Pope Benedict XVI on Friday weighed in on a heated debate over gay marriage, criticising new concepts of the traditional family and warning that in the fight for the family, mankind itself is at stake.
"In the fight for the family, the very notion of being - of what being human really means - is being called into question," Benedict said in Italian during an end of year speech.
"The question of the family... is the question of what it means to be a man, and what it is necessary to do to be true men," he said.
The pope spoke of the "falseness" of gender theories and cited at length France's chief Rabbi Gilles Bernheim, who has spoken out against gay marriage.
"Bernheim, has shown in a very detailed and profoundly moving study that the attack we are currently experiencing on the true structure of the family, made up of father, mother, and child, goes much deeper," he said.
He cited feminist gender theorist Simone de Beauvoir's view to the effect that one is not born a woman, but one becomes so - that sex was no longer an element of nature but a social role people chose for themselves.
"The profound falsehood of this theory and of the anthropological revolution contained within it is obvious," he said.
On Monday, the Vatican's newspaper described laws on gay marriage as an attempt at a communist-like "utopia", a day after tens of thousands of demonstrators turned out in France to support legalise both marriages and adoption for gay couples.