A question that has been plaguing man since time immemorial.
"Cultural values about male beauty were completely different back then. Today, big penises are seen as valuable and manly, but back then, most evidence points to the fact that small penises were considered better than big ones. Large penises were associated with very specific characteristics: foolishness, lust and ugliness."
Check out the companion piece, "A Brief History of Hairless Vaginas in Art (NSFW)"