How dogs evolved to be man’s best friend
There is a good chance that many of you watching right now have a dog somewhere nearby. But what do you actually know about where dogs come from? You're probably aware they evolved from wolves, but how? And when? It turns out much of that is still a mystery.
There are some intriguing clues however that have been discovered in the DNA of dogs and wolves. Clues that just might give us a better understanding of how they, and we, evolved. You've heard of survival of the fittest, but a scientist at Duke University says the term that may best describe dogs' evolutionary success is survival of the friendliest.
There is no doubt, dogs are an evolutionary triumph. There's an estimated billion of them on the planet and they've nosed their way into every corner of our lives. Living with us, working with us and loving us.
Anderson Cooper: What is it you're trying to understand about dogs?
Brian Hare: I'm really interested in where dogs come from. And I think it teaches us a lot about where humans came from.
Brian Hare, an evolutionary biologist and author at Duke University, has spent the last 25 years studying animal evolution.
Researcher: Puppy, look.
Brian Hare: I think what really summarizes the link between dog and human evolution is survival of the friendliest.
Anderson Cooper: What about survival of the fittest?
Brian Hare: So survival of the fittest is a misconstrue, really, in the public mind of what evolution is. It's, like, the idea that, like, "The biggest, the strongest, are always the one that win."
Anderson Cooper: "Might makes right."
Brian Hare: Yeah, but not at all. And dogs are Exhibit A of this.
Hare says it may be hard to imagine, but that sweet dog you love started out as this: a wild, predatory wolf. And their evolutionary story began at least 20,000 years ago, when humans were hunter-gatherers.
Brian Hare: So what we believe happened, and we have science to show some of this, is that wolves chose us. A population of wolves actually became attracted to humans, and they were at an advantage because they were eating garbage things that people were leaving around home. And that the wolves that sort of basically gave up on being wolfy and hunting, and were attracted and friendliest towards humans they were at a huge advantage.
Anderson Cooper: Some wolves were able to feed off scraps, they weren't aggressive, and over time they became domesticated?
Brian Hare: That's exactly right.
To better understand how the two species diverged so drastically, Brian Hare came here, to the Wildlife Science Center in Minnesota.
It's run by director Peggy Callahan and her 23-year-old daughter, Meg -- both skilled, we saw, at navigating a cage full of hungry wolves.
There are 110 gray wolves here. Some were rescued from the wild, but most were hand-raised by Peggy and Meg. They're divided into packs, separated by chain-link fences. This pack is named after the 80s horror movie "Children of the Corn."
Anderson Cooper: So, I saw the movie "Children of the Corn," which is terrifying. Why is this pack called "Children of the Corn?"
Peggy Callahan: For terrifying reasons. They attacked and killed their father. And then tried to kill their mother, so.
Anderson Cooper: This pack–
Peggy Callahan: This pack.
Anderson Cooper: Why did they kill their father?
Peggy Callahan: Opportunity.
Anderson Cooper: Opportunity?
Peggy Callahan: Yeah.
Anderson Cooper: Wow.
Peggy told us the only reason we were able to sit among the Children of the Corn is because these wolves view her as the dominant member of their pack.
Anderson Cooper: Why is it important that in their mind, you are dominant to them?
Peggy Callahan: The reverse is quite dangerous. I know that they're capable of killing one another. Their teeth are-- their jaw pressure's enormous.
Anderson Cooper: By the way, even right now, with the wolves coming up behind you, you're aware they're behind you--
Peggy Callahan: Yes. We have to have eyes on the back of your head.
Anderson Cooper: They're assessing who are we? Who's dominant? Could I take this person?
Peggy Callahan: Absolutely. Yeah. And what I don't. Hi. I don't think they're planning anything, but I think, should an opportunity afford, they're incredible opportunists.
Peggy works hard to secure the upper hand. If you have any doubt about her position as the alpha dog, just listen.
Anderson Cooper: Can you show me your howl?
Peggy Callahan: Absolutely.
Peggy Howling…. Wolves Howling
Meg Callahan: Goosebumps every time.
Anderson Cooper: That was so cool.
Peggy Callahan: Now, wouldn't you learn to howl if that happened?
Anderson Cooper: What is the significance of the howl?
Peggy Callahan: They use it to mark territory. They also will howl at intruders to get them to leave.
Becoming dominant over a wolf starts early, if a pup needs to be taken away from its mother for health or research purposes, Meg steps in.
When we were there with her in May, she was taking one-month-old Philo everywhere, even the morning coffee run.
Meg Callahan: Sometimes if he gets really mouthy. Ouch. Like that. Enough. (Growl) Good boy.
So it's just a little correction. I just pinch and I growl. And then, the second he stops growling, I whine to him and rub his belly and stuff.
Anderson Cooper: That's what his mother would do?
Meg Callahan: Exactly. Yep. (Meg growls) I'm sorry. There was some wolf that looked just like you that was back-talking me there. Not you.
But don't be fooled, dominance has its limits. This is MJ.
Anderson Cooper: This is the dominant female?
Peggy Callahan: Yes.
She was also hand-raised and likes a belly rub too -- that is, until she doesn't.
Peggy Callahan: She's tolerating this with us. I'm mean, she's…
Anderson Cooper: Right.
MJ lunges at Anderson's hand…
Peggy Callahan: She's-- I mean, she's-- oh-- oh, no she's not.
Peggy Callahan: OK. Enough. Ok. Ok. She just said, "Stop."
Anderson Cooper: I heard.
To see just how far dogs have evolved because of domestication, at Duke University, Brian Hare has set up a "Puppy Kindergarten."
Students help raise labrador puppies -- they tag along -- cruising the quad. Going to basketball practice. Even the track team's photo shoot.
Part of the program is aimed at training service dogs for the organization canine companions.
But there is research being done too. To compare the puppies to hand-raised wolf pups, Brian Hare's team runs them through a series of behavioral tests.
Researcher: Look. Look. Look. OK.
Puppy follows point.
Researcher: Yes. Good job.
This puppy looks back and forth from the researcher to the bowl and then immediately follows her point.
Philo, the wolf puppy, might look like a dog, but watch him take the same test.
Hannah points for Philo.
Hannah: Puppy look. OK. OK baby.
Brian Hare: So you can see Philo didn't follow the point here.
Anderson Cooper: But a puppy this age would?
Brian Hare: Totally. Exactly. So it looks like dog puppies come into the world kind of prepared to understand us in a way that wolf puppies are not. Because of domestication and interacting with us.
Anderson Cooper: You've done testing with dozens of wolves. Overall, what have you found?
Brian Hare: So, you can spend 24 hours a day with say a wolf puppy and even after you've done that for several months they're not attracted to new people, they don't want to be with people. They want to be with wolves. That's not what happens in the case of dogs. As a species, they're actually what's known as xenophilic, they are attracted to new things and new people.
But how much of that is in their genes? Back in 2010, to figure that out, Hare's colleague, Bridgett vonHoldt, a geneticist at Princeton, started comparing the DNA of dogs to wolves.
Anderson Cooper: You've located some specific genes that lead to friendly behavior?
Bridgett vonHoldt: That's right. When we sequenced a bunch of dogs and a bunch of wolves we used that to then search for mutations in the dog genome that only dogs had and we came out with a really nice hot spot of mutations on chromosome number six in the dog genome, and that's what's highlighted here.
Anderson Cooper: You can actually pinpoint genetic mutations in dogs that make that dog friendly to humans in a way that wolves are not?
Bridgett vonHoldt: Absolutely.
Anderson Cooper: Wow.
Bridgett vonHoldt: This was a major finding in my opinion.
Anderson Cooper: And that is something that would have evolved over time?
Bridgett vonHoldt: That's right. So we can imagine back in the pre-dog era where there were wolves running around, and some of those wolves were maybe making their dens closer to human settlements. I hypothesize that if I could go and sequence those wolves that they would carry maybe two of these mutations and the rest of the wolves maybe none.
Bridgett vonHoldtcalls these "friendliness mutations."
Anderson Cooper: So does my dog really love me? Or is my dog just acting out on its genetic code?
Bridgett vonHoldt: She absolutely loves you. She has the genetic predisposition to wholeheartedly love you more than she probably can handle.
What came next in vonHoldt's research stunned her and us. She found the location of the friendliness mutations in dogs corresponds to the same genes that, when deleted in humans, cause a rare condition called Williams Syndrome. Her study established one of the first genetic links in behavior between dogs and humans.
Meet 36-year-old Ben Monkaba.
Ben Monkaba: How are you, sir?
Anderson Cooper: I'm well. How are you sir?
Ben Monkaba: What a surprise.
Ben is no stranger to 60 Minutes, when he was 11 in 1997, Morley Safer met him doing a story on Williams Syndrome.
Clip from "A Very Special Brain"
Morley Safer: I'm Morley
Ben Monkaba: Morley Safer?
Morley Safer: Yes, himself.
Ben Monkaba: How are you?
People with Williams Syndrome, like Ben, are often unusually outgoing and friendly, leading some to call it "cocktail party personality."
We were with Ben at his favorite pub when he jumped up mid-dinner to join the band.
Anderson Cooper: What is it that makes you unique?
Ben Monkaba: What makes me unique is my way of giving happiness to people, my friendliness, my kindness.
Anderson Cooper: I gotta say just meeting you, you made me smile the moment we met.
Ben Monkaba: When people are happy, it makes me feel like I've achieved something.
Williams Syndrome is a lifelong condition that often causes serious medical problems and intellectual disabilities. Ben's mom Terry Monkaba says Ben, and others like him, are so trusting and friendly they can sometimes be taken advantage of.
Anderson Cooper: Could you just explain what is different about Ben genetically?
Terry Monkaba: Sure, Ben is missing 25 genes on chromosome seven. And all of those genes line up. So that's, you know, 1/10th of 1% of their genetic makeup that is missing.
That deletion in Ben's DNA -- and others with Williams Syndrome -- involves the same genes that contain the friendliness mutations discovered in dogs.
Anderson Cooper: Ben, what do you think about that, about-- that there might be a link? Friendliness in dogs, there might be a link to friendliness in humans?
Ben Monkaba: Wow. It just makes me feel so happy and proud that dogs and people have similarities.
When the discovery was announced in 2017, Terry was head of the Williams Syndrome Association, she reached out to some members to see how they felt about it.
Terry Monkaba: And one of the parents that I called said, "Are you kidding? You know I'm sure that, if a tail was put on my son, it would be wagging all the time," you know? And so-- and I think that really put it into perspective.
Understanding why dogs are so friendly, Brian Hare tells us, is helping unravel the mystery of how homo sapiens came to be the most dominant species on Earth.
Anderson Cooper: So what does our understanding of dog evolution tell us about human evolution?
Brian Hare: I think what dog evolution teaches us is that actually how you get ahead in the game of life, is you evolve a new way to be friendly that leads to a new form of cooperation. Humans 100,000 years ago, our species, was not alone. There were at least four to five other human species. And the question then becomes, "Well, why are we the only one left?" And we think, and what dogs point to, is that we were the friendliest species that ever evolved among humans, and that we survived because we are friendly.
Survival of the friendliest, a successful evolutionary strategy many humans today would be wise to remember.
Produced by Denise Schrier Cetta. Associate producer, Katie Brennan. Broadcast associate, Annabelle Hanflig. Edited by Matthew Lev.
Anderson Cooper, anchor of CNN's "Anderson Cooper 360," has contributed to 60 Minutes since 2006. His exceptional reporting on big news events has earned Cooper a reputation as one of television's pre-eminent newsmen.
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