I have read Jared Diamond,s book and found it very interesting but not always convincing. I did read, many years ago, a book by Elaine Dewar called "Bones, Discovering The First Americans". She talked a lot about the sites in the Southern Hemisphere and asked the same question that also occurred to me. Thanks for your reply, I will now go back and have another look at both authors.
Very interesting and informative thread, thanks.