If there was no religion, and money didn't make greedy good looking people get with ugly decrepid people, then life is only one thing:
HOW MANY BABIES YOU CAN PRODUCE TO CARRY ON YOUR GENES.
That's it. That is why instinctively, religious or not, all heteroesexual men want to have sex with women who can carry on their genes to children that are healthy and have a better chance of surviving, ie women that look in shape and are pretty.