Per http://en.wikipedia.org/wiki/Chicken#South_America
Can someone parse this section for me? Particularly the first sentence of the last paragraph of the section (the quoted bit). I don't know what "clustering" is exactly, and the clauses of the first sentence sound contradictory to me if I can try to understand them at all.
Why did they decide the chickens weren't pre-Columbian and/or weren't domesticated gallus gallus?
It might be advantageous to read a source that wasn't summarized in that way on Wikipedia. Try reading this instead or the actual journal publication if you have access.
Basically the study concluded that the chicken bones were more genetically similar to Eurasian breeds than Polynesian breeds.