Anti-incest

The mistake on the part of the anti-incest taboo protagonists is not their insistence that we recognize the conventional features of our social arrangements […]

Of course, most systems have some failure rate — incest does occur, because innate behaviors direct rather than dictate (chimps also have an occasional anti-incest failure).

Even when we're at our most arbitrary and forgetful of our own stance, we remain antibestiality and anti-incest.