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]

This 'Time-Traveling Illusion' Is Designed to Trick Your Brain

A team of researchers from the California Institute of Technology (Caltech) have designed an illusion that might trick your brain into seeing things that aren’t there, the New Atlas reports.

Dubbed the Illusory Rabbit, it provides instructions that are simple enough to follow. Start playing the YouTube video below and look at the cross in the middle of the screen while also watching for flashes that appear at the bottom of the screen. Most importantly, you’ll want to add up the number of flashes you see throughout the video. (And make sure your volume is up.)

We don’t want to spoil the fun, so before we explain the science of how it works, check out the video and try it for yourself.

Did you see three flashes paired with three beeps? You’re not alone. This is due to a phenomenon called postdiction, which is a little like the opposite of prediction. According to a paper outlining these findings in the journal PLOS ONE, postdiction occurs when the brain processes information retroactively [PDF]. This occurs in such a way that our perception of earlier events is altered by stimuli that come later. In this case, you might think you missed the flash paired with the second of the three beeps, so your mind goes back and tries to make sense of the missing information. That's why you may see an “illusory flash” in the middle of the screen, sandwiched between the two real flashes.

For this reason, the researchers call the mind trick a “time-traveling illusion across multiple senses” (in this case, vision and hearing). It’s successful because the beeps and flashes occur so rapidly—in less than one-fifth of a second. The senses essentially get confused, and the brain tries to fill in the gaps retroactively.

"Illusions are a really interesting window into the brain," the paper’s first author, Noelle Stiles, said in a statement. "By investigating illusions, we can study the brain's decision-making process.” Researchers wanted to find out how the brain “determines reality” when a couple of your senses (in this case, sight and hearing) are bombarded with noisy and conflicting information. When the brain isn’t sure of what’s going on, it essentially makes up information.

“The brain uses assumptions about the environment to solve this problem,” Stiles said. “When these assumptions happen to be wrong, illusions can occur as the brain tries to make the best sense of a confusing situation. We can use these illusions to unveil the underlying inferences that the brain makes."

[h/t New Atlas]

How Did 6 Feet Become the Standard Grave Depth?

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It all started with the plague: The origins of “six feet under” come from a 1665 outbreak in England. As the disease swept the country, the mayor of London literally laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Mayor and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”

The law eventually fell out of favor both in England and its colonies. Modern American burial laws vary from state to state, though many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything). Given an 18-inch dirt buffer and the height of the average casket (which appears to be approximately 30 inches), a grave as shallow as four feet would be fine.

A typical modern burial involves a body pumped full of chemical preservatives sealed inside a sturdy metal casket, which is itself sealed inside a steel or cement burial vault. It’s less of a hospitable environment for microbes than the grave used to be. For untypical burials, though—where the body isn’t embalmed, a vault isn’t used, or the casket is wood instead of metal or is foregone entirely—even these less strict burial standards provide a measure of safety and comfort. Without any protection, and subjected to a few years of soil erosion, the bones of the dearly departed could inconveniently and unexpectedly surface or get too close to the living, scaring people and acting as disease vectors. The minimum depth helps keep the dead down where they belong.

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

This article originally appeared in 2012.

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