Well, this is neat. It seems that a really ancient skull found in Mexico, called the Penon Woman, dated to about 12000 years ago, appears to be Australian in origin. That's Australian Aborigine. What's more, the finding seems to be based not only on skull morphology, but also on DNA analysis.

"US laws that require the handing over of ancient remains to native Americans on the assumption that they are their ancestors, have prevented scientific analysis of many finds."

I've been saying something like this for years. This is what I think happened. Sometime between 50000 and 12000 years ago, during the last Ice Age, people in or near Australia, who had had boat technology for at least that long, began to migrate up the coast of Asia, and around to the Americas. They probably settled along the coast, in isolated, relatively diffuse communities. Then, later, when the ancestors of what we think of as Native Americans came in from the Bering Land Bridge, the Elders were either exterminated or forcefully absorbed. Genocide, in other words. I think that is the real reason why many Native American groups so forcefully oppose the study of things like Kennewick Man.