What can we learn from studying animal DNA? Do studies of animal and human DNA produce similar pictures of the peopling of the pacific?
I guess what's the most interesting about looking at all the different animal DNA or the animal models for the human settlement is that they're not necessarily telling us exactly the same thing, and that tells us something about human choice and decision-making and processes. But I guess in terms of overall patterns and what we can say they're telling us is that things were much more complex than we perhaps previously thought. There are some models out there that people may have heard of or are familiar with in terms of Pacific settlement—things like the "Fast Train" model—which are really simplifications and not necessarily real models that people have put out for testing. But the idea that perhaps Pacific peoples came with an entire suite of organisms from the very beginning and they kept those, you know, animals—that suite of animals—kind of in a little hermetically sealed pod or something as they moved out into the Pacific, we're certainly seeing that that's not the case, and the genetic data is indeed suggesting that we do have multiple introductions and multiple lineages of dogs and pigs and chickens and rats. And so that's telling us that really it is a much more complex and probably fluid system of people coming into the Pacific and interacting and, you know, possible multiple groups of peoples coming into the Pacific carrying their own lineages or their own kind of populations of these animals. Rather than counting numbers of those, we see that it is probably a complex, ongoing process over thousands of years. That's kind of exciting and much more—if you think about modern migrations and things, people tend to take advantage of situations and follow in others' footsteps and so forth, and it's a much more kind of dynamic system.
You and your colleagues recently studied a chicken bone archaeologists uncovered in Chile at a site that predates the arrival of Europeans in South America. Did Polynesians bring this chicken to Chile?
Certainly the animal genetics have recently contributed to our understanding of interactions of, you know, Pacific islanders reaching the Americas, in the sense that we found Polynesian chicken bones or chicken bones that we've traced to Polynesia in the Americas. And some of, you know, I guess we said that this is the first hard evidence, that really—I mean, we knew, most Pacific prehistorians certainly accepted that there had to have been contact between Polynesians and South Americans prior to the arrivals of the Europeans in the Pacific, because when the Europeans arrived, Polynesian peoples and Pacific peoples had plants that are clearly of South American origin, in particular the sweet potato and the bottle gourd.
Most Pacific prehistorians would accept that Polynesian sailing technology and the demonstrated abilities of Pacific peoples to sail across the Pacific Ocean made it much more likely that Polynesians were the ones who made that contact. You know, why would Polynesians have stopped moving across the Pacific when they reached the last of the islands? When they get to Easter Island, for example, they didn't have a map saying, or a sign saying, you know, last island in the Pacific before you hit a continent. They would have kept going. But we had no actual, tangible evidence of something of Polynesian origin arriving in the Americas until our colleagues in Chile found these chicken bones, and chickens are not native to the Americas. They were not present in the Americas at any point in the distant past, and it was believed that the Europeans had probably brought them—the Spanish and Portuguese, and, you know, from Columbus onwards they were carrying animals across from Europe to the Americas. So when our colleagues found these bones in a site that they believed to be pre-Columbian, they were very excited and thought that they might be Polynesian, and so we agreed to do the DNA analysis on them.
If chickens made it to Chile, what other animals might Polynesians have introduced to the New World before the arrival of Europeans?
So were chickens the only animals that Polynesians introduced? We don't know. And I'm actually heading over to Chile in December to work with my colleagues there to look through some more midden bones—bones that are dug up along the coast and particularly on the offshore islands in the area of Chile where they found the chicken bones to see whether other animals might have made it.
What animals might have made it is going to depend on what animals were in the source islands. So if those canoes had gone from Easter Island, for example, only the chicken and the rat were on Easter Island prehistorically, so those canoes couldn't carry pigs or dogs. If they were coming from Hawaii or from the Marquesas islands, depending on whether we're talking about contact with North America or South America, they could have been carrying the other animals. Would those introductions have survived if they were carrying, you know—I think probably it's likely that they were carrying rats, but there are already numerous rodents in the Americas, particularly on the mainland. But there might not have been rodents on some of these offshore islands, so the introduction of Rattus exulans might have been successful on the offshore islands where it might not have been successful on the mainland. So that's why we're going through and looking at these midden collections to see if we can find any rat bones. Native Americans had dogs—for thousands of years they had dogs before people were in Remote Oceania. So we could possibly look for evidence of Polynesian dog DNA lineages in some American dogs, but again, our chances of finding that are pretty small. It would just be the introduction of a few individuals, and would they have a major impact on a dog population that was already present? Probably not. Pigs, again, if Polynesians were carrying pigs, would they be seen as something that was important that people would want to maintain? Biologically could they be maintained? You know, those are all questions we don't know. But I certainly wouldn't completely rule it out. But I think our best chances are of finding evidence of rats. They're easy to introduce and probably more likely to survive, particularly in the island environments, than the larger mammals.