6 Traits Humans Inherited From Fish

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ThinkStock

What’s so fishy about human anatomy? A lot! Just look at these gifts from our aquatic ancestors.

1. Embryos

Look closely at any mammal, bird, or amphibian embryo—they all look the same. That’s because they all inherited genes from a common, fishy ancestor. During the middle stage of development—called the phylotypic period—a special combination of those genes becomes active, while some get turned off. Those active genes become the blueprints for your body.

2. Our Voice

Fish can’t talk, but they do have gills—and that’s where our voices come from. Just like fish, human embryos have gill arches (bony loops in the embryo’s neck). In fish, those arches become part of the gill apparatus. But in humans, our genes steer them in a different direction. Those gill arches become the bones of your lower jaw, middle ear, and voice box.

3. Sense of Hearing

How did gills become part of the ear? Just look at the fossil evidence. The ancient fish Eusthenopteron lived about 370 million years ago. It had a problem, though: A small part of the jawbone—the hyomandibula—poked into its gills. A few million years later, that same pesky bone formed a cavity by the ear of Eusthenopteron’s descendents. There, it started amplifying sound—travel down the fossil record even further, and you’ll see that the bone had become the stape, the part of the ear that helps us hear.

4. Hernias

Fish gonads sit near the heart. In human embryos, the gonads form deep in the chest—just like in fish. However, since we’re warm-blooded, these gonads need to go somewhere cool. After 12 weeks, they start to descend, and for men, they break through the body wall and form testicles. But breaking through the body wall leaves behind a weak spot, which is why it’s relatively easy for humans to get hernias.

5. Fingers

Fish don’t have fingers, but they do have the gene that makes fingers possible. In the 1980s, scientists discovered a special gene called “sonic hedgehog,” which helps animals form digits. When scientists mutated sonic hedgehog in various animals, the creatures all grew extra fins and fingers (people with polydactylism—that is, six fingers—suffer from a sonic hedgehog overload). A surge in sonic hedgehog helped ancient fish crawl onto land.

6. Our Faces

You know that groove above your upper lip, just below the nose? That’s the philtrum. It’s there because, as an embryo, your face looked kind of fishy. Your eyes started at the side of your head and your nostrils and lips grew at the top (you looked a little like an eel). After a couple of months, those features migrated: Your eyes squeezed inward while your lips and nose dropped. The transformation left behind a tiny divot above your upper lip, and gave men everywhere a place to grow terrible mustaches.

What’s That Thing That Hangs Off a Turkey’s Face?

iStock.com/JZHunt
iStock.com/JZHunt

That thing is called a snood. And it's there to let the other turkeys know that its owner is kind of a big deal.

When a male turkey—known as a tom—wants to mate, he faces two hurdles. One is his potential mates, the female turkeys (a.k.a. hens). In the realm of turkey mating, the hens wield the power of choice and the toms have to get their attention and win the opportunity to reproduce. Come mating season, a tom will strut around, gobble, puff out his chest, fan his tail, and drag his wings to attract the hens, who then pick which of the toms they’ll mate with.

The second problem for a tom looking for love is the other toms in the area. They’re all competing for the same limited number of hens. Sometimes a good mating display isn’t enough to win a mate, and toms will attack and fight each other to secure a hen. 

This is where the snood comes in. That goofy-looking piece of dangling flesh helps a tom both with choosy hens and with competition from rival males. Having a long snood almost always means that a hen will want to mate with him and that another tom will back down from a fight.

DUDES AND THEIR SNOODS

When two toms are trying to establish dominance, they’ll size each other up. Then they'll either fight, or one will flee.

In the late 1990s, Richard Buchholz, an animal behaviorist who focuses on turkeys, wanted to figure out which, if any, characteristics of a tom turkey could predict how they fare in dominance fights. That is, did bigger turkeys tend to win more scuffles? Did older ones? He also wanted to see if the turkeys used any of these predictive cues when sizing each other up. He looked at various characteristics of dominant toms that fight and win, and compared them to those of subordinate toms that lose fights or run from them. Of all the characteristics he looked at, only “relaxed snood length” seemed to be a reliable predictor of how a tom would do in bird-vs-bird combat. The dominant males, the ones who won fights and got a choice mate, had longer snoods.

With that in mind, Buchholz looked at how toms reacted to other toms with snoods of varying sizes. The birds tended to avoid confrontation with other males with longer snoods, and wouldn’t even feed near them. A big snood, this suggests, says to the other turkeys that this is a tom you don’t want to tangle with. Buchholz noted that snood length correlates with age, body mass, and testosterone, so, to competitors, the snood could be a good indicator of a tom’s aggressiveness, age/experience, size, and overall condition and fighting ability.

IN THE SNOOD FOR LOVE

Once the males have established who’s going to have a chance to mate, the final choice goes to the hen. While the mating display is the main draw for getting a hen to check him out, a tom’s snood helps him out again here.

Like it did for the other males, a tom’s snood signals a lot of information to a female assessing potential mates—it indicates how old and how big he is, and even says something about his health. In another study, Buchholz found that longer-snooded toms carried fewer parasites. If a hen wanted to choose a mate with good genes that might help her offspring grow large, live long, and avoid parasites, a tom’s snood is a good advertisement for his genes. In that study, hens showed a clear preference for toms with longer snoods. In another experiment years later, Buchholz found that healthy hens again showed a strong preference for long snoods and that hens with their own parasite problems were less picky about snood length and checked out more potential mates—perhaps, Buchholz thinks, because the hens recognized their own susceptibility to infection and were willing to invest more time searching for a tom with genes for parasite resistance that would complement their own—but still showed some preference for longer ones.

While a snood might look goofy to us, for a turkey, it’s integral to the mating game, signaling to other toms that they should get out of his way and letting hens know that he’s got what they’re looking for.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

An earlier version of this article ran in 2013.

9 Not-So-Pesky Facts About Termites

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iStock.com/Thithawat_s

Termites get a lot of hate for chewing through buildings, but the little creatures are far more interesting—and ecologically valuable—than we often give them credit for. Unless, of course, you’re Lisa Margonelli, the author of Underbug: An Obsessive Tale of Termites and Terminology, a new book that explores their amazing world. Here are nine facts about the highly social—and occasionally pesky—insects that we learned from the book.

1. THERE ARE FAR MORE TERMITES THAN PEOPLE ON EARTH.

Termite queens live up to 25 years, and can lay somewhere around 30,000 eggs a day. As a result, a single mound can be home to millions of individuals at a time. While the numbers vary from study to study, scientists estimate that the biomass of all the termites in the world is at least as great as that of humans.

2. MOST TERMITES AREN’T PESTS.

Of the 2800 named termite species in the world, the majority have no interest in eating your house. Only 28 species are known to chow down on buildings and infrastructure. Most are actually very beneficial to their ecosystems, clearing dead wood, aerating the soil with their intricate tunnel systems, and enhancing plant growth. Researchers have found that contrary to being pests, networks of termite mounds can help make dry environments like savannas more resilient to climate change because of the way termite mounds store nutrients and moisture, among other benefits.

3. TERMITES ARE GOOD FOR CROPS.

Termites can help make soil more fertile. In one study, researchers in Australia found that fields that were home to ants and termites produced 36 percent more wheat, without fertilizer, compared to non-termite fields. Why? Termites help fertilize the soil naturally—their poop, which they use to plaster their tunnels, is full of nitrogen. Their intricate system of underground tunnels also helps rainfall penetrate the soil more deeply, which reduces the amount of moisture that evaporates from the dirt and makes it more likely that the water can be taken up by plants.

4. TERMITES HAVE VERY SPECIFIC ROLES IN THEIR COLONY.

Each termite colony has a queen and king termite (or several), plus workers and soldiers. This caste system, controlled by pheromones produced by the reigning queen, determines not just what different termites do in the colony but how they look. Queens and kings develop wings that, when they’re sexually mature, they use to fly away from their original nest to reproduce and start their own colony. Once they land at the site of their new colony, queens and kings snap off these wings, since they’ll spend the rest of their lives underground. Queens are also physically much larger than other castes: The largest type of termite, an African species called Macrotermes bellicosus, produces queens up to 4 inches long.

Unlike their royal counterparts, most workers and soldiers don’t have either eyes or wings. Worker termites, which are responsible for foraging, building tunnels, and feeding the other castes in the nest, are significantly smaller than queens. M. bellicosus workers, for instance, measure around 0.14 inches. Soldier termites are slightly bigger than workers, with large, sharp mandibles designed to slice up ants and other enemies that might invade the nest.

5. TERMITES ARE ONE OF THE FASTEST ANIMALS IN THE WORLD.

Apologies to cheetahs, but termites hold the record for world’s fastest animal movement. Panamanian termites can clap their mandibles shut at 157 miles per hour. (Compare that to the cheetah’s run, which tops out at about 76 miles per hour.) This quick action allows tiny termite soldiers in narrow tunnels to kill invaders with a single bite.

6. TERMITES ARE SKILLED ARCHITECTS.

In Namibia, quarter-inch-long termites of the genus Macrotermes can move 364 pounds of dirt and 3300 pounds of water each year total in the course of building their 17-foot-tall mounds. Relative to their size, that’s the equivalent of humans building the 163 floors of Dubai’s Burj Khalifa, no cranes required. And that’s not even the tallest termite mound around—some can be up to 30 feet high. More impressively, termites cooperate to build these structures without any sort of centralized plan. Engineers are now trying to replicate this decentralized swarm intelligence to build robots that could erect buildings in a similar fashion.

7. TERMITES BUILD THEIR OWN AIR CONDITIONING.

Some termites have developed an incredibly efficient method of climate control in the form of tall, above-ground mounds that sit above their nests. Organized around a central chimney, the structures essentially act as giant lungs, "breathing" air in and out as the temperature outside changes in relation to the temperature inside. Thanks to these convection cycles, termites keep underground temperatures in their nest between roughly 84°F and 90°F.

8. TERMITES ARE FARMERS.

Humans aren’t the only ones cultivating crops. Termites farm, too. They’ve been doing it for more than 25 million years, compared to humans’ 23,000 years. Some species of termite have evolved a symbiotic relationship with Termitomyces fungi, growing fungus in underground gardens for food. When they fly off to create a new colony, termite queens bring along fungus spores from their parent colony to seed the garden that will feed their new nest. Foraging termite workers go out and eat plant material that they can’t fully digest on their own, then deposit their feces on the fungus for it to feed on. They can then eat the fungus. They may also be able to eat some of the plant material after the fungus has sufficiently broken it down. The mutually beneficial relationship has led some scientists to suggest that the fungus, which is much larger in both size and energy production than the termites, could in fact be the one in control of the relationship, potentially releasing chemical pheromones that lead the termites to build the mound they live in together.

9. TERMITES ARE MICROBIAL GOLD MINES.

As scientists begin to understand the huge role that micobiomes play in both the human body and the rest of the world, termites provide a fascinating case study. About 90 percent of the organisms in termite guts aren’t found anywhere else on Earth. In their hindgut alone, they host as many as 1400 species of bacteria. These microbes are so efficient at converting the cellulose-rich wood and dead grass that termites eat into energy, scientists want to harness them to make biofuel from plants.

Want to learn more about termites? Get yourself a copy of Underbug on Amazon for $18.

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