Despite the many things that I do not agree with the church on, in my opinion the church(and not biology) has it right on sex! Sex is not just sex for two major reasons:
1) Sex is the most intimate thing you can do with another human being.
2) Sex results in new human beings, whose lives should be considered before the act of sex takes place.
What are my values with respect to sex? Well I think virginity is a good thing. I respect people who keep their virginity until they meet someone who they want to build a life and have children with, however I think it is unhealthy to focus on your virginity or to think of yourself as having lost a part of yourself when your virginity is lost. Non virgins should be valued pretty much as equally as virgins in the world of sex and relationships. Ideally I think that people should discuss how committed they are before having sex and they should be committed so that if a child was to be the result of sex, that child would have the highest possible chance of having his or her needs met. That child would have the benefit of two committed parents.
I know that the reality is very different from the ideal and that is okay, but we should not change the ideal just because most people are unable to achieve it though. It is an ideal; we can explain to people that being able to achieve this ideal is unlikely and that there is no reason to beat yourself up over it; yet still this is the ideal because it is what is most likely to give the best results. I think that we should look at sex as intimate and something that should ideally only be done within the context of stable relationships, however if we do have sex with the wrong person that should be shame-free. We should not be encouraged to stay in sexual relationships with people who we would not have kids with, but we should also not feel guilty about having sex with the wrong person or about giving in to our very natural desires to have sex simply for pleasure.
I am weird like this but personally speaking if my husband was to cheat on me as hurt as I would be I would not leave him (unless it was with a close friend or relative). As long as he can explain it to me I would be okay with and move on, we all make mistakes and we all give into our desires even though we intend not to. I can also see myself potentially being okay with an open relationship if there was a way for me to be 999% sure that my husband would not be getting other women pregnant and that I would not get any STDs; this is not reality though. In reality (no matter WHAT, ie even with condoms/a vasectomy) I would fear him either giving me an STD or getting someone else pregnant. Plus I used to be an easily jealous person.
So giving into sexual desires, if you genuinely have those desires, is not bad; but it is also not the ideal! According to biology it is the ideal because biology just wants as many fit children as it can get and fit to biology is unfortunately still physical might and having a skill set more needed in the hunter-gatherer days than what is needed today. So on this one point Religion rather than biology is my religion because mankind has already created an unnaturally large society that biology did not get time to cater for and so we cannot just depend on our biological instincts when it comes to sex. Depending on biology here would mean promoting a structure for society that no longer works. Yes there are health benefits that come from giving into sexual desires, but at the same time I feel it is important for society to understand that sex is not just sex and that it is not really in the best interest of society as a whole to encourage people to give into to their desires without preparing for the children that may result.
It is also not in the best interest of society to demonize causal sex, but we as a society need to keep in mind that since sex results in babies, and babies/children do better within family settings. Who we are having sex with and the type of relationship we have when engaging in sex therefore DOES matter. Of course birth control has changed a lot with respect to this argument and with birth control sex can potentially be just sex, but birth control is not 100% effective, and in my opinion being really safe means preparing for all possible outcomes no matter how unlikely.