kelley, darling, methinks you are confusing sex with chastity - which is a patriarchal test of woman's worth as chattel, or more precisely, child-bearing property. From the patriarchal point of view, she could do "evrything else imaginable" and that was just fine (the more the better from a male point of view - I may add) - but the vaginal penetration was different because it jeopardized her male owner's err... husband's his property right to the child (or children) she bore. Children being income producing labour power these days, they were the property of men - so whoever impregnated the woman had the property right to the children. Nothing ambiguous about it - patriarchy enshrined in chirstianity, pure and simple (the myth of divine rape err... impregnation of virgin mary and all that dirty old man fantasy that permeates religion).
now that children lost its income producing status (they are actually income consuming) they also lost their value to men - and presto our wonderfully impartial courts award custody to mothers, for "child's benefit" of course. But the old test of chastity - meaning proof of not being penetrated - still lives its ritualistic life.
But let me reitearte time and again - it has nothing to do with sex, but with property rights and "family values" i.e. the worthiness of a woman as a wife (i.e. child-producing chattel).
smooches
wojtek