Gorillas talk a big game, what with all their chest thumping and basically continuous farting. But there’s one very specific, very human metric by which they come up humiliatingly short – literally. That’s right: it’s dick time again. 

Your basic silverback gorilla, whether Eastern or Western, will be up to 1.8 meters tall and 200 kilograms in weight. For Americans, that’s the equivalent of a 5.9-foot-tall, 441-pound dude, built of so much pure muscle that it can lift more than 800 kilos (1,763 pounds, or around two grand pianos) without breaking a sweat.

“It’s hard to measure how strong a gorilla really is, but estimates range from around 4x – 10x stronger than your average human,” notes BBC Wildlife Magazine’s Gorilla Guide. “A silverback gorilla’s strength is certainly formidable. All gorillas can tear down banana trees without trying too hard, they’ve escaped from cages by bending the iron bars, and they have a bite force of around 1300 psi [9 MPa], double that of a lion.”

It’s all very intimidating, and seemingly at odds with another fun gorilla fact that you may not be aware of: that gorillas, as mighty as they are, have the smallest penises in the entire ape family. In fact, it’s the smallest relative to body size of any mammal.

Now, we’re all about equal opportunity dick sizes here at IFLScience, but the miniature nature of the gorilla phallus really is noteworthy. At around 3 centimeters (1.1 inches) long, it’s shorter than the average for a newborn baby in humans, and far smaller than the cut-off for a human micro-penis.

Not only are they the least well-endowed of the family in terms of the, uh, length of their equipment, but they’re also pretty lacking in the ball department too. Their testes are small, their sperm count is low, and even those little swimmers they do shoot out are pretty poor at their actual job: “gorilla sperm [has] extremely low mitochondrial function[…] slow swimming speed and weak swimming force,” explained one study, published earlier this year in the journal eLife. 

“Gorillas also have […] a large proportion of immotile and morphologically abnormal sperm,” the authors continued. “Gorilla sperm also bind the egg’s zona pellucida more weakly than other species.”

In fact, so baked-in to the gorilla genome are these underwhelming features that they could now helping our own species to multiply. In that same study, researchers were able to match up certain genes in gorillas with their equivalent in humans, finding that many were markedly enriched in men with low-to-no sperm counts. 

Basically, gorillas are nature’s one-shot argument against “big dick energy” having anything to do with actual physiology – and a big “suck it, idiots” to the entire manosphere crowd. 

Which is great and all, but it does make us wonder: why?

Why are gorilla penises so tiny?

It may strike you as odd that a silverback gorilla – literally the hugest, most powerful, most literally “alpha” primate there is – would have such minute genitalia. As counterintuitive as it may seem, though, the two facts are actually intrinsically linked: “the male gorilla’s huge stature is in fact the reason why he has such a small penis,” explained Suzanne Harvey, now Head of Schools, Impact, and National Partnerships at the Royal Institution, in a 2012 article for UCL.

Why? It’s simple, really: gorilla societies are both strictly hierarchical and almost always polygynous – that is, there is a single dominant male, and he has sole mating rights with all the females in the group. Basically, their genitals are small because they have no need to be big: “when competition between males occurs through physical aggression, an alpha male may fight off rivals and control his own mating success without the need for sperm competition,” Harvey wrote. “Other physically smaller males have little access to females in the group.” 

Compare gorillas to their big-balled chimpanzee cousins, and the picture becomes even clearer. Chimps, unlike gorillas, “live in large multi-male, multi-female groups, where females are able to mate with many males,” Harvey explained. “Sperm can live for up to four days after ejaculation, and consequently when females mate with two males in close succession, sperm from two males can be in direct competition.”

If you’re a male chimp hoping to spurt your DNA into the next generation, then, it’s in your best interest to produce powerful, efficient sperm – and lots of it. The result: a pair of massive testes, more than a third the weight of the chimp’s brain – humans’ come in at less than three percent, for comparison – capable of producing vast amounts of sperm, many times a day.

And yes, we know exactly what you’re thinking…

How do humans measure up?

So, on the scale from “gorilla” to “chimp”, where do humans come? Well, weirdly, it’s kind of a paradox.

“Humans have a much longer and wider penis than the other great apes,” wrote Mark Maslin, a professor of Palaeoclimatology at UCL (a hotspot for this area of research, apparently), in a 2017 article for The Conversation. However, “our testicles are rather small […] and produce a relatively small amount of sperm.”

Other mating characteristics are equally mismatched in our species. While the human penis may be big, Maslin noted, it’s also “extremely dull – it does not have lumps, ridges, flanges, kinks or any other exciting feature that other primates have.” 

That’s not just empty negging: in primates, a boring dick usually a sign that a species is monogamous – and it’s therefore strange to find on humans, Maslin explained. “[It] clashes with the fact that men are significantly larger than women,” he wrote, since that “suggests our evolutionary background involved a significant degree of polygynous, rather than exclusively monogamous, mating.”

There have been many attempts to reconcile these two competing impressions of our species – perhaps men are bigger than women to help protect our laughably pathetic offspring; maybe the supposedly “dull” human penis has a secret weapon in its coronal ridge. But in the end, Maslin suggests, trying to explain humans’ weird genitalia through the lens of wider great ape biology may be the wrong tactic entirely.

“If we view the evolution of monogamy mating systems in humans through the lens of human society it is clear that it takes a huge amount of social effort to maintain and protect more than one mate at a time,” he wrote. “It is only when males have access to additional resources and power that they can protect multiple females, usually by ensuring other males protect them.”

Basically, he explained, it takes a lot of resources and prestige to be able to take on multiple partners as a human – so the solution for most on an individual level has become to simply not. Monogamy becomes culturally endorsed, save for a select few who can afford – or get away with – supporting more.

In other words, Maslin concluded, “in complex human societies the largest and most important sexual organ is the brain.” While gorillas may beat their chests to prove their dominance, male humans might flaunt their cash or wit or good looks; whereas chimps must rely on buckets of spunk to further their family, humans tend to couple up long-term based on personal or social factors.

“Somewhere in our evolutionary past how smart and social we are became the major control on our access to sexual partners,” Maslin wrote. “Not how big or fancy a male’s penis is.”