Cats Didn't Need Our Help to Become Domesticated

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Among domestic animals, cats are best known for their independence. With good reason: They have been living alongside humans for far longer than they've been domesticated. Felines lived side by side with humans for thousands of years before we finally began to influence their breeding, according to new research (via Smithsonian). Whereas it has been 40,000-odd years since we started domesticating dogs, selective breeding of cats may have started only in the medieval era.

Writing in Nature Ecology and Evolution, scientists from the University of Leuven in Belgium and the Institut Jacques Monod in Paris (among many other institutions) analyzed cat DNA from ancient and modern cats from Europe, north and east Africa, and southwest Asia, looking at samples dating back 9000 years. They got their samples from the bones and teeth from more than 200 cat remains from Stone Age sites, Viking graves, and Egyptian tombs.

There is plenty of evidence that cats and humans have lived together for millennia, like a cat skeleton buried with a person in Cyprus around 7500 BCE and skeletons of cats buried in an Egyptian cemetery from around 3700 BCE. But the "evidence points to a commensal relationship between cats and humans lasting thousands of years before humans exerted substantial influence on their breeding," they write.

Domestication came in two waves, according to this research. Of five different subspecies of wildcat that originated all over the world, domestic cats only belong to one: Felis silvestris lybica, the African wildcat. When the first farmers in the Fertile Crescent began to store grain from their fields, wildcats flocked to hunt the mice that were attracted to the food stores. Farmers likely began to tame these cats, realizing that they could keep rodents away from the food supply. These cats from the Middle East then started to spread into Europe.

Several thousand years later, ancient Egyptian cats began to spread out across what is now Turkey, Bulgaria, and other places, becoming a more common type than the Middle Eastern cats that had previously dominated the population. Egyptian cats traveled throughout the world thanks to shipping, because boats needed feline sailors to keep rats from chewing through their ropes and eating their food on board. Egyptian cat DNA showed up in samples from as far north as a Viking port on the Baltic Sea, so it's likely that they were taken on trade routes to northern Europe.

Unlike with dogs, though, it seems that people were employing cats as mousers but not selecting specific aesthetic traits. People haven't been breeding cats until quite recently—just about 700 years ago. In order to pinpoint the spread of domestication by humans (which is a contentious thing to define, as house cats are still very similar genetically to their wild cousins), the researchers followed the spread of the genetic change that leads to blotched tabby markings; because the coloration is due to a recessive gene mutation, its proliferation was probably due to humans breeding for that pattern. (It doesn't show up in wildcat populations.) According to the scientists' samples, the allele for this pattern didn't show up until the medieval era, around 1300 CE, when it was present in what is now Turkey. It would take a long time before humans really began choosing their cats for their appearance. Breeding for looks didn't really take off until the 19th century.

Even now, cats are much more like their wild counterparts than dogs are. They may be tame, but thanks to their ability to live in harmony with humans while remaining independent, they've managed to retain many of the physical and genetic characteristics of their wild brethren.

[h/t Smithsonian]

Why Is Pee Yellow?

Chloe Effron
Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

Your body is kind of like a house. You bring things into your body by eating, drinking, and breathing. But just like the things we bring home to real houses, we don’t need every part of what we take in. So there are leftovers, or garbage. And if you let garbage sit around in your house or your body for too long, it gets gross and can make you sick. Your body takes out the garbage by peeing and pooping. These two things are part of your body’s excretory system (ECKS-krih-tore-eee SISS-tem), which is just a fancy way of saying “trash removal.” If your body is healthy, when you look in the toilet you should see brown poop and yellow pee.

Clear, light yellow pee is a sign that your excretory system and the rest of your body are working right. If your pee, or urine (YER-inn), is not see-through, that might mean you are sick. Dark yellow urine usually means that you aren’t drinking enough water. On the other hand, really pale or colorless pee can mean you might be drinking too much water! 

Your blood is filtered through two small organs called kidneys (KID-knees). Remember the garbage we talked about earlier? The chemicals called toxins (TOCK-sins) are like garbage in your blood. Your kidneys act like a net, catching the toxins and other leftovers and turning them into pee.

One part of your blood is called hemoglobin (HEE-moh-gloh-bin). This is what makes your blood red. Hemoglobin goes through a lot of changes as it passes through your body. When it reaches your kidneys, it turns yellow thanks to a chemical called urobilin (yer-ah-BY-lin). Urobilin is kind of like food coloring. The more water you add, the lighter it will be. That's why, if you see dark yellow pee in the toilet, it's time to ask your mom or dad for a cup of water. 

To learn more about pee, check out this article from Kids Health. 

Why Don’t We Fall Off the Earth?

Chloe Effron
Chloe Effron

WHY? is our attempt to answer all the questions every little kid asksHave a question? Send it to why@mentalfloss.com.

Do you know the saying “what goes up, must come down”? There’s a lot of truth to that. No matter how hard you hit that baseball or how high you get on the swings, you’re not going to make it into space (without a spaceship, of course). This is because of something called gravity (GRAV-it-ee). Gravity is the force that keeps you (and all your toys) from floating into space. 

The Earth’s gravity is a force that works kind of like a magnet. When you jump in the air, you come back down because gravity is pulling you towards the center of the Earth. Gravity does a lot more than just keep your feet on the ground. The strong pull of planets has created whole solar systems and galaxies. The Earth's gravity pulls in the Moon, which orbits (or circles) around it. Objects that orbit planets are called satellites (SAT-uh-lights). Some other planets have one or more moons of their own. The largest planet in our solar system, Jupiter, has 63 known moons! The Sun also has a gravitational (grav-uh-TAY-shun-ull) pull. It pulls all the planets in our solar system around it. Just like the Moon circles the Earth, the Earth circles the Sun.   

This force is something that all objects have—even you! The reason you don’t have tiny objects stuck to you is because you’re not big enough to have a strong enough pull. Even really big things like whales aren’t large enough to have a gravitational pull. Only really, really big things like stars, planets, and moons have it. 

The Moon is big enough to have its own pull. Its gravity tugs on the Earth's oceans. That's why we have ocean tides. But the Moon's gravity isn't as strong as the Earth’s. That’s why the astronauts who visited the Moon were able to jump really high. If those same astronauts went to a bigger planet, like Jupiter, the gravity would be a lot stronger. There, they would feel much heavier, and they wouldn't be able to jump much at all. People in spaceships are not near anything with a big gravitational force, so they can float in the air inside the spaceship. 

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