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For a long time, scientists have believed that we taught dogs to play fetch. In other words, it's thought that dogs acquired some of their unique abilities to interact with humans after they were domesticated from wolves.

And that includes things like playing fetch. But research published last week in the journal iScience showed that wolf puppies can play fetch without any prior training -- which made the researchers think that this behavior helped us domesticate dogs in the first place. At least fifteen thousand years ago, humans began domesticating dogs from gray wolves.

Fast forward to now, and there are everything from shih tzus to St. Bernards. Physical changes like snout size or leg length are pretty clear markers of that process.

Behaviors, like playing fetch, are harder to measure. So it's not always clear when or how they emerged. These researchers weren't specifically trying to make fetch happen.

Rather, they were interested in demonstrating that non-domesticated animals could interpret a social-behavioral cue from humans. As in, they could understand, like, “Go get the ball!” Now, the ability to act on a human's social cue is not unheard of in animals. Previous research had shown that animals like horses, birds, pigs, and even bats could follow human cues if they expected some kind of food reward.

But those animals usually had some kind of training or familiarity with that person beforehand. In this study, the researchers got rid of the food reward and just wanted to see if wolves would play with them. That would demonstrate that they had some innate ability to follow human directions.

The Swedish research group hand-raised 13 wolf puppies starting at 10 days old. And this has nothing to do with the outcome, but they named them all after famous musicians, which is kind of cute. The puppies were socialized to get along with humans, and given lots of space to play.

When the wolves were 8 weeks old, the researchers gave them the Puppy Mental Assessment, which is a standardized test that some dog breeders use to match their puppies to good owners. The researchers brought each puppy into an empty room where a stranger, someone they hadn't met before, gave them that test. One piece of the assessment calls for the tester to throw a ball and then encourage the puppy to return it — which us normies call playing fetch.

Now, not all of the puppies returned the ball. Two of them, Lemmy and Elvis, returned the ball twice, while another one, Sting, returned three out of three balls. Good job, Sting!

Many of the other ten, including Ozzy and Hendrix, had no interest at all. But the fact that any of them could follow human directions without training was still surprising. It made the researchers think that this kind of social behavior is something that already existed in wolves prior to domestication.

Just not all wolves -- only some of them. So humans would have started with the more social wolves, then selected for that kind of thing over the years. In other words, we didn't teach dogs how to be social -- that trait already existed, and we made it more prominent.

But let's make one final thing clear: This is an experiment, these are scientists - wolves do not make good pets. Please do not go out into the woods, find a wolf and name it Björk, and play fetch with it. In other news, according to a paper published last week in the journal PNAS, certain plant cells might be immortal by default -- or at least incredibly long-lived.

And their graceful aging might be a clue to how cellular aging works in general. Plant cells, like our cells, undergo senescence, a process of cellular events that keeps aging cells from dividing. It's part of a defensive strategy meant to keep damaged cells from growing out of control, which is what happens with cancer.

Senescence itself is the final stage of aging, which looks different in animal and plant cells. When we animals age, more of our cells start to senesce -- meaning that their division slows dramatically. But in plants, it's associated with things like tissue degradation.

You know, like leaves falling off in autumn. That's all fine and good -- but senescence at the level of the entire plant means it probably isn't going to have much longer to live. In this study, the researchers were interested in the plant's cambium meristem, a structure in the stem that cranks out fresh new cells for the tree to use through the entirety of its life.

But the cambium meristem can help the tree regrow damaged or broken parts as long as those cells remain active -- theoretically for the lifespan of the tree. Which led the researchers to ask: Could the production of new cells from the meristem help the tree avoid senescence and stay alive forever? They studied a species of giant tree in China, the Ginkgo biloba, which can live to be a thousand years old or more.

The researchers took samples from 34 ginkgo trees ranging from just 15 years old to over 13 centuries old. From those samples, they were able to examine the size and structure of the cambium meristem in various ages of trees. And they expected to see layers of new cells added to the cambium meristem every year that the tree lives.

As trees got older, they added fewer and fewer layers every year, until they hit 600 years old. Then, the rate of new cells being added evened out and never dropped. It might've been slower growth than when the tree was younger, but the cambium still grew, even after half a millennium, and that may have helped the tree avoid senescence.

The researchers backed this up by showing that genes involved in senescence aren't expressed any more or less often in old trees compared to young trees. These genetic features might give ginkgo the ability to avoid senescence and live virtually forever. But unfortunately, plant and animal cells deal with senescence differently.

So while this experiment uncovered some cool plant biology, we're not going to be using the results to chase down immortality in humans. Thanks for watching this episode of SciShow, which is produced by Complexly. If you want to keep imagining the world complexly with us, you can check out the Crash Course Business: Entrepreneurship.

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Over 17 episodes, Anna will explore how to take an idea and grow it into a thriving business. The first video can help you figure out if you want to be (or already are) an entrepreneur. We've linked the whole playlist in the description, so check it out! [OUTRO ♫].