MinuteEarth Explains: Cats vs Dogs
Hi, I'm Emily from MinuteEarth. And this is my cat Yardly. Or, as we've called him since he lost that eye, YARRRdly. Coming up, four short stories about the science of our feline overlords and canine underlings. First up, it turns out that somewhere in the process of domestication, we might have given our pets a small lobotomy. Domestication has puppified dogs, fluffified sheep, and spotified horses. But there's a less obvious physical change that virtually all domesticated animals share: shrunken brains. Duck brains have shrunk by about 15%, cats brain by 30%, and pig brains by a whopping 35%. We've even found smaller brains in farmed trout, which is weird because, in general, the size of animals' brains and the size of their bodies is super tightly linked. Mites have smaller brains than ants, which have smaller brains than mice, which have smaller brains than elephants, and so on. The same relationship exists for individuals within species.
So, for example, small wolves have smaller brains than big wolves, and small dogs have smaller brains than big dogs. But when you compare wolves and dogs, between individuals of the same size, the wolves have bigger brains. No matter what body size is. What's more, across different domesticated animals, a disproportionate amount of the shrinkage happened in parts of the brain that monitor information from the outside world and tell animals when and how to freak out.
Sort of like the brain's panic button. We know that in general, animals with bigger panic buttons have a more sensitive fight-or-flight response, and animals with smaller panic buttons are naturally tamer. So, those are the ones we probably would have tried to domesticate. And by breeding the tamest animals with each other, we shrunk their panic buttons, and therefore their brains, even further. In short, domesticated animals have formed long-term partnerships with humanity, by literally losing their minds. All of our pets are tame. But some pets are tamer than others, and cats… well, do cats even like us? How did we end up sharing our houses with them? Let alone shelling out for expensive eye removal surgeries? This next video explains. Hi, I'm Joe from It's Okay To Be Smart. If you line up the world population of domestic cats, that kitty conga line would wrap nearly six times around the planet! Meow-adays, there's around 85 million pet cats in the US alone. How did cats become the grumpy, laser-chasing, keyboard enthusiasts we know today? And what role did humans play in their trans-fur-mation? It all started around 11 million years ago in Asia, with a cat that looked something like this.
We think this ancestor of modern cats travelled far and wide in search of food and mates, an instinct shared across the feline family. Single pumas have been known to patrol nearly 1000 km². That's as big an area as 200,000 American football fields. That urge to roam drove early cats over land bridges into new worlds, and species diverged, many of which we'd recognize today. It was the smaller wildcats, at least the ones that survived big upheavals like a changing climate and the onslaught of a certain pesky primate that eventually became our first feline friends. As we moved away from hunter-gatherer ways and put down roots, food piled up and this brought other animals like rodents to the table. And cats came strolling in after them. Don't let those big eyes fool you. Felines are murder machines. They're more successful hunters than almost any other predator. And those hunting instincts would have been a big help to our ancestors. Cats that ate rodents but didn't eat children got to stick around. People began getting attached to cats. In fact, a child and cat were buried together in a 9500-year-old grave in Cyprus. Cats weren't quite getting attached to humans, though.
They retained their urge to roam, and their killer instinct, and still pretty much looked like their wild cousins. But they were changing. Housecats can digest plant matter better than wildcats, helping them make meals of human scraps. What's more, recent changes in genes influencing how cats respond to fear make domestic kitties friendlier than wildcats, even if we still can't exactly train them. The ancient Egyptians worshipped cats as incarnations of a goddess, and many of us take a hieroglyph from their tablet today. Cats may have even learned to demand our attention. In the wild, all kittens meow to mom, but once she stops listening, they move on to other sounds. But housecats never leave their adoring mothers, so the kitten call continues.
So how did ferocious felines become purr-fect pets for millions of us around the world? It all started with the cat who ate the rat who ate the grain that lay in the hut that our ancestors built. Most cats still look pretty similiar to their undomesticated ancestors. But dogs… well, these guys don't exactly look like cousins. But how similar are modern dogs to one another? Ever since rich British folks invented dog shows as a spectator sport in the late 1800's, people have been parading pooches around with the goal of taking the top spot in their dog's so-called "breed group".
These breed groups are based on the historical jobs dogs were bred to do. With game retrievers like labs and spaniels in the sporting group, guard dogs like Dobermanns and mastiffs in the working group, and herding dogs like collies and sheepdogs in, well, the herding group. And although most dogs today are just butt-sniffing layabouts, their breed group still influences how we think about them, which is why dog breed organizations describe dogs in the sporting group as attentive, dogs in the herding group as smart, and dogs in the working group as courageous. But perhaps unsuited for families with young kids. However, two decades of canine research have revealed that, while dogs in a given breed group often share certain skills, they don't really have that much else in common. In one study in Sweden, researchers ran more than 13,000 dogs of 31 different breeds through a course full of sounds, surprises, and random humans attempting to snuggle.
They found that levels of playfulness, curiosity, sociability, and aggression did not differ among breed groups. Even weirder, it turned out that golden retrievers are more similar to Rottweilers than they are to their fellow sporting dogs. And boxers are more like labs than they are like other working dogs. In fact, most dogs act more like breeds outside their group than they act like other breeds within their group. What's more, dozens of canine intelligence studies have shown that, when it comes to solving mazes and following commands, all breed groups perform about the same, even though some individual dogs are definitely smarter than others. So have dog enthusiasts somehow been imagining all of these differences among breed groups? Maybe! Psychology research suggests that once we begin to see something in a particular way, we naturally seek out evidence that strengthens that image, and ignore evidence that undermines it.
But the truth is that you can't judge a bark by its cover. I'm sorry about that last pun. We aim for groan-worthy, but that last one was re-pug-nant. Anyway, last up, we've got a video for you about how your dog can protect you before you're born. Mmm, puppies. Most dog owners say companionship is the number 1 reason to have a cuddly, devoted tail-wagger. And some people also have dogs for assistance or protection. And just look at them! They're so cute! So it's not surprising that we're willing to put up with less savory features of dogs, like muddy pawprints, and slobber all over everything. Yet slobber and other pet dirt my actually be a pet benefit too. Especially if you happen to be an unborn baby. Dogs, and also cats, influence the microbial communities in our homes so much that if your mother lives with a cat or dog while she's pregnant with you, you're about 30% less likely to suffer from allergies as a child. This sounds kind of crazy, and we don't know exactly why it happens, but the most likely explanation is called the hygiene hypothesis.
You know how children from Amish farm families have been found to suffer less from allergies and asthma than is typical in the modern Westernized world? Well, scientists think it's because their immune systems develop more fully, thanks to exposure to a wide variety of dirt, bacteria, and germs in fermenting feed, cow manure, and other barnyard delights. A key part of your immune system is the cells that recognize and neutralize foreign bacteria, viruses, transplanted body parts, or even your own damaged cells. Healthy cells in your body have distinctive proteins on them that immune cells recognize as part of you, while intruders and unhealthy cells without "you" proteins are flagged for careful monitoring.
If any "not you" stuff starts causing too much harm, your immune cells will attack it and take note to act quickly and vigorously against it in the future. Basically, learning who's harmlessly passing through, and who's a dangerous intruder. But if the immune system incorrectly identifies an intruder, or doesn't properly learn who's who in the first place, our bodies can overreact to harmless substances, like a life-threatening allergic reaction to a minor bee sting.
In the Western world, the percentage of children who suffer from immune system overreactions like allergies and asthma has roughly doubled in the past forty years or so, even as infectious diseases have become much less common, thanks to improved hygiene, water, and sewage treatment, and so on. It's highly likely that the increased prevalence of allergies and asthma is due in part to the fact that the environments we live in are too clean, and don't give our immune system proper opportunity to learn who's who at a young age. Kind of like how we're better at learning foreign languages when we're younger, our immune systems are best at learning to distinguish harmless foreign substances from harmful ones when exposed to them very early in life.
That's why having dog slobber, kitty hairballs, and muddy pawprints around your mother while you're in utero might get your immune system off to a proper start even before you're born. We still don't know exactly how your mother's exposure to extra bacteria influences you in the womb, but we do know that having a pet around before and after your birth may help keep your immune cells from barking up the wrong tree. That's a bark pun I'm willing to stand behind! Which is great. I'd hate to go out on a RUFF note. Thanks for watching!.
