Cat Tales | Full Documentary | NOVA | PBS

♪ ♪ NARRATOR: They're one of the world's most popular furry pets. Who's a good kitty? NARRATOR: Famously enigmatic and totally unreadable.

MAN: We will often pretend to know what they are thinking. Are we right? (hisses) Maybe not.

NARRATOR: Now biologists and archaeologists are unraveling their secret histories. LESLIE LYONS: Behavioral genes have evolved a little bit to make a domestic cat more docile, more friendly with humans. NARRATOR: Molecular genetics is throwing new light on the cat's journey from wild animal to furry friend.

CARLOS DRISCOLL: We can really drill down and say definitively where domestic cats come from. NARRATOR: Discoveries in neuroscience are starting to explain why we find cats so appealing. (meows) It's clear that these auditory sounds are plugging straight into our emotions.

NARRATOR: Behavioral science is giving us a hint of what they think of us. LAUREN FINKA: They are able to differentiate between our different expressions. (growling) NARRATOR: And why they aren't always the ruthless predator they sometimes pretend to be.

The cat likes to hide, it likes to conceal itself. It often likes to be up high, where it feels safe. NARRATOR: What can science tell us about their future?

(meows) DRISCOLL: Humans have hybridized the domestic cat with a completely different species. (hissing) NARRATOR: We're on the prowl for "Cat Tales," right now, on "NOVA. " ♪ ♪ ♪ ♪ NARRATOR: They are as enigmatic today as when they first came in from the wild.

(hissing) Cats lead fantastic double lives. They disappear for hours, and we don't know where they go. ♪ ♪ (hissing) So, yes, cats are mysterious-- they are the best secret agents.

♪ ♪ NARRATOR: So, where do these strange house guests come from? LYONS: These were slightly larger in size, lived more in trees, but otherwise, they're going to have very similar characteristics that makes a cat a cat. NARRATOR: How did they end up living with us?

DRISCOLL: People have been speculating about it for hundreds of years. NARRATOR: And what about cat intelligence? SAMANTHA MARTIN: Cats are brilliant.

People really underestimate the brilliance of a cat. ♪ ♪ NARRATOR: Do they even like us? The right motivation for a lot of cats is not to please us.

NARRATOR: Or are they just in it for the treats? The great big motivator is going to be food. NARRATOR: What is it about these strange creatures that makes them irresistible to so many of us?

♪ ♪ ♪ ♪ ♪ ♪ Welcome to Las Vegas for the 40th TICA cat show, one of the largest feline shows in the U. S. A.

WOMAN: We have 447 cats. And we have 247 exhibitors. NARRATOR: It is a testament to our fascination with cats.

ANNOUNCER: 281 and 282. . .

Poppy is a Canadian sphinx. They're a very sweet breed. They call them Velcro kitties, 'cause they like to be on your lap all the time.

WOMAN: This is a toyger-- I invented it. He has a fantastic temperament. WAILANI SUNG: Cats are popular because they are simply very charismatic, they're independent, and they're considered easy keepers.

It's nice being able to come home, relax, have your cat come up to you, meow, sit in your lap, and purr. It just makes you feel loved and welcome. NARRATOR: There are over 70 breeds recognized by the International Cat Association.

MAN: He's a white Oriental shorthair, which is a Siamese in a designer coat. Yeah, he's a sweet boy. NARRATOR: Then there are glamour cats, like the Persian, with its thick, luxurious coat; the Maine coon, large, smart, and a deadly hunter; and the exotic, one of the most popular breeds in the U.

S. And that's just a start. SUNG: You can get small cats, you can get large cats, you can get cats with shortened legs, you can get cats with folded ears.

We estimate about one out of five households in the U. S. owns a cat.

NARRATOR: One thing is clear: owners really love their cats. Cats are perfect for me, because I just love their companionship. They jump up on your lap, and that's all I need-- just a little cup of tea and a cat.

Who's a good kitty? NARRATOR: Why are so many people obsessed with cats? The latest scientific research suggests owners literally can't help themselves.

Professor Morten Kringelbach works at the University of Oxford. He studies hedonia-- pleasure. KRINGELBACH: Pleasure is probably one of the most interesting tricks that evolution ever played on us.

It's basically making us do what it is that we need to do to survive. ♪ ♪ NARRATOR: To understand how humans experience pleasure, Kringelbach uses a magnetoencephalograph, or M. E.

G. , to map and measure electrical activity in our brains in real time. KRINGELBACH: What is really exciting about this technique is that it allows us to basically look at how the brain is thinking, how the brain is having emotions.

You can measure over milliseconds the way that the electromagnetic signals in your brain changes. And we can start to see how the brain is unfolding in real time. NARRATOR: The brain fires electrical signals between neurons.

Each tiny electric current produces a minute magnetic field. But these magnetic fields are so small, they can be swamped by interference from electronic equipment-- even from the magnetic field of the Earth. For the M.

E. G. to measure brain activity, test subjects must be locked away in a heavily shielded room.

Okay, we're just about ready to start. Just sit nice and still and just listen to the sounds. NARRATOR: In previous trials, Kringelbach's team tracked the brain's responses to the sound of a newborn baby.

(recording of baby crying playing) KRINGELBACH: So, what we're seeing here is how the signal gets into the auditory cortex, this bit here and here. It's basically just near to your ears. And you can see that after about 130 milliseconds, you get the maximal response.

Now, when you're listening to an infant crying, you also get activity in the orbitofrontal cortex, and it's happening at exactly the same time as when you are actually trying to make sense of what it is that you're hearing. NARRATOR: The orbitofrontal cortex is central to processing emotions, and the experiments suggested that the sound of a baby crying triggered a response there, before the subjects had consciously identified the sound. It seems to be an instinctive emotional reaction that may not even require rational thought.

This may be because the need to care for infants is an essential species-survival skill. It's clear that these auditory sounds are plugging straight into our emotions. NARRATOR: In tests where subjects listened to the sound of an adult crying, a much weaker response arose in the orbitofrontal cortex, suggesting only certain sounds trigger a strong emotional response.

NARRATOR: But there was another sound that produced the same reaction as a baby's cry. (recording of cat meowing playing) A cat's meow. There seems to be striking similarities between the way that we process a cat meowing and that of baby crying.

(recording of cat meowing playing) We get activity in the auditory cortices, just like we do with anything else. But before we become conscious of it, we get activity in the orbitofrontal cortex, suggesting that this is something that we need to take care of. NARRATOR: The fact that a newborn's cry and a cat's meow initiated the same emotional response could have been a coincidence-- except for one thing.

Meowing in adult cats is really interesting, because it turns out that they only really do it to humans. NARRATOR: When cats meow to us, it's as if they are hijacking our emotional responses to make us love and care for them. But are they doing it on purpose?

KRINGELBACH: It's not necessarily something that is conscious. It's just that they know that this works, just like we know that smiling at our parents worked when we were kids. (cat meows) Here, come here, you monster.

NARRATOR: They probably don't mean to manipulate us, but they do. So, we have some idea of what's going on in our heads about cats. But will we ever know what's going on in their heads?

WOMAN: I definitely think cats are more aloof than dogs. I do think they can be very emotionally distant. MAN: We will often pretend to know what they are thinking.

Are we right? Maybe not, but it's fun to imagine. ♪ ♪ NARRATOR: Cats are famously enigmatic.

So it's tough to figure out what they're feeling by looking at their faces. Happy cat. Angry cat.

Sad cat. Or is that the sad cat? We may not be able to figure out what our cats are feeling, but can science shed any light on it?

FINKA: Historically, cats aren't seen as very expressive. So there is that idea that they are particularly cold when it comes to interacting with us. NARRATOR: Compare that to a dog, whose face seems full of expression-- empathy, happiness, sadness, guilt.

Why aren't cats as communicative? FINKA: They're not really able to frown or have that sad, sort of puppy-dog-eye expression. They don't seem to have the right musculature for that.

NARRATOR: Both dogs and humans have a muscle that is responsible for raising the inner eyebrow, which we use for showing things like sadness and concern. Cats don't have this muscle. So cats are physically incapable of having faces as expressive as dogs.

However, Finka's research suggests that cats can communicate some emotion on their faces. It's just we don't speak their language. FINKA: So, we know that the muscles of the cat's face are quite different from other species, and certainly from humans.

They use the muscles in different ways, and they also have different types of muscles, and different collections of muscles will do different things. NARRATOR: Finka studies how cats' faces change when illness or injury produces pain. This is the only feeling she can currently say with confidence that a cat is experiencing.

We are looking at cats when they come into the vet's with a painful condition, and we do know that they're actually changing their expressions in relation to how they're feeling and if they're in pain. NARRATOR: She has identified a set of incredibly subtle markers to help track their feelings. FINKA: We have a series of 48 facial coordinates.

And we can actually look to see how these coordinates are altering based on what the cat's experiencing. So, whether they're in pain or not in pain, or whether they're relaxed and comfortable or perhaps fearful or frustrated. NARRATOR: Finka has identified some telltale signs, such as a cat's ears turning very slightly outwards and down; or a tiny reduction in the distance between the cheeks, mouth, and nose region.

These are all signs that the cat is not happy and in pain. But if you think this is going to usher in a new age of cat-human communication, think again. FINKA: It's very, very subtle.

So, statistically, it's significant, but in terms of the average cat owner trying to look at their cat's face, it might be a little bit more problematic. NARRATOR: Our struggle to read cats' feelings isn't going to get much easier anytime soon. But can cats read our emotions any better?

To find out, researchers conducted a series of behavioral tests. FINKA: Because it's quite difficult to test cats, we know a lot less about their cognitive abilities compared to dogs. Doesn't mean that they don't necessarily have the same level of skills and abilities.

It just means that it's much harder for us to find the right context to test them in and get them to play ball in the way that we need them to. NARRATOR: Pepper the cat has been placed in a room with her handler, who makes various faces at her. First up, scowling.

Can Pepper detect this is a negative emotion? It appears cats are less likely to react positively to someone they know if they have an angry expression. Next, a positive, smiling face.

♪ ♪ By running the test multiple times, scientists gathered results suggesting that a cat may be more likely to approach someone they recognize if they are smiling at it. FINKA: What the research suggests is that they are able to differentiate between our different expressions, and they're using this information to change the way that they are responding. NARRATOR: The limited study also suggested that cats react more strongly to both the positive and negative emotions of their owners than to those of strangers.

The behavior of owners is much more important to the cats, because we're the ones that feed the cats, and we look after them. So maybe they're more interested in paying attention to us for that reason. NARRATOR: We may struggle to read cat faces, but we're probably less inscrutable to them.

So, what led to this unlikely partnership between human and cat? To answer that, it helps to understand their origins. ♪ ♪ Domestic cats are part of a much larger and wilder family, a family with some very big footprints to fill: the lion, the tiger, the leopard-- predators at the top of their food chains.

But whatever the apparent similarity, these are not our cats' direct ancestors. All felines, or felids, evolved from the Proailurus, an animal living in Eurasia roughly 25 million years ago. These felids were probably slightly larger in size, lived more in trees than our domestic cats do.

But otherwise, it's going to have the same teeth and claws, just like a domestic cat does. So, all cats, whether you're a lion, a tiger, or a little domestic cat sitting on your lap, they're going to have very similar characteristics that makes a cat a cat. NARRATOR: DNA and fossil evidence tells us that big cats-- the lion, the tiger, the jaguar-- separated from the common ancestor around 10.

8 million years ago. Large American cats, like the lynx and bobcat, separated 7. 2 million years ago.

The domestic cat's ancestor, the most recent branch of the felid tree, established itself 3. 4 million years ago-- Felis silvestris, the wildcat. It's a much smaller subspecies of feline that relies more on surprise and stealth than brute force.

This explains the origins of some of the strange behaviors owners see in their pets. SARAH ELLIS: There are several clues in cats' behavior that they're perhaps not the apex predators, and, in fact, are prey, as well as predators. For example, the cat likes to hide, it likes to conceal itself.

It often likes to be up high, where it feels safe and where it can be very vigilant. NARRATOR: According to genetic research, Felis silvestris split into five distinct subspecies: the European wildcat, the Chinese mountain cat, the Southern and North African wildcats, and the Central Asian wildcat. But which one is the actual ancestor of our domestic cat?

DRISCOLL: People have been speculating about it for hundreds of years-- about where they came from, whether or not they came from many different species or many different subspecies of one species. NARRATOR: In 2007, geneticist Carlos Drscoll started a groundbreaking study, collecting DNA samples from wildcats and comparing their DNA to domestic cats. DRISCOLL: With the advent of molecular genetic techniques, we can really drill down and say definitively where domestic cats come from.

NARRATOR: Each subset of Felis silvestris has a distinct DNA signature made up by different combinations of the four chemical bases, A, T, C, and G. By comparing these to the domestic cat, Drscoll was able to pinpoint which subspecies was its ancestor. DRISCOLL: Domestic cats are derived from one single group of Felis silvestris in the wild, Felis silvestris lybica.

NARRATOR: Felis silvestris lybica, the North African wildcat-- a solitary animal found throughout Northern Africa and the Middle East, longer-legged than our domestic cats, with a coat that ranges from reddish to grey, to camouflage in different habitats. But when did this wildcat become our domestic companion? In 2004, on the small Mediterranean island of Cyprus, archaeologists found evidence of the earliest known encounter between cat and human.

A team lead by Jean-Denis Vigne was excavating a 9,500-year-old human settlement. During the excavation, they discovered a grave-- a grave that had two occupants: the skeletal remains of a man and a cat, a Felis silvestris lybica. VIGNE: It was amazing to find a complete animal, and especially a cat, beside a human.

And it was so early that it was really surprising to have such an evidence of connection between one cat and one human. NARRATOR: The way the bones were laid out suggested that the cat had been intentionally placed next to the man. VIGNE: They were facing each other in death, in the afterlife.

And this is a, a scene which has been arranged by people. NARRATOR: But what really caught scientists' interest was the fact that Cyprus is an island, and no trace has ever been found of native wildcats. So, how did this cat get here?

DRISCOLL: The fact that this burial was found on Cyprus means that somebody brought these cats to the island, by boat. NARRATOR: The Cyprus settlement closely matches sites found in Turkey, so archaeologists believe that's where the settlers originated, and where we know that Felis silvestris lybica was common. It suggests these people or their ancestors must have brought a cat with them.

But the Cyprus cat was different from mainland wildcats in one very significant respect. VIGNE: This cat was very big. This meant that, probably, it has been fed.

So maybe it was more or less a pet. SUNG: A larger skeleton indicates that the cat is domesticated, because he's getting enough nutrition that he can devote all that energy obtained from food into growth. NARRATOR: Cats in the wild are less able to spare the energy to grow big.

SUNG: There's a time cost to hunting. So, you would have energy diverted into fueling your hunts, then therefore, you'll be smaller. ♪ ♪ NARRATOR: On its own, the evidence of the Cyprus cat is not enough to confirm that this nine-and-a-half- thousand-year-old cat was domesticated.

But there's now evidence from genetic research that supports this theory. To date the split between wildcats and domestic cats, scientists use mitochondrial DNA. Unlike other DNA, mitochondrial material comes almost exclusively from the mother, so it's passed down the generations unaltered, except for random mutations that happen at a known rate.

LYONS: By calculating that rate of mutation, we can actually calculate the age of a specimen that we're studying. So, we use the mitochondrial clock a lot with different organisms to try to figure out their age in evolutionary time. NARRATOR: And it shows that our domestic cats split from wildcats approximately 10,000 years ago-- very close to the time of the Cyprus cat.

Why did it happen then? Well, at that moment in history, humans societies were also going through a big transformation-- becoming farmers. This started in an area of the Near East archaeologists call the Fertile Crescent.

And Turkey, where the Cyprus cat originated, was part of it. DRISCOLL: The Fertile Crescent was so rich an area for hunting and gathering that people could have little encampments that eventually grew into towns. So throughout all seasons, they could be in one spot.

NARRATOR: This new way of life relied not only on the ability to grow food, but also to store it. What's the dawn of civilization got to do with cat domestication? DRISCOLL: Humans by this point were harvesting grains and caching them, putting big stores of grains in baskets in holes in the floors of their houses.

NARRATOR: But the grain stores were an easy target for hungry wild rodents. They had the potential to devour these new food stores. Luckily for our ancestors, this new concentration of rodents attracted something else-- something wild.

Cats were likely drawn into these new human settlements because they could hear something we couldn't. Cat hearing is really just truly amazing. So, they can actually hear very low frequencies and very high frequencies.

And of course, much of their prey is squeaking at high frequencies. NARRATOR: Humans can't hear some rodent squeaks at all, as they vocalize at a frequency beyond our hearing range. But cats have ultrasonic hearing.

When we hear nothing, they hear this. (recording of high-pitched squeaking plays) The pitch of these squeaks must be lowered by 90% to make them audible to humans. Cats also have unique anatomical gifts that help them zero in on their next meal.

LYONS: The outside of their ear has an amazing amount of muscles in it, so they can turn their ear all the way around. That allows the cat to really hone in on where the mice are, rats are, where they're communicating, and hence, they're going to capture them for their meals. NARRATOR: This makes cats rodent terminators-- unstoppable killers.

The allure of easy pickings in the first human settlements-- namely, rodents-- would have been irresistible. And you'd be forgiven for thinking that cats still like to show off this prowess 10,000 years later. WOMAN: She brings us gifts.

Maybe once a month, we have a mouse appear in the house. It is a bit disgusting. We get leaves, leaves.

Oh, yeah, they brought a leaf in, and Rita brought a piece of stale toast in once from the back garden. ELLIS: So, lots of people think that their pet cats bring them gifts in the form of small rodents or birds, but actual fact, the cat doesn't believe it is a gift. The cat will often bring home the prey that it has caught because the home represents the core territory to the cat, the place that it feels safe.

NARRATOR: But 10,000 years ago, this would have been very effective PR, proving to our ancestors that cats protected valuable food resources. This was a creature you'd want to have hanging around. Maybe you set out some food for a cat to keep it around your house.

You might have done that because you thought it was eating mice and keeping your grain stores clean. ♪ ♪ NARRATOR: So, the domestic cat split around 10,000 years ago in the Near East. But how much have they changed from their wild ancestors?

DRISCOLL: The wildcat in the wild feeds only on meat. They're obligate carnivores, or hyper-carnivores. So they can only process proteins.

They're metabolically incapable of digesting carbohydrates. NARRATOR: House cats are different. While wildcats only eat meat, their domestic cousins have evolved the ability to digest some plant matter.

The domestic cat, for thousands of years now, has been living off of scraps-- not just scraps of meat, but also scraps of grains and vegetables. And the result of that is that domestic cats have a slightly longer intestinal length than their wild ancestor. And Darwin hypothesized that this is because the cats are trying to squeeze as much nutrients out of this poor food as they can.

NARRATOR: This irresistible combination of rodents and edible human refuse could explain why the wildcat decided to come in from the wild and live alongside humans. Wildcats genetically predisposed to find humans less scary would have hung around the settlements. LYONS: Anything that has to do with aggression or boldness are probably genes that are involved with the actual domestication process, because those had to change between the wild progenitor and the domestic cat in order for the cat to cohabitate with humans.

NARRATOR: Breeding between these animals would have positively selected genes that allowed them to live more closely with humans. Certainly, there have been some genes that have changed between an African wildcat and the domestic cat itself, because we know the behaviors are different. Behavioral genes, which are genes that are involved with our brain and our neurology, those are genes that have evolved a little bit to make a domestic cat more docile, more friendly with humans.

NARRATOR: Geneticists have found 13 genes that have changed in the domestic cat, compared to its wild ancestor: genes like DCC and G. R. I.

A. 1, which are associated with making cats friendlier and less afraid of people. We may never know who initiated first contact, but it's safe to assume that cats determined the terms of the relationship.

So, it's not a stretch to say that we didn't domesticate the cat, the cat domesticated itself. Genetics has confirmed that domestic cats originated in the Fertile Crescent, but it's also revealed something genuinely surprising-- one country had more influence on the genes of modern cats than any other. And it was a long way from Turkey.

Egypt. ♪ ♪ Professor Salima Ikram is an expert in all things Egyptian, including their obsession with cats. ♪ ♪ IKRAM: The ancient Egyptians really loved animals, but they also revered them.

Cats were perhaps the most popular and the most highly venerated, because of their utilitarian as well as metaphysical values. NARRATOR: In Egypt 4,000 years ago, the first images of cats start appearing-- wall carvings and paintings of cats living with humans. Egyptians especially valued the cat's killer instincts.

IKRAM: Ancient texts tell us that not only do cats kill rodents, but they also kill snakes. So, of course, the Egyptians love this, because they were much safer as a result. Imagine if you're a mother, and your child is crawling around, and then a snake approaches, and your pet cat kills it.

Also, for them, the idea that a cat was killing a snake meant that the sun god Ra was killing the evil snake Apophis. So, it was sort of doing double duty. NARRATOR: This mystic battle playing out in homes across Egypt would have done wonders for the cat's PR.

The cat became so important to Egyptians that they turned it into a goddess. ♪ ♪ IKRAM: The cult of Bastet, the cat goddess, had always been popular in Egypt, but it really came to prominence 3,000 years ago, about 500, 600 B. C.

NARRATOR: Bastet, the daughter of Ra, would often take the form of a cat. Bastet was very much about self-indulgence and beauty and love and fertility, which was very important. ♪ ♪ NARRATOR: Unfortunately for cats, being worshipped as a goddess had a very unfortunate downside.

IKRAM: We're about to go into the tomb of Raia, who was a New Kingdom official. ♪ ♪ It's a really ancient tomb, and it's not been open to the public for ages. IKRAM: Wow.

♪ ♪ Nice. IKRAM: They lived about three-and-a-half thousand years ago, just at the beginning of the time of Tutankhamen. But that's not the most interesting thing for me about this tomb.

For me, the most exciting thing is actually that it was reused to bury cats in. ♪ ♪ NARRATOR: This tomb is packed with cat mummies. The downside of being worshipped as a goddess was that it led to cat sacrifice on a huge scale.

IKRAM: Pilgrims would buy these cats to give a blood sacrifice. And so for the cat goddess Bastet, you would offer up a cat, which would then be killed. And because it was her titulary animal, it would attract her attention in the afterlife.

NARRATOR: The demand for sacrificial cats became so great, Egyptians were breeding hundreds of thousands of them. IKRAM: People were breeding these animals specifically for sacrifice. So, we think that there might have been catteries scattered all over the country, where purpose-bred cats were being given to the temples for the priests to sacrifice.

NARRATOR: This breeding program was so intensive, it may have changed the physical appearance of some cats. IKRAM: Here, this really sweet little paw, is part of the foreleg of the cat. But what's extraordinary is that you can still see some of the fur here, and it's a ginger kitty.

And a lot of the cats in paintings are ginger cats. They were favored, because they brought out the idea of the sun god Ra, and you can see this color here. NARRATOR: Seeing a ginger or orange cat today isn't unusual.

But 4,000 years ago, before the Egyptian breeding program, nearly every cat in the world looked like this tabby. The striped pattern, which is the mackerel tabby, was the original "wild-type" version of a cat's coat. The mackerel pattern helps it to have better camouflage in the environment that it has evolved in.

NARRATOR: Orange coloring isn't good for camouflage. These cats would have been less well adapted to the wild, but in the catteries of Egypt, there was no need for camouflage. LYONS: In the wild, these new coat color patterns wouldn't be tolerated.

They don't provide any advantage. But when you're around humans, they become selected by humans, because they're odd and different. It's called novelty selection.

So, when we see these odd colorations showing up in a species, that is a clear sign of domestication. NARRATOR: The orange mutation may not have occurred first in Egypt, but it was certainly established and protected here. So, if it wasn't for the Egyptians, we may not have orange cats at all.

The intensive Egyptian breeding program didn't just change the way cats looked. It changed their behavior, as well. LYONS: It's absolutely changing the cat's personality, making it more domesticated by putting these cats into large groups.

After generations of selecting for cats that go from a solitary animal to being a group species now, you're probably changing the cat's behavior to be a less stressed animal, a more bold and loving animal with humans. NARRATOR: So, Egyptians produced cats that were more attractive to humans. This could explain why the DNA of Egyptian cats makes up so much of a modern cat's DNA, compared with cats from elsewhere.

LYONS: For any given species, not all lineages are going to survive. So for the domestic cat, the Egyptian lineage of cats really dominated and was more popular, and so probably out-competed the other different lineages that were from different places of the world. (people talking in background, car horn honks in distance) NARRATOR: But how did cats bred in Egypt spread across the world?

(muezzin performing adhan over speaker in distance) ♪ ♪ NARRATOR: The same way many invading forces did at the time-- by boat. Egypt was a major trading hub in the ancient world. Precious metals, gems, and timber came in.

Grain from the fertile Nile went out. And much of that trade went by sea. IKRAM: Because the trade ships were filled with grain, primarily, there were so many rats about, that, of course, cats were really welcome, because they not only protected the grain, but they also protected the sailors from being bitten and also their own food.

So, cats were really stars on these boats. ♪ ♪ NARRATOR: Cats began traveling the known world on ships. For thousands of years, Egyptian, then Roman, then Viking ships transported cats across the world.

Vikings, in particular, seemed to have favored the unusual color mutation that had originated in Egypt. You can almost map where Vikings were by looking at the gene frequency of orange in Europe. NARRATOR: Vikings clearly couldn't get enough of their orange Egyptian cats.

DRISCOLL: It was probably true in Viking society, as it is true in most other early seafaring societies, that having a cat on board a ship was good luck. And it could be that the Vikings selected orange cats to bring on their boats for some reason that we don't know. ♪ ♪ NARRATOR: Egyptian cat genes conquered the known world.

But it seems not everyone was happy about that. Because by the Middle Ages, in Europe, cats weren't being worshipped-- they were being persecuted, mainly thanks to this man, Pope Gregory IX. This 13th-century pope produced a papal anti-cat edict.

It accused cats of being in league with Satan. And because what the pope said was the word of God, God hated cats. The solution to the satanic cat menace was simple and straightforward-- kill them all.

RONALD HUTTON: In late medieval Europe, there were festivals formed around the torturing and killing of cats. And of course, when tortured, they made, to sadists, a very satisfying amount of racket. NARRATOR: So, what was it about these relatively harmless furry creatures that was so alarming to medieval society?

HUTTON: Cats are creepy creatures to a lot of human beings. So, there's always this tension between an animal that actually shouldn't be in your home and is a predator and quite menacing, and yet is affectionate and cuddly and purry and furry and warm. NARRATOR: Another reason medieval people could have found cats disturbing was because of their serpent-like eyes.

Cats have unique adaptations in their eyes that allow them to be superb hunters at night. One of these adaptations is the reflective layer in the back of the eye called the tapetum. NARRATOR: Light entering the eye is picked up by the photoreceptors in the retina.

It hits the tapetum lucidum, reflects back, and gets picked up by the photoreceptors again. This adaptation helps give a cat six times greater night-vision acuity than a human. However, this membrane makes the cat's eyes appear to glow in the dark-- not ideal in the age of witchcraft and superstition.

We are a diurnal species. We're suited to daylight, we can't see in the dark. The night for us is disempowering, scary, and positively dangerous, whereas to a cat, it is simply a natural environment.

Isn't it, Moses? Isn't it, Moses? ♪ ♪ NARRATOR: By the end of the Middle Ages, cats had colonized almost every continent on the planet.

And they had started to diverge further and further from their Near East origins. One of the more famous and striking of these new cats was the Siamese. DRISCOLL: Siamese cats are very interesting, because they're sort of a natural breed that occurred in Thailand.

NARRATOR: The Siamese evolved in a different direction from its Egyptian ancestors, losing the tabby coloration completely, opting for something totally unique. So, this beautiful girl has got a classic Siamese coat color with the, the browner ears and nose and tail and feet, and that's the result of a thermosensitive mutation in a tyrosine gene that inhibits the production of melanin on these cats. And so, the warm parts of her body lose the color, and the cooler parts keep it.

NARRATOR: The DNA of the Siamese show they separated from the Mediterranean breeds centuries ago and evolved independently on the other side of the world. DRISCOLL: It's not believed that anybody set out to breed these cats. What happened is, is, a mutation occurred, and it stayed in this very small isolated population in Thailand.

And from there, it drifted into fixation in a certain number of cats. NARRATOR: This process is called genetic drift. It occurs when a particular mutation becomes accidentally dominant in an isolated population that doesn't mix much with the rest of the world.

If a mutation occurs in a small population, it's got a very good chance of drifting to fixation, which means that 100% of the cats in that population will then have that mutation. NARRATOR: The Siamese is an extremely unusual breed, because its looks result from a natural genetic process. Most cats in the world arose by more artificial means-- a sudden and huge expansion of cat breeding.

LYONS: During the late 1800s and into the 1900s and on, cats have become a status symbol. Europeans realized that there were different variety of cats from all around the world. They then incorporated that into their breeding programs.

People started selecting cats because they had unique varieties. The Angora cat came from the Near East; the Abyssinian came from Ethiopia; the Manx cat, which had no tail, came from the Isle of Man. NARRATOR: And this new trend of cat breeding was enthusiastically taken up in the U.

S. in short order. LYONS: One of the first is the Maine coon, the natural long-hair cat that really actually came over with the Pilgrims, but now was indigenous to the United States.

Another very interesting cat breed that developed in the United States is the ragdoll. This cat developed from cats that were in California. NARRATOR: Breeding, both natural and human-assisted, has given cat owners an astonishing level of choice.

So, you might think, that after 10,000 years and all this effort, we've bred out their wild side. (hissing) Apparently not. These are feral cats.

They are not wild animals, despite how it may look. These cats, or their close relatives, were once normal house pets. Take a domestic cat out of the home, and they can turn a lot less loving.

Feral cats typically will start up with fight-or-flight when people come into play. (growling) NARRATOR: This suggests all domestic cats have this wildness within them. So why don't they all turn feral?

The socialization window for cats is very important. If you want a friendly cat, a cat that is accepting of people and new experiences, this is usually between two to seven or eight weeks of age. If they miss that window, it's more likely to have a cat that's more fearful and more what we consider feral.

NARRATOR: U. S. cities like Atlanta have a serious problem with feral cats.

SUNG: We don't want to euthanize a cat, because you know what happens when you remove cats from the outdoor environment? Is that new cats come in. So, we actually maintain a stable population so we don't add more cats into that area.

NARRATOR: So, veterinarians like Dr Ashley Randall work on programs to try and control the situation. RANDALL: Neutering and spaying is really, really important when it comes to feral populations, especially if we're trying to control the numbers. Any time a population gets really, really high, you run the risk for disease, and that's for people and for pets.

♪ ♪ NARRATOR: Helping Dr Randall with Atlanta's feral-cat problem are Lizzy and Kasia from the Pets for Life Program. LIZZY TRAWICK: We are out today doing some cat-trapping for what's called TNR-- trap, neuter, release. KASIA JAKUBOWSKI: A female cat will have kittens every two months, and she will be impregnable right after she delivers.

So, pretty much, you can assume that every female cat in the wild out here is pregnant at all times. NARRATOR: Lizzy and Kasia are tracking a feral cat active in the area. So they've left a series of traps filled with food.

Well, it looks like somebody's in there. Yeah. Hi, there.

Let's see what we've got. Hi. Looks like the right one.

We're going to take you to the vet. Let's get him in the van. Okay.

NARRATOR: On average, they catch 15 cats a week. It's okay, buddy. NARRATOR: Each receives a welcome health check, vaccinations, and neutering or spaying.

RANDALL: Okay, so, his heart sounds good. And his gums are nice and pink. Very good, big guy.

All right, so we are going to put him on his side, and then we are going to give him his sedative. ♪ ♪ All right. RANDALL: All we're doing is taking away the reproductive organs, so we're taking away organs that they can live without very easily.

For males, they're up within about 20 minutes of that procedure. So he is going to go back outside and live out his life. All righty, big boy.

NARRATOR: The whole procedure takes less than ten minutes. And a few hours later, the cat is released back onto the streets. TRAWICK: It's okay, buddy, we're home.

SUNG: The reason that we trap, neuter, and return feral cats-- versus keeping them and adopting them out-- is, they're truly not happy to live inside with people. TRAWICK: This way. TRAWICK: The vet said he was pretty healthy, surgery went well.

So he might be a little drowsy this evening, and then he'll be back to full energy tomorrow, ready to take on the world. There you go. NARRATOR: So, domestication may only be skin-deep, and cats are essentially still wild animals-- wild animals that now live with us.

This essential wildness may explain in part why cats are not trainable in the way dogs are. Dogs want to please their owners; they are what is known as hyper-social. Cats don't really care what their owners want.

SUNG: It's a lot more difficult to train a cat compared to a dog because dogs were specifically selected for their trainability, whereas cats have shorter attention spans, and people also really don't spend a lot of time training cats. NARRATOR: But just because they aren't as cooperative as dogs doesn't mean they aren't as smart or trainable. You just have to make it worth their while.

Meet Samantha Martin. MARTIN: This is Meowy Manor. ♪ ♪ NARRATOR: Samantha is the manager of a traveling troupe-- or, more accurately, pride-- of performing cats.

Most of the training happens in here. ♪ ♪ MARTIN: Cats are brilliant. People really underestimate the brilliance of a cat.

By training them, they get to use their brain. They have to figure out what it is that I want from them. ♪ ♪ NARRATOR: To train her cats, Samantha uses a method called operant conditioning, also known as clicker training.

This is the target stick, so he was trained to jump up to wherever I pointed the target stick. And once he had all four paws up on the barrel, I'd just click and treat. The clicker acts as a bridge or a marker to let the cat know that they'd just done a behavior that's going to give them a reward.

Got it, you got it. (clicks) MARTIN: Once the behavior's learned, I no longer need the target stick or the clicker, just the prop itself. And they know what to do with the prop.

♪ ♪ So, that's the finished trick. ♪ ♪ NARRATOR: The question is, are the cats training to please their owner, or are they just there for the food? SUNG: If you want to train a cat, the great big motivator is going to be food.

Food is a primary reinforcer. It's something that they can't live without. So, most cats can be trained to work for that food.

NARRATOR: Compared to dogs, there hasn't been much research into cat cognition and intelligence. But cats are clearly clever-- when they choose to be. (music playing on speakers, crowd applauding) The Acro-Cats play to full houses as they tour the U.

S. A. -- audiences crammed with envious cat owners wondering why their pet won't do this.

Experience and hard work says, "Reward with food, and you might have a little more luck. " ♪ ♪ So, where next for our wild feline friends? Well, some people have plans to completely reinvent the cat.

DRISCOLL: All domestic cats up until the last 20 years have been purely Felis silvestris. Humans have, very interestingly, now hybridized the domestic cat with a completely different species. NARRATOR: Anthony Hutcherson has been breeding one such hybrid.

. . Come on, buddy.

NARRATOR: The Bengal cat. HUTCHERSON: Bengals come from a cross between domestic cats and a wildcat species called the Asian leopard cat. Personality-wise, they are a little different from other cats, and they're pretty active and interested and intelligent.

So, if you just want a cat to sit on your lap, this is not the cat for you. (chuckles) ♪ ♪ LYONS: The difference between a domestic cat and an Asian leopard cat is about six million years of evolutionary time. That's on the same range as the difference between a human and a chimpanzee.

ANNOUNCER (on P. A. ): Bengal adults, 207 through 216.

NARRATOR: With such a huge evolutionary difference, can these new hybrid cats still share our homes? HUTCHERSON: Come on, buddy. HUTCHERSON: The challenge lies in getting those physical traits that attract your eye and have excited humanity since the beginning of time without those traits you don't want on the inside: getting scared easily, peeing in the corners, you know, needing to eat a lot of raw, bloody meat.

NARRATOR: The Bengal is not the only exotic breed trying to inject a wild look into cats. The Chausie is a cross between a domestic cat and another non-Felis silvestris, the jungle cat. And the savannah is a cross between a domestic cat and a serval, a cat that broke away from the wildcat's line over eight-and-a-half million years ago.

I think these cats are both the future and the past of domestic cats. They represent the thing that people love and want as a bit of the wild in their house, which is kind of the oldest reason people love cats anyway. NARRATOR: 10,000 years ago, our first feline furry house guests moved in.

Since then, they've traveled the world, been feared by popes, and worshipped like gods. They've hijacked human instincts for their benefit, apparently learned to read human emotions, but kept their own feelings under wraps. They can even entertain us-- as long as we make it worth their while.

And though they've gone through subtle genetic changes, their wild nature has endured despite our best efforts. (cat shrieks) What's more, they've leveraged some of those traits to become the ultimate consumer pet, bringing a little bit of the wild into millions of homes. And what do cats make of all this?

As usual, they're not saying. ♪ ♪ ♪ ♪ To order this program on DVD, visit ShopPBS or call 1-800-PLAY-PBS. Episodes of "NOVA" are available with Passport.

"NOVA" is also available on Amazon Prime Video.