Turkish Quadriped Family Raises Questions

My first thought when reading this article about the quadriped family in Turkey was this:

What if all the archaelogical "finds" of quadriped humanoids, are just like this family--genetic mutants because of too much familial marriage. All of these children are mentally retarded due to their parents being close relatives. Is it possible that humans don't have a quadriped ancestory at all, but an ancestory who enjoyed conjugal relations with relations? We know that practice goes waaaaay back.