I've hear anal hurts really bad.
It would make sense that, despite this shift, males would still have some residual interest in the butt as well.
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Interestingly, at least according to Jared Diamond, the most likely reason that men are attracted to breasts is that, as we began to walk upright, it became harder and harder to put the extra fat deposits on the butt, and so females shifted it to the chest, where it was even more visible on a biped.