A sea sponge’s sneeze lasts a very, very long time

Plus other fun facts from The Weirdest Thing I Learned This Week.
tube sponges in a coral reef

Just like when you get a whiff of stinky perfume instead of fresh air, sometimes sponges just need to sneeze something out. Deposit Photos

What’s the weirdest thing you learned this week? Well, whatever it is, we promise you’ll have an even weirder answer if you listen to PopSci’s hit podcastThe Weirdest Thing I Learned This Week hits AppleAnchor, and everywhere else you listen to podcasts every-other Wednesday morning. It’s your new favorite source for the strangest science-adjacent facts, figures, and Wikipedia spirals the editors of Popular Science can muster. If you like the stories in this post, we guarantee you’ll love the show.

Fact: Dr. Robert White did a primate head transplant—but did he transplant a soul?

By: Brandy Schillace

We tend to give precedence to the brain, and so long as our consciousness remains intact, we are we. But should we have that brain removed from the body that houses it—well, that’s another story. In fact, it’s this story. I tell the incredible story of a “Frankenstein” event, the world’s first successful primate head transplant, but also how this bizarre encounter shaped, and in fact inaugurated, life-saving technologies that still save lives today. The book will also explore a mystery that still begs to be solved: if you make a brain to live outside a body, what becomes of the self? Or as one doctor puts it, “Can you transplant the human SOUL?” And finally, this story will follow a contest every bit as determined as the space race: the Cold War contest between Russia and America to perform the first head transplant in a bid to overcome mortality and to bestow life.

Fact: Koalas have shockingly human fingerprints—but the forensic implications have been greatly exaggerated 

By Rachel Feltman

Let’s start with a supposed ‘fact’ that just isn’t true. Supposedly, back in the 90s, a spate of robberies turned out to have been committed not by a human, but by a koala—because these animals have fingerprints so similar to our own as to confuse police. 

There haven’t actually been any koala capers, as far as the record shows. This seems to have been inspired by the statement of a scientist back in the ‘90s, who pointed out that koala prints could, in theory, confuse police at crime scenes, and he figured someone should probably look into that. And in terms of purely theoretical happenings, he wasn’t wrong: You could absolutely confuse a koala’s fingerprint with a human’s, which is wild when you consider how mysterious fingerprints are to begin with.

Let’s zoom out from koalas for a minute. What exactly is a fingerprint, and why do we have them? 

Our fingerprints are made out of ridged skin that can be found on our hands and the soles of our feet, as well as on several other body parts in different mammals. They come in three major pattern categories called loops, whorls, and arches. But the idea that no two fingerprints are alike comes down to tiny shapes and changes in the characteristics of the lines within those figures, which are known as minutiae. That’s why the forensic reliability of fingerprints is more hotly debated than you might think, given that they’ve been a ubiquitous part of crime scene investigation since the early 1900s. Because the differences in fingerprints come down to loads of tiny little features, it’s very possible for an unscrupulous or biased analyzer to call something a match when it’s actually not. 

But while we can’t actually say with certainty that no two people have ever had the same fingerprints, because that’s more of a statistical question than a biological one, we do know that the amount of tiny variations that are possible in the formation of a fingerprint make it nearly, if not literally, impossible for two individuals to end up with the same set. Identical twins have more similarities between their fingerprints than fraternal twins do, and the similarities increase out from there as relations get more distant, so it’s clear there’s a genetic component. Basically, the general vibe of your fingerprint is quite heritable, but the many minutiae aren’t.

That comes down to how fingerprints form. When a fetus is about seven weeks along, its hands and feet start to form little humps called volar pads. A few weeks later, the fetus starts to grow quickly enough that those bumps just sort of fade back into the palms of its hands and feet. The shifting pressures of growing tissue seem to cause folds to form in the skin, which is how we get our whirls, arches, or loops. And which one you get depends on when, in your fetal development, your volar pads got overtaken by your growing hands and feet. That timing definitely has a genetic component, so families tend to have the same general type of fingerprint. But the formation of minutiae is way more arbitrary, and can be impacted by everything from the viscosity of your amniotic fluid to how much you punched your mom’s kidneys in utero. 

Scientists have yet to land on one concrete explanation for why fingerprints evolved, but their best guesses come down to improving our grip strength by creating friction or making us more sensitive to tactile information—there’s some evidence that the ridges of our fingerprints increase the vibrations we feel when we touch something. One 2009 study suggested that fingerprints might amplify useful vibrations while dampening others to help specialized nerve cells interpret surface texture. When that paper came out, a lot of news outlets crowd about how the “urban legend” that fingerprints existed to improve grip strength had been “debunked,” but that’s far from true. As recently as a couple of years ago, researchers were continuing to explore how these friction ridges might affect our ability to grab things, particularly when our skin is moist due to sweat. Some experts have even pointed out that an improved sense of touch could contribute to better gripping abilities, since it would help you realize when something was slipping out of your grasp, so both benefits could have been involved in fingerprint evolution. 

Let’s get back to our cuddly buddies down under. Back in the 1990s, a biological anthropologist and forensic scientist named Maciej Henneberg who’d recently come to work at the University of Adelaide was working with some koalas at a wildlife refuge when he got to looking at their digits. He was surprised he’d never read or heard anything about their fingerprints, because they looked to him to be quite human-like. He and his colleagues found some recently deceased specimens to scan with an electron microscope, and their study showed that they did indeed have a lot of similarities. 

Fingerprints show up in other primates, but koalas aren’t nearly as closely related to us as chimps and gorillas are. Marsupials branched off from primates more than 70 million years ago. So this seems to be a case of convergent evolution, meaning that what worked for primate fingers also happened to work for koala fingers. Koalas, after all, do a lot of climbing. They’re also very particular about what plants they eat, so tactile sensitivity must be useful. We see this a lot in nature—bat wings and bird wings are super similar, but didn’t actually come from a common ancestor. 

Henneberg never actually set out to catch a koala on the lam, nor did he suggest the police should actually do so. But he did point out that a crime scene could potentially be contaminated by koala prints, and the rest is history. 

I think part of the reason this sometimes gets shared as an anecdote about actual crime scenes is some rather cheeky reporting on Henneberg’s 1996 study by UK newspaper The Independent, which ran the headline “Koalas make a monkey out of the police.” The story included a local anecdote from 1975, when Hertfordshire police raided several zoos to take prints from a handful of chimps and orangutans. The guy who ordered the exercise said it was because cops used to refer to ambiguous prints as “monkey prints,” so, sure, an idiom is a great reason to go dust chimps for prints, I guess. On the bright side, zookeepers recall the chimps being happy to get the attention. This very strange side quest showed the police force that the prints were very similar, but not actually close enough to human prints to trick a trained eye—which is likely the case with koalas, too. 

I do have to dunk on The Independent circa 1996 for this one line in particular: “The chimp file is likely to be re-examined in the light of new evidence yesterday that criminal investigations in Australia may have been hampered by the presence of koala fingerprints at the scenes of crimes.” That’s based on quite literally nothing said by any of the sources quoted or referenced, and I’m pretty sure it’s what gave people the idea that primates and marsupials were under active investigation.

Fact: Sea sponges sneeze!

By: Sara Kiley Watson

It is sneeze season. And there’s plenty to make you sneeze out there–colds, the flu, allergies, you name it. 

Humans aren’t the only animals that sneeze–elephants, pandas, seals, puppies, and more all get that tickle in their nose sometimes. But not all animals sneeze—sharks for instance have nostrils and everything, but those nostrils don’t link to the back of the throat like humans do, so if they get something stuck up in their smellers they have to just try to shake it out, apparently. Aquatic animals in general don’t have the advantage of using a ton of air to push out every single annoying particle they suck up while swimming about.

However, a new study shows how one aquatic animal, in its own little way, sneezes to get rid of junk that clogs up their internal filter system—sea sponges. 

Sea sponges are some of the oldest creatures out there, with a fossil record dating back approximately 600 million years to the earliest (Precambrian) period of Earth’s history. Sponges don’t have noses, obviously. They instead have all of these tiny pores that suck in stuff from the water around them, which they use as food and nutrients. But just like when you get a whiff of stinky perfume instead of fresh air, sometimes sponges just need to sneeze something out. And sponges can’t move, so if their home all of the sudden becomes really gross, they especially need one hearty achoo. 

How their sneezes work is their little water inlets release mucus slowly over time, which builds up on their little sponge-y surfaces. When that mucus becomes too much, the sponge tissues contract and push the waste-filled snot globs into the water. Visually, it’s like pimples popping themselves, so if that’s your thing then you’ll be a big fan of the sponge sneeze.