Hmm. In a DNA paternity test, they are looking for gene sequences that are copied 'verbatim' from the person who is suspected of being the biological father. It gets less accurate with each generation removed from the child; so it's less accurate for determining grandparents and still less accurate for determining great-grandparents, and so on. It would be useless for establishing 'paternity' over thousands of generations.
I'm not anti-Christian. I'm anti-stupid.