Human Birth Control Pills Work on Gorillas

If you've ever wondered just how similar humans are to gorillas, here's a surprising piece of evidence: the same birth control pills you can pick up at a pharmacy work perfectly on gorillas. Zoos around the world routinely give female gorillas combination birth control pills—the exact same formulation humans use—to prevent unwanted pregnancies and manage captive populations.

Female gorillas can become reproductively mature as young as 4 to 6 years old. Without contraception, zoos would face serious overcrowding issues and challenges in maintaining genetic diversity. Rather than developing specialized primate contraceptives, zookeepers discovered that human birth control pills do the job perfectly.

How Zoos Administer the Pills

There's just one catch: gorillas aren't great at swallowing pills on command. Zookeepers get creative by crushing the pills and mixing them into treats like yogurt, honey, or oatmeal. The documented failures of gorilla birth control are usually traced back to one simple problem—the gorilla didn't actually swallow the pill.

Research published in peer-reviewed journals confirms that these contraceptives work by eliminating the ovarian cycle, keeping hormone levels below the baseline needed for reproduction. It's the same mechanism that works in humans, just applied to our 98.3% genetically similar cousins.

The Evolutionary Connection

This biological compatibility shouldn't be too shocking when you consider the facts:

• Humans and gorillas share about 98.3% of their DNA
• We diverged from a common ancestor only 10 million years ago (a blink in evolutionary time)
• Our reproductive systems evolved from the same basic primate blueprint

The fact that the same hormonal contraceptives work on both species is powerful evidence of our close evolutionary relationship. The hormones in birth control pills—synthetic versions of estrogen and progesterone—interact with gorilla biology in essentially the same way they interact with human biology.

It Works Both Ways

The biological similarity runs in both directions. When zoos want to encourage gorilla pregnancies, they sometimes use human fertility drugs like clomifene to stimulate ovulation. In 2007, a western lowland gorilla at a zoo in southwest England gave birth after being treated with this human fertility medication.

While the contraceptives are highly effective, researchers have discovered they can affect gorilla behavior. Studies show that birth control can alter the timing of sexual displays and estrous behavior, though these behaviors occur in less than 1% of observations in contracepted females. Scientists continue studying these effects to ensure the medications don't negatively impact gorilla welfare or social dynamics.

So the next time you're at a zoo observing gorillas, remember: those females might be on the exact same birth control as millions of human women. It's a daily reminder that we're not as different from our great ape relatives as we might think.