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What Animals Can Teach Us About Being Human

Barbara Natterson-Horowitz and Kathryn Bowers

The call from the head vet at Los Angeles zoo was as unusual as it was urgent: "Barbara? We've got an emperor tamarin in heart failure. Any chance you could come out today?" Barbara Natterson-Horowitz, a cardiologist at the University of California medical centre -a leading heart transplant hospital - grabbed her car keys and set off across town.

Ever since her children had been to a sleepover at the 113-acre zoo, Natterson had been helping out with advice on some of its trickier cases. Heart failure in a tamarin monkey was something she hadn't seen before and her own heart did a little flip when a veterinary assistant walked in carrying a bundle wrapped in a pink blanket.

Spitzbuben the tamarin was a small, furry female with huge brown eyes and a wispy, white moustache. It "pushed every maternal button" she had.

As Natterson prepared to scan the creature's heart, she did what she would normally do when examining a child, murmuring reassuring words while looking deeply into its eyes. As Spitzbuben solemnly stared back, a vet tapped Natterson on the shoulder and said abruptly: "Please stop making eye contact; you'll give her capture myopathy." To the monkey, Natterson's steady gaze wasn't saying: "Don't be afraid, I'm here to help you." It was saying: "I'm starving, you look delicious, I'm going to eat you." If the animal became very frightened, that could trigger catastrophic heart failure.

Natterson was puzzled; after 20 years of medical practice she knew myopathy was a disease affecting heart muscle, but capture myopathy she had never heard of. Later that evening, she looked it up. "It was one of those accidental 'aha' moments," she says.

What she discovered was the "enormous similarity" between human and animal illness - a revelation of the astonishing ways that animals can teach us about the human condition. Her chance breakthrough transformed her life and is now revealed in an amazing new book.

At the time, about seven years ago, the (human) cardiac world was abuzz with talk of takotsubo syndrome, a condition discovered by Japanese doctors that proved what had until then seemed to be no more than a fanciful idea: that people could die of a broken heart. Cardiologists frequently treated - and were baffled by - patients who had suffered heart failure following a severe emotional shock but showed none of the usual signs of heart trouble: no clogged arteries, no blockages and no blood clots. The Japanese doctors had noticed that emotional stress could cause a part of the left ventricle of the heart to balloon out, disrupting its contractions.

"As I looked at capture myopathy it really resonated with this broken heart syndrome," Natterson says.

"I put the human phenomenon side by side with the animal one: 'emotional trigger ... surge of stress hormones ... failing heart muscle ... possible death'. I was intrigued by how close some aspects were. But what was more startling to me was that takotsubo was being trumpeted as this fantastic newly identified syndrome among cardiologists - yet veterinarians had known about it for decades."

She began to wonder what else vets knew that doctors didn't: "It became a kind of hobby: if I saw a disease in a human, I looked for an animal correlation. I started asking, 'Do animals get breast cancer or melanoma? Do animals get brain tumours? Do they get syphilis or erectile dysfunction? Do animals faint?' And the answer was, 'Yes, yes, yes, they do'."

Natterson found that jaguars get breast cancer and may carry the same genetic mutation that causes the disease in some women. Rhinos in zoos get leukaemia. Western lowland gorillas are prone to dying of a ruptured aorta, the thing that killed Albert Einstein. Animals also get the clap: koalas in Australia are stricken by an epidemic of the sexually transmitted disease chlamydia.

I wanted to know whether animals self-harm or commit suicide or have eating disorders "I had trained as a psychiatrist before I became a cardiologist and I was sceptical as to whether a psychiatric correlation would hold out," Natterson says. "But I did the same kind of research and it did. I looked at whether animals got OCD [obsessive compulsive disorder] or suffered separation anxiety. I wanted to know whether animals self-harm or commit suicide or have eating disorders or whether they ever get high and, again, the answer was yes - to everything. It really shook up the way I thought about human disease." Last year, based on the knowledge she had gained about the overlap of human and animal disease, Natterson set up a one-day symposium bringing together 200 experts from UCLA, the University of California Davis School of Veterinary Medicine and Los Angeles zoo.

The gathering discussed skin cancer in a rhinoceros, diabetes in monkeys, hypothyroidism in a lynx and a dissecting aneurysm in a beluga whale. She has since helped to create 10 teams made up of doctors and students from UCLA's medical school and its veterinary counterpart at Davis to look at a number of shared human/animal diseases.

"I had a dog and a few pets as a child and a strong interest in wildlife and evolutionary psychology but I had no idea that we shared so many diseases with animals, and I think many of my physician colleagues have been surprised too," Natterson says.

"You have these two highly siloed fields of veterinary medicine and human medicine and we can learn from each other but we have very few points of professional collaboration. Vets and physicians rarely speak to each other. Doctors can be snobs about 'animal docs' and vets have a kind of joke that medical doctors are veterinarians who only know how to treat one species."

Natterson has come up with a name for the quest to extend medical knowledge through research into the human and animal world - zoobiquity - which is also the title of the book she has written with the American science writer Kathryn Bowers. It examines the fascinating ways in which human and animal behaviour and illnesses reflect one another.

When Natterson took her 12-year-old daughter to have her ears pierced, for instance, the girl passed out as the needle approached. It set Natterson wondering why on earth that would happen, given that her daughter wanted to be there - she had been begging to have her ears pierced for months - and was under no threat.

But a look at the animal kingdom suggested that an unconscious bid for survival lay behind the fainting fit. Fainting seems to be connected to the fight-or-flight response, which Natterson believes should more properly be fight, flight or faint. Animals in danger frequently faint. Rather than their heart beating faster at the prospect of danger, the heart rate plummets and their blood pressure drops. They faint, effectively avoiding danger by playing dead, much as a soldier who has been knocked unconscious on the battlefield might survive because the enemy believes him dead.

Animals that faint frequently lose bladder control and the smell of urine may also help to repel a would-be predator. Even some fish faint when enemies are near. Predators such as sharks, rays and catfish have heartbeat detectors that track down prey by the sonar waves their bodies generate. The slowing of the heart rate caused by fainting makes a vulnerable fish acoustically invisible - and therefore safe.

The fainting response may also play a part in explaining cot death. When Canadian scientists played recordings of wolf howls to fawns - left alone in the woods while their mothers went off to forage - their heart rates dropped dramatically, as a slowed heart rate stopped them from rustling around and attracting attention.

The same sound/shock mechanism was found by accident in human babies during the first Gulf war in 1991 when Iraqi Scud missiles were hitting Tel Aviv. Three women were in a labour ward strapped up to monitors. At 3am there was a terrifying shriek of the Scud alert siren. As the staff scrambled to put on their gas masks they noticed that the heart rates of all three babies had plummeted.

Other research showed that animals who are trapped or restrained tend not merely to faint; the heart sometimes slows so dramatically that they die. Could it be that the same mechanism might be set off in a baby, swaddled and lying face down, if a car alarm sounds in the middle of the night?

"It's something we want to be very cautious about," Natterson says. "There are many theories about cot death; we just thought we could add one additional voice to that discussion by pointing out this animal autonomic reflex and the response to restraint."

"The slowing of the heart rate of the babies in Tel Aviv shows this reflex is real and that it is common across species spanning groups. It's another way of bringing that animal information into the human discourse."

Cancer, of course, is the disease most feared by humans and Natterson found that it frequently affects the animal kingdom too, and has done for millions of years. Paleontologists examining the fossilised remains of a gorgosaurus, a meat-eater and relative of tyrannosaurus rex, found a mass in the dinosaur’s skull that some believe to have been a brain tumour.

Ancient Egyptian doctors described human breasts with 'bulging tumours' and Greek doctors, including Hippocrates, wrote of cancers, using the term karkinos. Today, we think of cancers being caused by carcinogens related to toxic chemicals or other features of our modern world but research seems to suggest that cancer has not only existed for millions of years but is rampant throughout the animal kingdom. Wild sea turtles are dying in large numbers from cancerous tumours probably caused by a virus; horses — particularly greys — are susceptible to skin cancer, and cancer has been found in creatures as small as fruit flies and cockroaches.

Research into melanoma — an aggressive form of skin cancer — in dogs is already advancing treatment for human patients. Doctors at the Memorial Sloan-Kettering hospital in New York, one of America’s leading cancer research hospitals, tracked the progress of 350 dogs (all family pets, including a siberian husky, a german shepherd and two cocker spaniels) that had been diagnosed with various stages of melanoma. As a last-chance experimental treatment they were injected with a type of human DNA believed to boost immune systems. More than half exceeded their life expectancy. That led to a vaccine against melanoma now routinely used by vets and has led to work on a similar vaccine to prevent melanoma in humans. There's this idea that with proper habits we could obliterate disease but disease is part of life.

Natterson frequently treats patients with heart problems as a by-product of cancer and says that such research not only gives them hope; the idea that cancer is common throughout the animal kingdom also lessens irrational feelings of distress and guilt.

"There's a tendency to think we caused our own diseases," she says. "We believe we suffer diseases of civilisation and, of course, we do - I'm a cardiologist, I've taken care of people who have eaten, drunk and smoked their way to heart surgery. But what we do is amplify our risk of disease by our bad habits. If we stripped away all our bad habits, we would still have disease, and that thought comes as a relief to many people. There's this idea that with proper habits we could obliterate disease but disease is part of life. And, indeed, a disease like cancer is a good example of that because it is caused by mutation ... the mutation we need to create evolution through natural selection."

Drug abuse, eating disorders and self-harm we also think of as diseases of modern society but they, too, have parallels in the wild that might help us to understand and treat them better.

Do animals get high? Yes, they take every chance they get. Wallabies living near a farm in Tasmania that grows opium for medical purposes are pretty much permanently stoned. A flock of 80 cedar waxwing birds in southern California crashed into a glass wall, drunk on Brazilian pepper tree berries. A pet cocker spaniel in Texas perplexed her owners with her constant toad licking; it turned out the skin of the cane toads in the garden gave out a hallucinogenic toxin. The dog licked the toads so often and so enthusiastically she sucked the pigment out of their skin.

"I was blown away to discover substance abuse in the wild," Natterson says. "I have a couple of friends who have struggled with substance abuse, one a recovering heroin addict, and she really resonated with the idea that there's this neurobiology that connects to her addiction. She felt she and others that struggle with substance use could find some comfort in understanding their urges and find some perspective."

The difference between animals and humans, of course, is that humans are supposed to understand the damage they are doing themselves by shooting up heroin or snorting coke. But Natterson’s research has convinced her that when addicts feel compelled to take drugs they are driven by a deep, primal force that convinces them they are doing something good.

In the wild, behaviour that enhances survival - preening, cleaning, finding food, winning a fight with a rival - is rewarded by a flood of chemicals to the brain, a 'natural high'. In humans and animals who encounter drugs, that high is achieved without the good behaviour that should prompt it.

"Behaviours that are fitness- enhancing are rewarded by a good neurological experience. What drugs do is get in and hijack that," she says. "If you look at the most common behavioural addictions - gambling, sex or food addiction - they are connected to behaviour that enhances survival. Even a BlackBerry addiction connects to the need for information, which in social animals is great and something that will be rewarded. So it expands our perspective to see that these diseases are not uniquely human. They only feel uniquely human because only humans have a BlackBerry."

Similarly, self-harm seems a peculiarly modern, 'urban' disorder. As a young psychiatrist, Natterson treated a number of “cutters”, a surprisingly common phenomenon - the actress Angelina Jolie has admitted cutting herself in times of crisis, as did Princess Diana - and was struck that the young women she talked to always seemed to say the same thing: that after they had sliced through their skin they felt a sense of relief rather than pain.

A psychiatrist's reaction to such behaviour, she says, would normally be to look for signs of childhood trauma or sexual abuse. But it makes more sense if you look to the natural world and see self-harm as a kind of grooming gone too far. As a fitness and survival-enhancing behaviour, preening and cleaning is also rewarded with a natural high, but in some creatures that high seems to become an addiction. Birds frequently suffer pecking disorders in which they strip themselves of feathers. Dogs such as labradors, golden retrievers and dobermans will obsessively lick and gnaw at their bodies, creating a condition known as acral lick dermatitis. Horses will bite their own flanks until they draw blood.

"This was a very new perspective for me and I came towards it sceptically," Natterson says. "When I was training as a psychiatrist no one ever suggested behaviour might have an evolutionary basis. But looking at animals who self-harm, at the kernel of the self-harming behaviour is a grooming behaviour: picking, licking, preening."

She recalled working with patients who said that cutting brought relief. This "was a very intriguing and counterintuitive thing it was hard for me to get my head around. But if you frame cutting as grooming gone wild you can see it as an amplification of the kind of self-grooming, tactile behaviour you see in some animals."

In September, Natterson will be hosting a zoobiquity conference, bringing together experts from the medical and veterinary worlds, to foster “greater understanding of our shared biology”. They will discuss a number of conditions, including infertility (through a comparison between methods used to breed endangered species in a zoo with the treatment of a 31-year-old woman), breast cancer, obesity and bullying (looking at the mechanisms by which stronger creatures select weaker ones to dominate). The aim is to improve treatment for creatures of every kind.

"As physicians, we're just leaving knowledge on the table if we're not looking at the animal experience," Natterson says. "We're talking about research into naturally occurring disease in what must be trillions of mammals with four-chambered hearts that look like ours and immune systems that are very similar."

"When I was coming up through my education I was taught with a wagging finger,"'Don't anthropomorphise, that's not scientific" Well, it turns out we now know through the human genome project that we share the vast majority of our genome with chimpanzees. We now have an opportunity and we have science behind us in a way we really didn't have a couple of decades ago. We're in a position to move beyond reprimanding ourselves for projecting onto animals and taking a more scientific approach to what the observed similarities between us might mean."

In other words, we have the opportunity to advance knowledge using naturally occurring diseases that have so far - much like an animal in camouflage - been hiding in plain sight.

More books on Animals

'What do you call a veterinarian who can only take care of one species?'

An M.D.

It's a longstanding joke that veterinarians make about doctors, said UCLA cardiologist Barbara Natterson-Horowitz, at an event co-presented by UCLA at the Petersen Automotive Museum. And it's a joke with bite. It shouldn't be news that humans are animals too, but sometimes it seems that way to doctors who treat humans.

Natterson-Horowitz–by collaborating with veterinarians, evolutionary biologists, and even wildlife conservationists–is challenging the divide that has long separated human medicine from animal medicine. She and UCLA writing lecturer Kathryn Bowers, authors of the new book Zoobiquity: What Animals Can Teach Us About the Art and Science of Healing, spoke with Los Angeles Times science writer Eryn Brown about the parallels between human and animal diseases, and how all species stand to gain from recognizing where we overlap.

Natterson-Horowitz first became interested in the connections between animal and human health when she was called in to do ultrasounds for animal patients at the Los Angeles Zoo. She began listening to the veterinarians as they spoke during their rounds, and soon noticed more and more animal diseases she'd seen in humans.

"We take our pets to the veterinarian for this problem or that problem," said Natterson-Horowitz. "It hadn't dawned on me that there were these parallels. On the one hand it's obvious,” because we share so much of our genes with chimpanzees, for instance.

Bowers and Natterson-Horowitz investigated which human diseases had animal counterparts. The first big overlap came in cancer, which affects species including llamas, kangaroos, and big cats. We think of breast cancer as a human illness - but, said Bowers, being a mammal means you have breasts, and if you have breasts you can get breast cancer. Jaguars in zoos have a high incidence of breast cancer, which may be related to the BRCA1 gene mutation. (This mutation is often found in Jewish women, and Natterson-Horowitz said that this book chapter had originally been titled 'Jews and Jaguars.') Dairy cows and goats - two animals whose job is primarily to nurse their young - have a low incidence of breast cancer, while studies of humans have shown that women who nurse are at a lower risk for breast cancer.

Are there any diseases, asked Brown, that have turned out to be a dead end in searching for an animal corollary?

The Zoobiquity team's answer: Epicardial coronary disease is the biggest cause of heart attacks in humans, but because it's a disease of civilization amplified by our lifestyle and diets, it’s not found in most animals. Animals do have other forms of heart failure, however - including the kind of heart disease that can cause high school athletes to drop dead, which is also found in cats.

The parallels extend to psychiatric diseases. Bowers was surprised to find out that self-injury occurs in animals. "To me that seemed so very, very human, that you would even injure yourself," she said - it seemed to her to require a sense of self. Yet "animals when they're under stress will do all sorts of things to make themselves feel better, including turning their own teeth or talons on themselves."

Horses flank bite or birds peck at themselves until they bleed, said Natterson-Horowitz - compulsive behaviors not dissimilar to OCD in humans. In animals, these behaviors are often related to grooming - as is hand washing in OCD patients.

Animals also have eating disorders. In thin sow syndrome, a pig going through a stressful transition will react by not eating. Some marine animals push on their stomachs to force regurgitation, and then ingest what they've just expelled. "It's a self-soothing phenomenon," Natterson-Horowitz said.

Many animal species experience adolescence in ways similar to humans: animals transitioning from immaturity to maturity will take greater risks, including approaching predators to inspect them up close.

Natterson-Horowitz and Bowers said that, as they looked for patterns and overlap, they were careful not to anthropomorphize the animals they studied. At the same time, they think researchers have been too cautious in the past about drawing connections between human and animal behaviors. Animals put under stress eat less, limit their diets, and eat at different times than they did previously. Patients with anorexia nervosa do the same thing. "I can't say it's connected, but it's very interesting," said Natterson-Horowitz.

And when they met with people in the animal world–such as stallion breeders at University of California Davis–a lot of the conversation made animals sound human. Plus, connections can be seen in the genetic patterns humans share with all kinds of species, from primates to algae.

Natterson-Horowitz and Bowers said that, on an everyday level, human doctors can learn from the techniques of veterinarians. Animal doctors must do a lot of their diagnosing through careful, holistic observation instead of relying on patient testimony and machines. Veterinarians, said Bowers, also tend to think about the environment and social structure a patient is embedded in more than human doctors.

In the question-and-answer session, subjects included the connections between plants and humans, animal S.T.D.'s, and depression.

One audience member asked: Will Natterson-Horowitz collaborate with botanists next?

She didn't say yes or no, but said that plants secrete certain compounds that make them taste bad to predators, similar to the way animals under stress–anxious lobsters, for example–secrete adrenaline that doesn't make them taste as good.

Bowers was surprised to find that S.T.D.'s occur throughout the animal kingdom - which makes sense when you consider the fact that animals are having unprotected sex with multiple partners. Studying an epidemic of chlamydia among koalas in Australia could prove helpful to us as we look at the koalas who are protected by certain genetic factors.

Do animals ever have depression? Yes, said Natterson-Horowitz. Geese, sea lions, and gorillas are among the animals who have exhibited depressive symptoms.

What's next for the Zoobiquity team? The two authors said they were looking at bullying in the animal world, and how it resembles the behavior you see in human schoolyards.

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