A professor at Missouri State University has halted a study on the relationship between penis size and self-esteem following an enormous public response she says has compromised the reliability of her research.

Amazon has been using its current logo for 18 years. The online retailer started using the logo in June 2000, shortly after it expanded beyond selling books. The logo shows the company’s name, with an arrow that points from the “A” to the “Z” in the name.

HIV transmission is a complex process with factors beyond just who you sleep with and how. The virus ultimately needs to find its way to the correct kinds of cells in order to wreak havoc. And some of the risk, at least for those with penises, may come from the kinds of bacteria on the tip.

Although we call erections “boners,” anyone who has basic familiarity with human anatomy knows our slang deceives us—for unlike most mammals, men have no penis bones. For decades scientists have wondered, “Why? No? Penis Bone?” A new study published in Proceedings of the Royal Society might finally answer the mystery…

Researchers working in Burma have uncovered the fossilized remains of a 99-million-year old male daddy longlegs with its penis fully extended and erect. It’s possibly the oldest—and longest held—erection in the history of science.

Just in time for Halloween, University of Glasgow medical student Mike McCormick released diagrams of the female and male reproductive systems made out of all the kinds of candy I hated to get when I went trick-or-treating as a kid.

Cat sex videos are all the same. The tom mounts the female, she arches her back and moves her tail aside–a response called lordosis, by the way–and the two of them get down to the act. But soon afterwards, the yowling starts, followed by the spitting and swiping. Why so angry, kittycat?

The tuatara isn’t actually a lizard. It’s the last survivor of a 250 million year old group of reptiles that mostly went extinct with the dinosaurs. It doesn’t have a penis, and ironically, that’s made it a linchpin for understanding how penises evolved in vertebrates.

Ejaculation may feel like a glorious mess, as uncontrollable as an avalanche or a runaway train. In reality, it’s a tightly choreographed court dance: integrating three different branches of the nervous system, triggering cascades of contractions in smooth and striated muscles, all accompanied by the electrical storm…

Some mammals have a dangerous-looking penis because their glans is covered in spines. In a few cases, we know why they’re there (typically, to induce ovulation during copulation). But in many other species, the purpose of the spiky bits is something of a mystery.

Guys, imagine for a moment what life would be like if you couldn’t feel your penis. That can happen to men with some kinds of spinal injuries, or who were born with a condition called spina bifida. Their penises can still sense touch, but a break in the spinal cord means the signal never makes it to the brain.

If you’ve ever watched a pair of dogs have sex, you’ve probably noticed something odd happen partway through the act. At first, the male grips the female’s back and humps away–nothing unusual about it. But then he dismounts and turns to face away from his mate, with his penis still stuck inside her.

Sea slugs are beautiful, jewel-like animals with surprisingly violent mating habits. This tiny unnamed species in the genus Siphopteron is no different.