Unexplainable - Who let the wolves in?

Episode Date: December 11, 2024

Dogs were the first domesticated animal in history, emerging from wolves some 20,000 years ago. But how did wolves become dogs? To find the answer, scientists have to play with a lot of puppies. (First published in 2023.) Guest: Kathryn Lord, evolutionary biology researcher at UMass Chan Medical School For show transcripts, go to vox.com/unxtranscripts For more, go to vox.com/unexplainable And please email us! [e-mail] We read every email. Support Unexplainable by becoming a Vox Member today: vox.com/members Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hey, I'm Matt Bouchelle, comedian, writer, and floating head you may or may not have seen on your FYP. And I'm starting a brand new podcast. Wait, don't swipe away. It's called, That Sounds Like a Lot. You know that feeling when you check your phone, read a few headlines and think, That sounds like a lot. I can't do this. Well, I can, and I'm going to get into it every Friday.

You can watch on YouTube or listen wherever you get your podcast. I'm going to start by breaking down whatever insanity is happening in the world. And then I'll sit down with a comedian or actor or writer or, honestly, anyone who responds to my DMs. This is not the place to get the news, but it is a place to get the news. but it is a place to feel a little bit better about it. That sounds like a lot. Coming May 1st, part of the Vox Media Podcast Network. Oh, hi. Oh, hi.

Catherine Lord has a job that makes me jealous. You're just being silly. She plays with puppies for a living. Hi, buddy. How are we? Hey, hi. These are wolf puppies. Catherine sent me some audio she recorded during her research,

and you can hear one of the puppies climb into her lap. He's wagging his tail and wriggling around, and he can't sit still. At eight weeks old, he's small enough to fit in her lap. But he looks like a wolf, with a pointed snout and sharp ears. You're okay, you're okay. Here you go. Good boy, you can settle down. And there you go, it's a good boy.

Catherine isn't playing with wolfpups just for fun. As an evolutionary biologist, she's fascinated by what separates wolves from dogs. On one hand, they're very closely related. They share 99.9% of their genetics. They share an ancestor, and they can even mate and have fertile offspring together. But they're still very different animals. She told me you can even see that in a wolf puppy. They look more like tiny bears than tiny dogs.

But they also have a distinctive smell. They have more of a little bit of a musky smell, which is also very pleasant, but very mildly skunky is the closest thing that I can pick up, but in a nice way. But it's not just the way they look and smell. Wolves have a wildness in them that never really goes away. They also still have all of their natural hunting behaviors, which dogs don't have. So if I, for example, had a sore shoulder, I wouldn't go in with the adult wolves, even if I'd raised them, even if they knew me really well, because it could trigger their hunting behavior. Wolves tend to notice if you're hurt and they might attack you, which is the kind of behavior that would

be pretty concerning to find in a dog. And in the wolves, everything you greatly fear seeing in a dog pup is totally normal. And so you're like, oh, my God. Oh, no, it's a wolf. This is totally okay. Unlike wolves, dogs aren't afraid of strangers or other species like us. And it doesn't take long for them to make friends. It's kind of a superpower in the dog.

It takes about 90 minutes total between the ages of four and eight weeks for them to start soliciting attention or being like, hey, look at me from another species. But with wolves, for them to even tolerate being close to us, you have to have 24-hour contact with them for weeks on end when they're really young. Basically, as long as you can stand sleeping with them, at some point they start biting you in the ears when you're lying down. If you don't sit up fast enough, and you hear this wonderful noises,

these little... And then they chomp you in the ear, and you're like, oh! You don't sit up real fast. So we've got all these differences between wolves and dogs. But the bigger question isn't the what. It's the how. How did those differences evolve in the first place? For one, it's just a fun thing to think about.

They think it gets a lot of attention because we think dogs are cool. But there's a bigger potential prize here. Catherine says wolves became dogs because of humans, because of us. So figuring out exactly how this happened, could teach us how other animals might be able to survive in a world that we're drastically changing. A better understanding how this might have happened long ago, historically, evolutionarily, might give us a better understanding also

how animals and plants and such today might be able to or not able to adapt to us. I'm Manning Wint, and this week on unexplainable, how did we get the friendly and loyal dogs we know and love today from wolves? There's a story scientists tell about how wolves became dogs, but it's incomplete. So we think dogs evolve from an ancestral wolf, so something very wolf-like that is no longer around today. It's extinct, and it gave rise to modern wolves and dogs. We don't know exactly what these ancient wolves looked like or acted like, but we do know that both modern-day wolves and dogs come from them, because scientists have looked at the genes of all sorts of dog-like animals.

including jackals and coyotes, and they've mapped out how they're related. We can create these sort of family trees, these phylogenetic trees, based off of their genes, to see where they branch off from that ancestor. Evolution often happens at the scale of millions of years, but the leap from wolf to dog seems to have happened pretty quickly.

We're talking maybe thousands, tens of thousands of years, not millions or hundreds of thousands of years. This split happened, around 20,000 years ago, probably. Every time somebody comes out with a new paper, we have a new date. Some people think it happened more than once. Some people think it only happened once. And scientists aren't just confused about when it happened.

We really don't know where it happened. We have pretty much no idea, except we're pretty sure it wasn't North America. But the most important question here isn't where or when. It's how. There's a couple main hypotheses out there for how it happened. they can be split into two big categories. One category is probably the older of the two, is that humans took wolfpups, ancestral wolfpups,

out of the den and raised them by hand and purposefully bred them to be what we now think of as dogs. If this is true, dogs might have been a domestic invention, something our ancestors did intentionally before agriculture, before writing was invented, which is really impressive. But this would have meant raising wolf pups when they were really young.

They would have been barely walking, not eating meat yet, still drinking milk, because any older than that, and they'd just be uncontrollable. So the pups would need to be less than three weeks old when they got them. If they're less than three weeks old,

they need to be bottle-fed, but there wouldn't have been any bottles. So people suggest they would have been nursed by human women. This sounds horrible to me because they get teeth fairly early and they bite when there's not enough milk. And milk is just one of the issues here.

Once they're through that, they would need to feed them meat from their own resources and get them up to adulthood, hopefully without them killing any of their children while they're at it, because they still have all their hunting behaviors. Then they would,

would have to pick the friendliest wolves from that group to breed together, and somehow they'd have to go through the whole process for many, many generations to get this to work. Catherine doesn't love this hypothesis. It seems so unlikely. Our hunter-gatherer ancestors would have had to consistently keep a group of these dangerous wild wolves around them and make the nicer ones breed together. And it's not as if they would have known that they'd get dogs on the other side. She thinks the more likely scenario is that wolves chose to come closer to us

because we had something that they wanted. They were lured to us because of our garbage. You had wolves hunting in their normal environment, and they came upon a large amount of garbage and refuse and decided to see if there's anything tasty in there and got some leftover... something that they found acceptable to eat. Whenever people showed up, they probably ran away,

and so they didn't get a lot of resources out of that. But those animals that were able to stick around for a little bit longer did better scavenging out of those garbage piles. Something about these wolves made them just a little friendlier and more willing to get closer to us. And these are the ones that would get a little bit more food every day. Then, over time, through natural selection, you'd basically get those animals that were better able to stick around and eat that garbage without having to run really far away doing better. And so you'd have selection on surviving in this new environment, which would eventually lead us to dogs over time.

Catherine says this theory makes sense because there's an obvious benefit to the wolves here. If they found our waste as a source of food, they'd keep eating it. You can see this kind of thing happening today. All sorts of animals see trash as a source of food, including dogs. Most of the listeners will probably think about pet dogs, working dogs, dogs that are directly in contact with humans. But we think there's about a billion dogs on the planet

and upwards of 83% of them are living in garbage. dumps. If I think about that as the environment they adapted to, they're just like a lion on the Serengeti. Most of them weren't stray. They were born there. They adapted to that and do so well we can't get rid of them. But scientists don't know for sure whether humans domesticated wolves or if wolves did it themselves. Right now we have no way to definitively say one of those two hypotheses is correct because we don't have any way to go back and talk to the people and or look directly at it. So Catherine's not just looking at the past, but the present.

She wants to figure out exactly what makes wolves and dogs different today. Where are these differences come from biologically? If she can pinpoint the biology, then maybe scientists can explain how we got the dogs we know today. And that's where the wolf puppies come in. That's after the break. It's all about you. And when you fly with Virgin Atlantic in their upper class cabin, they take the VIP treatment to the next level.

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But he's recently run into some hot water because of his connection to Congressman Eric I have to learn from this, and I will learn from this. But, you know, for me, it's not a 2028 question. It's about what it means to be a better first boss in my office and also a better senator to my constituents. This week on America, actually, we asked Gallego about predatory behavior in Washington, his plans for immigration reform and more. You know, one time this wolf I saw?

Wolf. What's with all the wolf talk? Can we give it arrest for once? We can't go back in time to see how wolves But we can get some clues to better understand how it could have happened By comparing dogs to modern-day wolves This is what Catherine's doing. She's working with wolf puppies to understand their behavior And pinpoint precisely how dogs and wolves differ today. If we can't go back in time, what we can look at now is

what are the differences we see in dogs that make them special? And then how did those differences evolve in the first place? The biggest clue to understanding how you get really different behavior in such genetically similar animals might have to do with their first few weeks of life. So wolf puppies. When they're really young, dogs and wolves basically act the same. But by about a month, they're completely different. So the brain is developing very rapid.

rapidly, and what they experienced during that time has a really big effect on their adult behavior. This window of time is called the critical period of socialization. It's when wolves and dogs aren't afraid of new things yet. And this is the prime time to get puppies used to humans. So the beginning of this critical period is the ability to walk and explore. And so in dogs, we think that happens around four weeks of age. At that point, they're pretty much not frightened of new things. They'll just kind of bumble around if Godzilla showed up.

They'd be like, oh, what's this? So say this dog encounters a human for the very first time. They're going to register this human smell and hear their voice and see their arms and legs and face all in one go. When they're taking in all that information, they can take it in through all of their senses. And so they get a very full picture of the world. Dogs learn to love us pretty quickly.

But after wolves go through this period, they end up very different. Katherine has a guess about what makes this happen. But it's subtle. She thinks wolves might go through this critical period of socialization just two weeks earlier than dogs do. And when wolves start going through this period, they can only smell.

Sight and hearing turn on a little bit later, one at a time. And so what would happen then is they'd have a really good olfactory picture of the world. But as they go through this critical period, they're sort of layering on information about what it sounds like and what it looks like, which is not as solid a picture of things. So say a wolf puppy is just starting this period, and they meet a human. They register the human smell, and once they're used to it, they might just start liking us. But then they start hearing, and we sound really scary, but they compare that to what we smell like.

And then they start seeing, we look really scary, but they compare that to what we sound like and what we smell like and keep going. So basically the whole thing we get interrupted. by the development of the senses. Dogs also develop their senses one by one, but their critical period of socialization starts later when they have all their senses already turned on. But Catherine thinks Wolves start this period earlier, when they can only smell,

so they have a more jarring experience. And this would really explain a lot of those behavioral differences. It would explain why dogs are so easy to socialize because they have a full picture of a huge during that time period, and so they just need to get an idea of what it sounds, smells, and looks like, and then moving forward, they're good to go on any of those things. Catherine thinks this difference of two weeks, this tiny developmental shift, could be the root of what separates dogs from wolves.

But it's still just a hunch. So she's trying to figure out exactly when this period starts and ends. What we're interested in finding out is when do dogs and wolves start walking? and when do they avoid novelty? To find when the critical period starts, Catherine's putting accelerometers on puppies that track their movement. We put a little harness on the wolves, and it looked like they were going to their first day of kindergarten.

They look like they have these little backpacks on. It's kind of ridiculous. And to measure when the critical period ends, she's trying to figure out when puppies start being afraid of new things. So she puts wolf puppies in a little arena with an object that they've never seen before. And so then we can compare the dogs and the wolves and how much fear they show,

how much time they spend with the object, and when they go, yeah, no, I don't want to check out that novel object anymore. After all these experiments, if this two-week difference proves to be true, the story of how wolves became dogs could be something like this. Something like 20,000 years ago, ancient wolves may have come across our roving camps and garbage.

Most of them would have been hyper-cautious of us, and they would have stayed away. But there might have been some wolves that risked getting closer and got more scraps. There could have been something biologically different about these wolves. Specifically, they might have started their critical period of socialization a little bit later. So if that difference was a slight change in the critical period, those animals would do better, be more likely to reproduce, be more like they have offspring. So those offspring would then inherit that slightly different critical period and experience their life maybe a bit closer to people.

Generation after generation, there'd be incremental shifts in this critical period until one day you'd have these puppies that start this period when they could see, smell, and hear the world. And boom, you'd get this giant change. Where those animals were now animals that could easily socialize with people, easily generalize, easily be okay with novelty. And this shift might have set the stage for them to eventually evolve into dogs. It's something I find endlessly exciting that you could have just a two-week shift in something

very early on and get this huge behavioral difference, just an entirely different animal at the other side. This is still only a guess, just one possible story for what could have happened tens of thousands of years ago. So Catherine not only has to figure out if that two-week shift between wolves and dogs exists, she also has to figure out what's going on in their DNA. She's currently working with geneticists to find what genes are involved in this critical period. Eventually, if we can figure out genes or genetic mechanisms that are tied to this shift,

and we could look at ancient remains and say, okay, do they have these differences that we are associating with dementia, that might help us get down to the question of where and when and how. That will be in the distant future, but eventually it might help us answer that question. Catherine's work is foundational, and it'll help us get clearer on these bigger questions. But for her, studying this evolutionary story goes beyond dogs and wolves. If dogs evolved because of our literal piles of garbage, there's something to learn about how any animal adapts to the changes that we've made in the natural world. If we look at all life on the planet right now, it's having to deal with our disturbances, with our changing ecosystems. And some animals

are doing really well with that. Well, other animals are doing really poorly with that and going extinct and endangered and not able to keep up with this pace. So a better understanding how this might have happened long ago, historically, evolutionarily, might give us a better understanding also how animals and plants and such today might be able to or not able to adapt to us. Humans are deeply involved in the evolution of other animals, whether we want to be or not. And in a way, we did create dogs. We welcome these ancient dogs into our homes, and now we can't imagine our lives without them. But it probably had less to do with our intentions than it did with the craftiness of evolution. If we think about dogs as something we create,

we tend to think of them as something degenerate, something that we made, something that we were under control of. I find it a bit egotistical that we think we could have somehow been like, aha. Back before we knew what domestication was, we went, you know what would be great if we had this thing that could herd sheep and bark at people and sleep at my feet and front of the fireplace. What's a fireplace? I don't know. instead of this really fascinating evolutionary story that a byproduct of our existence is garbage and refuse, it just is. We create a lot of stuff that animals and plants and microbes then take advantage of, and a lot of animals survive off of it today, including dogs. We are not separate from evolution.

We like to think of ourselves as something special above. We are just something else in nature that's happening, and evolution acts on that, too. Life just keeps adapting. This episode was reported and produced by me, Manning Wann. There was editing from Brian Resnick and Meredith Hodnott, mixing in sound design from David Herman, music from Noam Hassanfeld,

and fact-checking from Serena Solon. Special thanks to Eleanor Carlson and the folks at Wolf Park in Battleground, Indiana. If you have thoughts about this episode or ideas for the show, please email us. We're at Unexplanable at Vox.com. Unexplainable is part of the Vox Media Podcast Network, and we'll be back next week.