Researchers at the University of California, Berkeley, may have unraveled one of the mysteries involving human sperm, one that could open up a new avenue for enhancing, or even suppressing, male fertility.

The discovery revolves around the sperm’s last ditch, no-holds-barred effort to reach an unfertilized egg.

The phenomenon is known as hyperactivation. It’s the extra “oomph” that sperm need to burrow through the egg’s many defenses.

The Berkeley researchers figured out the complicated chemical cascade that starts with sperm sniffing progesterone, a hormone secreted by the egg.

It ends with the sperm trying to force their way through the egg’s barrier like a SWAT team trying to break down a heavy door.

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Unisex Birth Control

This process all relies on an enzyme called ABHD2.

When progesterone binds to ABHD2 on the sperm’s tail, it breaks open an ion channel that’s also embedded in the tail.

Once open, that channel allows calcium ions to flood in, powering the sperm in its final rush to the egg.

Now that we understand how sperm and progesterone interact, the researchers say, we can block that interaction, leading to male or even unisex birth control.

Despite widespread interest, the male birth control pill has remained elusive. That’s for a variety of reasons, not least of which is that it is a challenging scientific pursuit.

While the female birth control pill mimics natural periods of infertility (such as pregnancy and breastfeeding) there is no such natural infertility to mimic in men.

Plus, male birth control would have millions of targets, rather than just the one to several eggs a woman releases each month. By some estimates, men produce about a thousand sperm for every heartbeat.

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Stopping Sperm Along the Way

The key to male birth control probably lies somewhere on the sperm assembly line.

Think of a sperm as a mail carrier delivering a package, Melissa Miller, Ph.D., the study’s first author, told Healthline.

“He has to get out of the post office and reach your house and it doesn’t matter if his truck breaks down still at the post office or whether it breaks down en route to your house,” Miller said, “your package is still not going to get delivered.”

If we disable the enzyme from interacting with the progesterone surrounding the egg, Miller said, the sperm’s long journey up the reproductive tract would end in failure. The mail carrier, in essence, would be stopped at the front door.

Miller thinks that a drug acting on this pathway could potentially be administered to men or women. In women, the drug would hang around the reproductive tract, becoming active in the presence of sperm.

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Developing a Drug

But the reality of such a drug is a long way off.

Like any drug, development is a long and arduous process, and contraceptives are held to high standards.

“What you have to do is actually be able to control it,” John Townsend, Ph.D., director of the Reproductive Health program at the Population Council, told Healthline. “You have to be able to turn it on and turn it off. You have to have efficacy levels of at least 93 percent.”

And however it’s delivered, whether gel, injection, or pill, it would have to be acceptable to people.

To be developed for the real world, tested for safety and reliability, and manufactured inexpensively—“that’s probably a 20-year process,” Townsend said.

But that doesn’t mean it’s not a worthwhile pursuit, he added.

“There is no reason why women should bear the burden of responsibility and cost of this,” he said.

While options for women have multiplied since the 1960s to include a variety of pills, shots, and implants, men’s options haven’t changed much since the development of the vasectomy.

According to Planned Parenthood, men who have vaginal intercourse with their partners have three options to avoid pregnancy: condoms, withdrawal, and vasectomy. In contrast, women have about a dozen options.

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Would Men Use It?

Male willingness to try novel birth control methods ranges from 28 percent to 75 percent, according to surveys. That variation comes from cultural differences and the type of hypothetical contraception being described.

Some promising projects in the pipeline include Vasalgel, a polymer that would be injected and then rinsed away when men want to have children. There’s also a “clean sheets pill” that would prevent any seminal fluid from leaving the penis, potentially preventing sexually transmitted infection as well as pregnancy.

On the flipside, the Berkeley discovery also helps explain some of the most puzzling cases of male infertility, where sperm count is high and the sperm themselves are shaped correctly and seem to swim normally.

That’s true for more than 80 percent of men who are deemed infertile, said Miller.

For some of these men, “it might be that this specific protein just is mutated in some way that it can’t recognize progesterone.”

A test that screens for such a mutation could give much needed answers to couples having trouble getting pregnant.