I was reading a bit, and it seems that the standard theory is that the Polynesian migration began in Southern China, around the same time that these artifacts are dated to. So, we could very well be looking at the artwork of the people who would soon get pushed out of China by migrants from the north, and ended up colonizing all those pacific islands.
However, recent DNA analysis suggests the migrations may have started a couple millenia earlier, so who knows?
The Pacific Islanders are more closely related to the Denisovians than any other people on earth.
New Lapita Find Re-dates Known Fiji Settlers (Jomon/Ainu)
"Staring out from an ancient piece of pottery, the mysterious face of a bearded man has given scientists a unique glimpse of what the first settlers of Fiji may have looked like."
"Preliminary analysis shows that the eerie-looking face consists of a prominent raised nose, the left eye and what might be eyelashes, said Roselyn Kumar of the University of the South Pacific's Institute of Applied Sciences"