the types of bailers used in both regions to empty water from boats. Pedersen has noted a similarity between the Proto-Oceanic and Danish words for this device:
*asu "scoop or ladle out; ladle, bailer," Proto-Oceanic
øse "bailer, scoop," Danish
The "Oceanic" bailer from Hornell. Similar bailers are also found in Pacific coast Amerindian culture
We will study next the linguistic evidence that links the Nusantao with these far-ranging similarities.
Paul Kekai Manansala
Ballard C.; Bradley R.; Myhre L.N.; Wilson M. "The ship as symbol in the prehistory of Scandinavia and Southeast Asia," World Archaeology, December 2003 2004, vol. 35, no. 3, pp. 385-403(19).
Hornell, James. Water Transport: Origins and Early Evolution (1946, repr. 1970).