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TERRY GROSS, host: This is FRESH AIR. I'm Terry Gross. Our guest, Mark Derr, is a naturalist and writer who's been thinking about how dogs evolved from their prehistoric ancestors, and how they came to have such a close relationship with humans. Derr believes new genetic and archeological research suggests our friendship with dogs and wolves goes back thousands of years farther than previously believed.

In his new book, Derr explores how the relationship developed, and how it influenced the physical evolution of dogs from wolves, into the friendly creatures that are so much a part of our lives. Mark Derr's book is called "How the Dog Became The Dog - From Wolves To Our Best Friends." He spoke with FRESH AIR contributor Dave Davies.

DAVE DAVIES: Mark Derr, welcome to FRESH AIR. Now, in your book, you tell us that there's new research from genetics, and from the archeological record, that's changed our views - or at least challenged the view that we've traditionally had, about how dogs - or their dog ancestors and humans became acquainted thousands of years ago. What was the traditional view of how dogs and people got together?

MARK DERR: Well, by traditional view, I use the one that's most current today and appears almost everywhere in print and on television programs. And that is that the dog somehow is a self-domesticated animal who fed on garbage dumps as people began to give up their hunting and gathering ways at the end of the last ice age, and move into semi-permanent villages - that these wolves were scavenging their dumps and the more they scavenged, the tamer they became and ultimately, they became these self-tamed dump-divers, I call them, who people then took into their homes, or began to use in ways that more resembled their wolfish past.

If you think about it, it's a bit convoluted, really. Many animals feed on garbage dumps. None of them really get taken with welcoming arms into our homes and lives.

DAVIES: So we now believe that - or you believe that wolves became socialized and ran with humans before they began settling down to villages, when they were still hunters and gatherers, right?

DERR: I take the view that the dog is an evolutionary inevitability, that as soon as wolves and humans met on the trail of big game, they started traveling together, and they've been at it ever since. I say that because there are wolves who are highly sociable, just as there are humans who are highly sociable. And those two highly sociable individual animals, in many cases, could get together. And from that, could rise all kinds of relationships.

What I'm saying is that the dog is a creation of wolves and humans, of two equal beings who have come - who came together at a certain time in history, and have been together ever since.

DAVIES: Now, I notice that when you're discussing this early relationship between dogs - or dogs' ancestors - and our ancestors from prehistory - early humans - you prefer the term dog-wolves or dog-like wolves to wolf-dogs. What's the distinction you're making?

DERR: The distinction I'm making is that there were some wolves, I believe, who were indeed dog-like; that is, they were highly sociable to humans; they liked to hang around humans; and they ultimately settled down, in a way, in that they might have a litter of pups near the human society.

Some of those pups, being highly sociable, would take up with the humans and on down the line, so that what's being selected for is not tameness toward people but sociability, the sociability of certain types of wolves and humans.

Now, that said, we're talking about a wide spectrum of behavior on the part of both species. There certainly are humans who are not very sociable, either to other humans or to other animals, just as there are animals who could care less about humans. There even are some dogs who really, basically, don't care very much about humans, it seems.

And so what I'm suggesting is that the dog emerged from a group of wolves who were basically dog-like - who were sociable to humans, who would interact with them, hunt with them, travel with them and ultimately, began to reproduce in their presence.

That's not to say that all those dog-wolves, mind you, went on to become dogs, because many of them could die out. They may not have found mates; the lines may have vanished or been replaced by other lines. So we're talking about two things, really. One is the way in which wolves and humans got together and lived together. And the other is how these wolves, these sociable wolves living among humans, ultimately became dogs. And that's the challenge.

DAVIES: When humans began associating with wolves - you know, back many thousands of years ago - and then, of course, physical changes occurred that made these creatures the dogs that we know today. What were some of the changes that came with living with humans?

DERR: Traditionally, what archeologists have found and used to designate an animal as a dog, versus a wolf, is an overall reduction in size, a shortening of the jaw, crowding of the teeth, and other features that would indicate that it was a small kind of wolf. This fed into the argument that the dog was basically this juvenilized, self-taming wolf - a kind of wolf-light, as it were.

Research that's coming out now would tend to indicate that a small number of genetic mutations can have a large effect on an animal, so that researchers have found a gene for - that seems to regulate smallness in dogs.And one of the first divides, I think, in the world of dog is between large and small.

DAVIES: So how could this association of wolves with humans lead to these physical changes?

DERR: Well, what happened was that you had populations of dog-wolves that became isolated from the greater wolf population and in doing so, they began to breed more closely - to inbreed, as it were.

And when you inbreed, you get genetic peculiarities that arise, and those peculiarities then begin to become part of that population. If they work, if they're popular, if they have some function of beauty or utility, then they are kept by the humans. And that population then spreads those through other populations, through breeding.

DAVIES: But if you look at these changes that kind of typify a dog from a wolf - the shorter snout, the smaller size - were these changes that were adaptations to living with people? I mean, less powerful jaws, I believe, was another one you mentioned. Or were they simply...

DERR: Yes.

DAVIES: Yeah, why would living with human beings reinforce those changes?

DERR: Well, there are several things, one at the end of the last ice age. There seems to have been a pretty across-the-board reduction in size of many animals, including humans. It also was the case that the change in diet would have an effect on the way the jaw is shaped because an animal that's not crunching bones all the time, or is feeding on grain, wouldn't have the need for as strong and powerful jaws as one that's living by hunting.

This, by the way, is a phenomenon that occurs among captive wolves, also. You must bear in mind that some dogs have a more powerful bite than wolves do. So we've been able to create animals that are both weaker and stronger, and that's purely a matter of selection by people for traits they want.

In other words, a mutation will appear in a small population. If I don't want it, what I do is kill the animals so that they don't reproduce. If I do want it, I try to get them to reproduce.

DAVIES: So just going back to kind of the earlier years of this, so when dogs got smaller, after their association with humans, why was that? I mean, wouldn't big dogs have been more effective - just as effective or even more effective hunters?

DERR: Well, not for getting rats. So small dogs are useful in terms of killing rats, really, and they also - there have been people who have suggested that the small dog was - in itself - because of its size, a curiosity, an easier dog to have as a companion.

In much of history, even in the American South through the 19th century, even today, you'll find people who have two dogs, or several dogs, but the divide they have is between a large dog, who is in the yard, and a small dog. And the small dog is usually as a feist or a little terrier or some sort whose job is to kill rats, make a noise if somebody comes near, be a companion or playmate for the children, and a guardian.

There's one story that I ran into many years ago, and used in a previous book, of a woman who was out picking beans, and her little terrier was out there and started making an unholy racket. And she looked up and finally saw that it was barking at a big panther who was staring at her child.

She scooped the child up and ran in the house while the little dog stayed outside to hold at bay this big cat. Well, unfortunately, the cat ate the dog. But the husband, when he came home, took his big dog and went out and hunted the panther and killed it - and found the remains of their little dog, who had been very courageous.

DAVIES: How did the association with wolves begin, do you think?

DERR: Well, there are two ways I think that this could happen. One is people taking in puppies who were orphaned, perhaps, or they stole them. There are any number of ways to obtain wolf pups, and people have been doing it for a long time. And it is fairly easy, if you get them at a young age, to socialize them to humans - those who are so inclined.

But I think beyond that, there were adult animals involved. This is a bit of heresy but if you think about it, it makes sense. There were researchers in the United States during the 1960s who were able to socialize adult wolves. And they did it in a very interesting fashion; that is, they would go into the pen and let the animal decide to come to them. They would not force themselves on the animal.

Now, those among our listeners who have actually interacted with adult animals, and had them become friendly toward them, will understand what I'm talking about. I did it with a heron, for example. You can do it with all kinds of animals. But you have to allow the animal to come to you and not pose a threat to it - or a perceived threat. And after a while, it will accommodate itself to you if it's so inclined. I think this happened with wolves, also.

Beyond that, the issue is this - and we always have to bear this in mind - biological time is infinitely short compared to geological time. And so you can fracture the structure of a wolf pack or a dingo pack in no time at all, simply by taking out the breeding pair. Take them out of the equation and certainly, you've lost wolf culture for those younger animals, and they have to learn how to behave. If it happens in a way where they're with humans, they can learn from humans how to behave.

DAVIES: Now going back to, you know, the early association of humans and wolves, to what extent was it that they learned to hunt together? I mean, either the way modern hunters do, or perhaps humans following wolves, who had a better scent and could track some of their - you know, the game that they mutually sought. How much of it was a utilitarian alliance?

DERR: There have been people who have suggested that wolves taught humans how to hunt. I'm not sure that's true, but I think it is true that humans, if you - humans could follow wolves, for example, as they pursued their game, and then move in at the last minute to make the kill rather than allowing the wolf to do it and cart off the meat.

They might throw game to the wolf, or they might not. In that case, it's simply a case of following the leader, and the leader is the wolf. The wolf, on the other hand, could look at the human and say: These people are far more profligate hunters than we are. When they go out, they always leave a surplus. And it's easier for us to take the scraps that they have than it is to hunt. Hunting is a highly energetic activity.

And so they could learn from each other, just by observing each other, and we have to remember that people living in close proximity to the natural world, and dependent on it for everything, certainly would be close observers of it and what happens.

Beyond that, I think once wolves became more acclimated to humans, more sociable toward them and reproducing - let us call them dog-wolves - those animals would actually, I believe, go out and hunt with humans. And in that case, the wolf certainly expands the senses of human hunters, both in terms of sight and hearing, whereas the human, with his weapons and fire, increases the power of the wolf enormously.

DAVIES: You know, nothing is cuter than a puppy. Everybody loves dogs - or almost everybody. But I picture our prehistoric ancestors as, you know, kind of living on the edge between starvation and subsistence. And it's maybe a little harder for me to think of them sharing food with any creature they don't have to. To what extent, do you think, was - and I'm asking you to speculate here - but to what extent was affection, as well as just utility, a part of this early association?

DERR: Well, certainly, affection is part. To say something about the hunting and food, it's not clear that early humans were always on the edge of starvation. I doubt, seriously, if they were, except in times of the extreme brutality of the height of the last ice age, and other places where conditions were bad or herds collapsed.

But they were pursuing herds of large animals, remember, and they probably had a fairly steady supply, unless the migrations broke off. There also have been studies that show that small bands of people, of hunters who hunt with dogs, bring home much more meat than those who don't have dogs. So that's the utilitarian side.

The other side is, you're right - puppies, dogs, there's something about them that makes them - we're friends with them. I mean, there are people who dislike dogs, for sure. But dogs also have an uncanny ability - often, if you think about dogs you might know who have walked into a room of visitors to your house, and they have an ability to pick out the one or two who seem to dislike dogs the most, and make friends with them.

DAVIES: To what extent does the archeological record give us evidence that humans and wolves, or dogs, hunted together?

DERR: There have been some finds in recent year - these are, basically, fossils that have been re-examined, in many cases; they were dug up years ago and not sorted through. They now have been re-examined and re-dated. And they are animals, big animals - big dogs is what they are, dog-wolves, that are found in hunting camps. And so there is a supposition that they probably were used in hunting or in - at least, in packing animals and material around, which would greatly extend the reach of the humans.

There are some studies, too, from China about 7,000 years ago, indicating that people were actually raising millet to feed to their hunting dogs, and that this kept the dogs alive during times of thin meat, as it were; times when they weren't - when the game wasn't around, and they weren't getting as much meat as they wanted, they would feed them millet. So that would indicate not only that the early dog was being used as a hunter, but that it was highly valued as a hunter.

DAVIES: So dogs evolved, physically, after they began associating with humans, but they're not simply defined biologically. They're really a cultural creation, too, aren't they?

DERR: They are definitely a cultural creation, and this is one of the reasons that people like to speak of the dog as a separate species from the wolf, even though they're so closely related. But the dog lives with us in a way that wolves don't, and is created by us in different ways so that - in purebred dogs, for example, someone might have an ideal that they're trying to breed for. In other animals, someone might want a companion or a herding dog or a catch dog, which is a dog that will grab livestock or game and hold onto it.

I knew a rancher once, in Central Florida, who had dogs. He had a line of dogs that were famous in ranch country in Florida, and they had been catch dogs. They would go and grab bulls by the nose and hold them while they were branded, or whatever. This...

DAVIES: They would hold bulls by the nose?

DERR: Yeah.

DAVIES: Wow.

DERR: They would grab them on the fleshy part of the face, and it tends to immobilize them. Dogs are nuts, you know. They do crazy things.

DAVIES: But breeding has also given us some pretty odd animals, like the pug. I mean, do you think this is - that some of this breeding has just taken dogs in directions that aren't healthy, aren't good for them?

DERR: You're going to get me in trouble here, but I've been trouble on this score before. Look, I think that some - and I'll say it bluntly, and it has to be said: Some of these breeds are incapable, really, of giving birth without Caesarean section.

You may have seen an article in the Times not too long ago about how some of the brachycephalic dogs - the dogs with the punched-in noses, like the pug or the French bulldog - aren't - airlines will no longer fly them because the animals get up at altitude, and they can't breathe. They die.

Or in hot weather, they can't breathe, and they die. I think that it certainly is wrong to produce animals that aren't healthy. It's bad for the animal. It's bad for the people who love them and take them into their homes, and find out that this dog they love is going to die at a very young age because of some inheritable disease.

Often, these diseases come along with the traits that people are breeding for, in terms of beauty - let's say a nice, blue merle coat and clear blue eyes that they want on a dog. Those may bring conditions like deafness and epilepsy with them. And we really should ask ourselves whether it's fair to the animals to do that. I am of the opinion that it is not.

DAVIES: Well, Mark Derr, it's been interesting. Thanks so much for spending some time with us.

DERR: Thank you.

GROSS: Mark Derr spoke with FRESH AIR contributor Dave Davies. Derr's new book is called "How the Dog Became The Dog - From Wolves To Our Best Friends." I'm Terry Gross, and this is FRESH AIR.

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