elderwho, vicarious baptism was around long before the thief died on the cross; but, yes, he died before I had a chance to make the inference.
As for DNA, here's the story. Lehi with his family, (about 25 people) came to the Americas and found entire civilizations of people here. They intermarried with them and with each other. His religion and his culture is what survived, but how much of his DNA do you think is going to make it through 2,000 years of procreation? See how this DNA claim is a straw man?