Five Science Insights Into Relationships

With the approach of Valentine's Day, love gurus, relationship mavens and infidelity experts (is that the same as an infidelity researcher, or is it someone who cheats on their spouse without getting caught?) take to the airwaves to tell you how to evaluate your relationship and determine the faithfulness of your partner.

While human relationships have existed for countless generations, biological research on what makes them happen has been around for a much shorter time.

The past few years have yielded a great deal of information on what makes men and women get together -- or stay apart.

First, however, a warning: A lot of the biology behind human relationships developed in eras when mating was much different than it was now, so natural instinct may not match the best decisions.

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While people may once have been most worried about passing on their genes, they may need to be more worried with keeping their spouses happy now.

So while many of these nuances of human relationships may seem to justify infidelity, they might also explain why you have feelings that don't mesh with what you know to be best here in the 21st century.

Get Tips From a Certified Sex Therapist at the ABCNews.com OnCall+ Wellness Center

As we take a look at five ways your body gives you relationship signals: don't worry too much if your ideas on relationships and the ideas here don't completely mesh. Genetics aren't destiny in life when it comes to disease, and they aren't destiny in relationships either.