The Providence Journal / Tom Murphy

Maybe looks matter in a mate, but so, apparently, do cute chromosomes. Call it DNA dating.

Eric Holzle, however, calls the concept Scientificmatch.com. It’s his new online dating service. As with many such services, it matches people based on personality and values. But unlike other services, it also matches people based on biochemical compatibility.

This involves genetic testing. Call it the science of romance: finding genes that fit.

“It’s a very critical piece of the puzzle, but not the only piece,” Holzle says. “But it’s the only piece of the match-making puzzle that has been scientifically proven” in studies from researchers at institutions including Yale, the University of Colorado and the University of New Mexico.

The premise behind the science is that people with different immune systems are naturally attracted to each other. The thinking is their offspring will have greater genetic diversity, and, therefore, better health. But in addition, Holzle says, studies show that people who are biochemically different, and therefore compatible, are more sexually satisfied with each other, and more faithful to each other.

“Just because you have physical chemistry with someone does not mean you’ll have a great relationship with the person,” Holzle says. “But without physical chemistry, a long-term relationship is not worth pursuing.”

Holzle, 43, who was raised in Connecticut and schooled in Massachusetts, at Northeastern University and Babson College, started his company last month. While he says his intention is to take his business nationwide, he has started it with just one market: the Providence-to-Boston area.

“It’s a very intelligent area,” Holzle says. “I would think the people would understand the service more than in other parts of the country.”

The service is based on science. That’s because Holzle is a scientist, an engineer with an MBA.

“People cringe when they hear that. Engineers are not the most socially adept creatures. A lot of people would not expect to go to a mechanical engineer when they’re looking for the love of their life.”

Holzle, who has never married and has used many online dating services, got the idea for his company five years ago. He saw a TV documentary about a 1995 Swiss study commonly called the “Sweaty T-Shirt Experiment.” In the experiment, a group of women evaluated the smell of T-shirts worn three consecutive days by men, who did not use colognes or deodorants. All people, except identical twins, have different genetic codes for their immune systems. And when we sweat, we emit a smell that’s particular to us and reflective of our immune system. The study found that the women were attracted to the T-shirts of men who were immunologically different from them, and were unattracted to the ones of men who were immunologically similar to them.

The documentary repeated the experiment, reversing the gender roles, and “the results were phenomenal,” Holzle says.

The Sweaty T-Shirt Experiment is well known among researchers. Rachel Herz, a professor of psychology at Brown University, studies the effects of smells on human emotions and behaviors. Last fall, Herz published a book, The Scent of Desire, supporting the connection between smell and interpersonal attraction.

When Herz recently heard about Holzle’s dating service, she said that five years ago she thought to start a similar service.

“I think it’s a good idea,” Herz says, though her approach would have been more faithful to the T-shirt experiment. Dating service members would narrow their selection to a few candidates, whose clean but worn T-shirts they’d receive in the mail to smell.

But her informal market research wasn’t encouraging.

“Women said, ‘Eeeuw, I don’t want to smell some guy’s T-shirt.’ The men said, ‘Sure, I’ll smell her T-shirt. Send me anything.’ I think his (Holzle) way gets around this.” But, she says, it also removes personal experience from the process.

Herz prefers personal evaluation over scientific testing. And the DNA testing in Scientificmatch, she says, is based on a small percentage of the more than 50 genes that are known to make up our immune systems.

Holzle admits that Scientificmatch’s DNA testing, which is based on mail-in saliva swab kits, involves tests of only six genes. But these six genes, he says, are the ones most variable in our immune systems, and, consequently, the ones most used by researchers.

“Attraction is like an aphrodisiac,” he says. “When you have chemistry, it’s literally that person’s sweat giving off an aphrodisiac that applies to those with compatible immune systems.”

Anecdotally, Holzle says he has experienced both aspects of this idea. He remembers once meeting a very attractive woman and feeling completely unattracted to her.

“I just didn’t feel a big sexual spark talking to this person. She seemed intelligent and we agreed on issues. But it felt more like I was talking to my sister.”

Similarly, he recalls once finding himself attracted to a physically unattractive woman.

“There was a distinct sexual spark. In retrospect, the reason must boil down to our immune system genes.”

The key to chemical attraction, Holzle says, is being able to smell each other’s natural chemicals, which is increasingly rare, which is one reason his company resorts to testing.

While Holzle says genetic testing is important in finding long-term compatibility, he says it’s not the only criterion. So Scientificmatch uses two other criteria: personal preferences and values. The latter is largely measured by having people rank the importance of six values: education, spirituality, pragmatism, friendship, status and visual appearance.

“The theory is people with the same fundamental profile will get along best,” he says.

Holzle won’t disclose the number of people who have so far joined his service, for $1,995.95 a year, which covers the cost of DNA testing and conducting background checks.

“Most of our members are interested in long-term relationships. That could be a function of the cost of our service. There is a correlation between how much someone is willing to pay for a dating service and the type of relationship they’re looking for.”