"Reproduction with related individuals creates more genetic abnormalities," said Eli Coleman, a professor and academic chair in sexual health at the University of Minnesota Medical School. "It seems the incest taboo has its evolutionary advantages. Social structures are set up within cultures, which preserve what has probably been known for centuries and discourage interfamilial relationships."
"Here is a case that the sociopsychological aspects of the incest taboo probably has at least part of its roots in a biological imperative -- that of probable genetic mutation," said sexuality expert David Greenfield, clinical director of The Healing Center, LLC in West Hartford, Conn.
But the incest taboo, at least in the recent case in Australia, isn't ironclad -- a fact that became readily apparent when the couple appeared on Australia's Nine television network's "60 Minutes" program to explain their unusual relationship.
Part of the reason for this, Turner says, could be linked to the fact that Deaves left the family home when his daughter was only an infant and that he did not see her for the next 30 years. Any Westermarck-like effect that could have existed between the father and daughter would therefore not have had the opportunity to develop.
Turner adds that compared to mother-son and brother-sister incest, father-daughter incest is actually more common.
But despite this fact, it does not mean that children of father-daughter incest are less likely than other children of incest to have genetic problems. Indeed, while the Deaves' new daughter is reportedly healthy, court documents reveal that the couple had another child in 2001 who died of congenital heart problems.
"It is very likely that this malformation was due to incest because they share 50 percent of their genes," Turner said.