A new dating site moves beyond E-Harmony’s “science of love” to require saliva samples to test DNA for two key markers for compatibility.

SingldOut.com mails users a DNA-testing kit to submit a saliva sample, which is then tested at a laborotory for the presence of two genetic markers, including one for the serotonin uptake controller influential over how people control their emotions. The other marker is associated with genes influencing the immune system.

"With online dating, you have socioeconomic factors people try to match on — religion, how much you make," Ron Gonzalez, co-founder of Instant Chemistry, told USA Today. "This is another layer on top of that so you can better find matches."

Within a week of joining the site, administrators post the user’s test results on his or her profile for comparison with other users. Instant Chemistry, the manufacturer of the DNA tests used by the dating site, believes its research shows a strong link between those two genetic markers and long-term compatibility in a relationship. People with different, complementary versions of the serotonin and immune systems were most compatible, the company says.

The dating site says human pheromones may allow people to find compatible mates, although the process requires a kick-start to work online — where men and women remain mostly relegated to personality inventories, bios, photos, and favorite quotes as a way to “sniff out” potential mates. In the greater offline world, men depend on visual cues as well as pheromones to find their perfect match. At first glance, a 0.7 hip-to-waist ratio suggests optimum biological health to the male gaze.

Conversely, women depend on the same sensory cues while searching according to their own requirements, finding men with angular facial features most attractive, as it implies subconscious clues about testosterone production and reproductive health, as well as the ability to protect family and control resources.

Although the new site requires only saliva sample testing, the bar for online matchmaking has just been raised.