Antonio Manaligod/Dose

Hookup culture just collided with procreation?—?and it’s bad.

About half the sperm banks in the UK have adopted an app called London Sperm Bank Donors that lets prospective mothers swipe through prospective male donors until they find one they like. The app, nicknamed “order a daddy,” boasts “more than 25,000 vials of donor sperm at any given time.” Moms-to-be can make a wishlist of traits they’re looking for in a donor. When they select a donor, they make an in-app purchase of 950 pounds, or $1210 in US currency, and pow! The sperm is dropped off at a fertility clinic, waiting for insemination.

Sounds fun, right? Well, maybe—but in reality, choosing a partner with whom to procreate is anything but a game. In fact, it’s our prime biological imperative, and over millions of years our bodies have developed sophisticated mechanisms to make sure we make the proper selection. All of our senses are involved.

When we meet a prospective partner, our eyes scan his or her face, but it doesn’t stop there. We analyze that person’s height and weight. Our ears listen to their voice. Our touch feels their skin. Our noses detect airborne hormones called pheromones, secreted in sweat and urine. (I know, gross.)

These chemical signals can tell us if they’re healthy, and the right sexual fit. Men can even smell when a woman is most fertile.

Psychologist Devendra Singh told ABC News,

“When women are ovulating, they dress better, and they feel better and more attractive. They are more intrigued by erotica, and more sociable.”

Singh says ovulating women may thus appear more confident, and our own experience shows women tend to pick confident men, too.

We humans use a combination of senses, and our brain, to judge demeanor. We watch a prospective partner’s body language, how they walk. And just imagine all the data we collect when we kiss someone.

“Come closer. I want to smell your genes.” | Toa Heftiba/Unsplash

Reading this sensory information is part of how we fall in love, which may explain why a Tinder hookup can be fun for a night but is often thrown out with the next morning’s trash. It’s also how we detect infertility and disease—and preserve the future of the human race. In fact, several studies have shown that humans can smell a variety of diseases in others, including tuberculosis, yellow fever and many more.

Of course, any man on a sperm bank’s app is going to be fertile and screened for major diseases. But what about genetic conflicts or mutations? If humans can smell disease, is there a chance we can detect genetic incompatibility as well? We know mice can, and some scientists think we can, too. Can we really trust an app to do the same? And should we risk it?

There’s another, equally scary implication of choosing mates by swiping: an unintended shrinking of the gene pool. Several studies show that as men and women use online dating apps and sites more and more, we’re getting more and more prejudiced. Over five years of studying more than 25 million people, dating site OKCupid found women are more likely to choose a man of their own race.

Here’s how it breaks down: According to the data, white women think white men are the most attractive. After that, they prefer Latino men. They find black and Asian men less attractive.

Black women find anyone but black men less attractive, but have started to rate Asian men as attractive, too. Asian women find blacks and Latinos less attractive—and strongly prefer white men over Asian men.

As for the men, Asian men show a preference for Asian women. Black men show a preference for Latina and Asian women, while Latino men rank Asian and Latina women the highest. White males show a marked preference for Asian women, with the numbers decreasing in their preference for Latina and then white women.

Sounds pretty awful, right? But don’t lose heart. While all this data shows that online or app daters are getting more biased, not less, these prejudices are at odds with dating in real life: More and more mixed-race couples fall in love every day, and research even shows they’re happier.

If more women choose sperm donors online, it’s possible they’ll be influenced by the same kinds of unconscious prejudices that are increasingly visible in the data on our online dating habits. This could lead inevitably to a narrowing of the gene pool. And we have to ask ourselves: Is this the kind of future we want to be building?