【高级听力】（文末附视频）Why Dogs Age Faster Than Us

Why Dogs Age Faster Than Us

《文 末 附 视 频》

This may not be a word-for-word transcript.

Now, for some fast facts: The longest-living person was a woman who made it 122 years and 164 days, which isn’t bad for a species with an average lifespan of 72 years. There was also a cat that set the record for the feline community by living to 38 years. Yet dogs aren’t so lucky, which means we humans, who’ve dubbed these loveably goofy creatures as our best friends, really feel the sting. A 13-year-old person has their whole life ahead of them, yet a 13-year-old dog is considered a senior at that age. While we humans take up to 18 years to stop growing and developing, a dog is usually full grown at 18 months.  

Canines do have their own record-setters. An Australian Cattle Dog born in 1910 lived to be an impressive 29 years old. Impressive, given that most dogs live on average from 10 to 13 years, depending on the breed, of course. Lifestyle and health play an important role as well, but that’s another story.

We’ve all heard the statistic, “1 dog-year equals 7 years for a human.” But the 1:7 thing isn’t as simple and universal as it’s often quoted. It’s more like: for the 1st year of their life, dogs age 15 human years. Then they age about 4 human years with each birthday. After 6 years of life, the larger breeds start aging at a faster rate. And this can help explain why a Great Dane is pushing it at age 10, yet a Chihuahua can double that. But the question is: why?

Scientists have been trying to figure that out for decades. And not just about larger breeds living shorter, but dogs in general. What sets the limits? And why do cats outlast our canine friends?

These questions were first asked by Aristotle back in the BCE times. They obviously didn’t have the technology or medical knowledge we now do, so the philosopher suspected that the reason was moisture. He believed that elephants, for example, lived longer than mice because they contained more liquid. Of course, the moisture thing wasn’t right, but his observations were pretty accurate overall: bigger animals do tend to live longer than smaller ones. For almost a century, people believed that creatures with faster metabolisms don’t live as long because their bodies get tired. But that’s not entirely correct, either, at least according to experts who study aging in animals and humans. Let’s consider our parrot friends. Their hearts beat up to 600 times per minute, yet they have an average lifespan of 20 to 50 years. Their size has a lot to do with that, but they still outlive many other creatures with slower heartbeats (and thus, metabolisms) by decades.

Another theory on why some animals live shorter has to do with these things called free radicals. These are toxins in our environment that we’re exposed to every day. Over time, they damage cells and cause aging. So, if you think about larger animals that have more cells in their bodies, then they don’t feel the adverse effects of these free radicals as dramatically as small animals with fewer cells do.

Larger species living longer could simply be a result of where they stand on the food chain. Take elephants and whales, some of the most massive creatures on this planet. It takes them longer to grow because hardly anyone would dare to attack them, right? Whereas mice and other small targets that are easily preyed on live life in fast-forward. They rush to grow up and reproduce ASAP so that their species doesn’t go extinct. OK, but those are all animals that live in the wild, not in cozy houses with people to take care of them.

So, why don’t dogs live longer?

Well, for one, dogs haven’t always been our pets, but we do have a long history together. Humans and canines have been friends for thousands of years. DNA suggests that wolves and dogs split around 100,000 years ago. The oldest solid record that shows dogs were domesticated was about 14,000 years back. So it’s not like we just started welcoming full-blown wolves into our homes. We adored our new pals so much that we even painted them in some caves in Saudi Arabia 10,000 years ago. But some scientists believe we domesticated our canine friends long before that. Maybe that’s why they don’t live very long? We’ve been spoiling them with the comforts of domestic living, not to mention cross-breeding them to make adorable new designer types: Maltipoos, Chiweenies, Puggles. Have we messed with their ancient wolf DNA a little too much? It’s a reasonable question, the only problem is: wolves only live 6-8 years. Yeah, not as long as dogs. Well, the harsh conditions of the wild probably have a lot to do with that.

There’s a theory suggesting that dogs don’t live as long because they’re just so sociable. They live in packs, right? The way it usually goes is when a species lives in groups, they’re more likely to spread illnesses, whereas cats evolved to protect themselves from predators, and we can see that today, too. This independent nature can prolong an animal’s lifespan by about 3 years. Hence, why Whiskers usually makes it longer than Fido.

There are other smaller creatures that live longer because they’ve been able to avoid dangers. What comes to mind are bats and mole rats, which kinda look like mini hairless walruses. Both have an average lifespan of 20-30 years.

Now that we’re on the topic of smaller species, it gets more complicated, especially because some small dogs outlive larger ones. A 150-pound Irish wolfhound is lucky if they make it past the age of 9. But an 8-pound Papillon will usually surpass a decade of life.

Here’s where size can have a negative effect on health. Large dogs grow faster, right? Well, their bodies also need to carry more weight, and their hearts must work hard to keep all that mass working smoothly. Large species like Saint Bernards and German Shepherds are more prone to hip dysplasia. Siberian Huskies can often develop immune problems. 

Also, some breeds are younger than others, and they haven’t had enough time to evolve. The good thing is that our favorite animals are living longer these days than they used to. It could be genetics, or, like for us humans, more developed medicine and better-quality foods may be playing a role in prolonging lifespans. 

Whatever it might be, over the past 40 years, both dogs and cats are living twice as long than they used to. Maybe it’s those cute little sweaters we put on them in the winter? Nah!

Now, earlier I said “goofy” creatures for a reason, and you know exactly what I’m talking about! Does your dog take a treat or a big cheekful of food from its bowl only to carry into another room to eat? Like a lot of strange things your dog does, it’s ancient instincts controlling their brain. It goes all the way back to wolves and the pack mentality. Dogs are social animals with a clear understanding of hierarchy. In that small society they formed, each member of the pack had its own social order. There’s the leader who makes all the important decisions, like when and where to hunt, when they rest, when they can eat, and who can eat. Domesticated dogs follow the same hierarchy rules, and they recognize their owners as the pack leader. So, when you give them food, they prefer to take it to another room so you won’t try to steal it. 

And that circling ritualistic thing they do before they lie down? Again, this isn’t something they learned but a result of their wild instincts. Spinning in circles might happen for several reasons. One is to prepare the ground and make it comfy. The other is to position themselves in the right way to prevent an attacker from getting to them. Or in my dog, Riley’s case, it’s to occupy the majority of the space on the bed. 

What about rolling around in the grass like a goofball? Several reasons for that. The first one is because it’s nice and soft, and it feels good. Even I do that! The second is to get rid of dirt and debris off their back – the grass is a perfect cleaner. But the third is one you might not see coming when you’re staring at your little Yorkie rolling around the yard: it’s their predatory DNA. When they smell something in the grass they can hunt, they’ll use the grass to mask their own scent and sneak up on their prey. Most of the time, though, they’ll do it instinctively and then forget about it. 

Crazy dogs – gotta love ‘em!

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