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Posts Tagged ‘origin of the domestic dog’

Changes in diet lead to changes in morphology and behavior:

Source.

These are precisely the same changes that have happened between wild and domestic Canis lupus populations.

Domestic variants are called Canis lupus familiaris.

In the same way that these lizards have evolved to eat vegetation, domestic dogs have new digestive adaptations to consume carbohydrates.

But these does not mean that new species have been created.

In the case of dogs and wolves, there has continued to be a small but not insignificant gene flow between wild and domestic populations. Black wolves in North America obtain their melanism from a mutation that was introduced into their population through breeding with domestic dogs, and now melanistic Italian wolves have been found to have exactly the same mutation that was also introduced in exactly the same way.

I don’t think dogs and wolves will ever become divergent enough to become distinct species, but I do think that smaller dogs, which are genetically isolated from the larger ones, could eventually evolve into a new species.

If there is no gene flow between the lizards on these two islands, they will also eventually become so genetically distinct as to lose chemical infertility.

I should also note that Dawkins hits the nail right on the head when he makes the caveat that we should not automatically assume that the lizards of Pod Kopiste haven’t also experienced rapid evolution as the ones on Pod Mrcaru. They could have indeed experienced similar rapid evolution, but the two would have derived from a common ancestor.

I think some of the problems in doing comparison research on dogs and wolves is that people are unwilling or unable to understand that this possibility exists.

There is an assumption that the wolves we are studying in captive situations are truly reflective of the ancestral population that gave rise to domestic dogs.

Most of these wolves are large wolves from northern Eurasia or northern North America.

It’s very unlikely that any of these wolves has contributed much genetic material to  modern dog populations.  North American wolves haven’t contributed much at all.

Further, most wolves in captivity descend from ancestors that were heavily persecuted by man.

What we’ve done is something like the Belyaev experiment in reverse. Whereas Belyaev selected for lack of fear in foxes, man has selected for something akin to paranoia in wolves.

We’ve trapped and poisoned them across the northern hemisphere.

The only ones that have survived, with the exception of some populations in the high arctic, have been those that have been most overly cautious. It’s well-known that many wolves won’t even cross highways, which stymies their recolonization of much of their former range, and in Yellowstone, at least one “Casanova wolf,” a bachelor wolf that mated only with the non pair-bonded wolves in established packs, used the highway as a buffer zone to keep from being killed by the main breeding male  in the pack.

The wolf that once ranged over the northern hemisphere couldn’t be like these animals. It had to have been much more adaptable and less timorous than these very reactive and fearful animals.

The ancient wolf had to have been an animal that was very easy to domesticate.

I’ve occasionally stolen from an insurance company’s advertisements when I’ve written about these issues, but I do think that dog domestication had to have been so easy a caveman could do it.

Modern wolves, in general, are difficult animals to tame. There are exceptions, and I’ve written about them at length on this blog.

But they are exceptions.

And just because some modern wolves have proven to be quite like dogs when socialized to humans doesn’t mean they are all appropriate pets.

It just means that the analogy that says dogs and wolves are as different as chimps and humans is false one.

You’ll never find a chimp that can do all the things that a human can do, but occasionally, you’ll find a wolf that is as tractable as any retriever or a dog that is as obstinate and reactive as any wolf.

Because some wolves are quite like dogs when they are imprinted and socialized with humans, I think it’s actually much more important to tell people not to keep them as pets.

Just because one tame wolf is as nice as a golden retriever doesn’t mean they all are. In fact, most are not.

But it’s not like the difference between humans and chimps.

It’s really the difference between wild and domestic.

I don’t know why it is that with this one domestic species very intelligent species spend hour after hour trying to deny the proper classification with its wild ancestor.

It’s almost creationist in a way.

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I should also note the wall lizards have been introduced to southwestern Ohio. One of the members of the Lazarus department store family introduced a few lizards to the Cincinnati suburbs from Italy, and the wall lizards have expanded their range into adjacent Kentucky and Indiana.

Because they were introduced by a member of the Lazarus family, they are called “Lazarus lizards.”

I wonder if these lizards have any unique adaptations that separate them from the ones in Italy.

 

 

 

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Altai dog

Arguments over dog origins generally fall into two categories:

Where?  And when?

Where and when has the attendant question of “How?”

In the late 90’s and the early part of this century, almost everyone believed that dogs were derived from midden scavengers in the Neolithic.

Towards the middle part of the first decade of the twenty-first century, Savolainen’s big mitochondrial DNA studies came out and suggested that dogs were domesticated in East Asia, eventually refined to southeastern China.

In the middle of the 1990’s, Robert  Wayne’s early mitochondrial DNA analysis put the date of dog domestication so far back that virtually no one accepted it. His research suggested dogs were derived from at least four domestication events, but that the domestication happened 135,000 years ago.

Such an early date was universally poo-pooed.

Many became very heavily wedded to the Neolithic scavenger hypothesis and the attendant domestication= neoteny hypothesis, which has never been properly evaluated with proper scientific scrutiny. In this scenario, wolves scavenged out of the trash heaps of the Neolithic, there was a selection pressure for tameness.

And that was necessary for dogs to evolve from wolves. They had to live on a less nutritious diet, so their brains and jaws got smaller. Dogs are nothing more than neotenic wolves that evolved to live on garbage.

Now, this hypothesis is still quite popular.

But it’s got several problems, not the least of which is that many animals, including many species of wild dog, scavenge off of people, but they have not become tame, neotenic, or smaller brained as  result of it.

And never mind that many claims about brain size and dog domestication result from improper comparisons between domestic dogs and larger brained northern wolves. When compared with the southern wolves from which dogs most likely derive, many improved Western breeds actually have brains that are the same size as those wolves.

And never mind that there are wolves that have been tamed and used as working animals. Historical records of which can be found all over this blog with a simple query into the search function.

Of course, historical research is actually outside the purview of most biologists, so they continue to operate in this paradigm.

Mark Derr recently took to task a recent article by Brian Hare and Vanessa Woods that tried to posit that man and the wolf were constantly at war with each other and that the only way dogs could have ever been domesticated is through scavenging.

The truth is this entire domestication paradigm depends upon dogs being domesticated relatively late, for only during the development of agriculture would there have been enough resources in trash heaps to feed enough scavenging wolves that could then evolve into dogs.

In the first decade of this century, this hypothesis seemed plausible. All the paleontologists and archaeologists who had studied dogs found them to be no later than the Neolithic, except for a few strange dogs, like the now famous dog from the Bonn-Oberkassel site that dated to 14,000 year ago.

When I was first exploring dog domestication, this animal was sometimes treated as evidence that dogs were domesticated in Germany, which as a German-American had me somewhat enthralled, or as an anomaly. 14,000 years ago, Germany was not yet in the Neolithic culture. It was still a land of hunter-gatherers, so it suggested that dogs were domesticated before Neolithic agriculture and the corresponding sedentary life style became commonplace.

For most of the early part of this century, the Natufian culture of the Levant and the peoples living in southeastern China a few thousand years before were deemed to the first people with dogs. The Natufian culture sites, which date from 10,000 to 13,000 years ago, are full of dog remains, and these remains particularly influenced Raymond Coppinger, the prominent exponent of the neoteny=domestication hypothesis.

Now as that first decade of this century drew to a close, there were some findings that were beginning to challenge this entire paradigm.

The first of these was the discovery of an anomalous wolf skull from Goyet Cave in Belgium. This skull was initially documented in the nineteenth century, but a 2008 study that included that skull revealed that was actually much more similar to that of a domestic dog. The skull was dated to 31,700 years ago, but when its mtDNA was examine, it was found not to be related to any living wolf or dog. None of the European wolves that were dated to that time period in that study were related to living wolves or dogs (at least in terms of their mtDNA).

Many researchers simply chalked up the Goyet Cave  “dog” to another anomalous wolf.

Then, in 2011, another dog-like skull was found found in Razboinichya Cave in the Altai Mountains of Russia.  It was dated to 33,000 years ago. This animal was deemed an “incipient dog,” which the researchers believed was just an early attempt at dog domestication which then had to be abandoned when the last glacial maximum forced humans to give up keeping pets.

Of course, this finding came out at about the same time Mark Derr’s How the Dog Became the Dog came out. Derr’s book was the first really cogent critique of the neoteny=domestication hypothesis, and it also tried to tie together all the various bits of genetic and archaeological and paleontological data into a coherent synthesis. In the book, Derr pointed to a recent genome-wide analysis that had suggested that the Middle East wast he primary source for most modern dogs, but he also posited that Central Asia would be the place where one would find the most morphologically distinct dogs. Derr contends that the Middle Eastern wolves followed humans out of the Middle East into Central Asia, where they mixed with those tamed wolves belonging to people from other parts of the world. Here, tame wolves were exchanging genes with each other and were not regularly incorporating the genes of wild wolves, and over time, this population of wolves began to look more distinct.

In case you hadn’t noticed, the Altai Mountains are in Central Asia, and when I sent a link to the study to Mark Derr, he was quite excited.

But the main paradigm suggested that this animal was nothing more than a relic of an early attempt at domestication.

Until this week.

That’s because ta portion of the Razboinichya Cave dog’s DNA was examined and compared to that of dogs and wolves, including 35 prehistoric New World canids.

It found that the  Razboinichya Cave dog was actually more closely related to the pre-Columbian and modern domestic dogs.

So this animal actually was a very early domestic dog.

In Mark Derr’s analysis of the study, he points out that the dog was not related to the wolves living in that part of Central Asia, which means that it may have derived from wolves that were brought there by people.

It does not negate the finding that the bulk of modern domestic dog genetic diversity comes from the Middle East, but it does provide evidence that the place where dogs began to become distinct from wolves was in Central Asia.

But it also shows that dogs were domesticated long before the Neolithic.

The dog is a product of the ancient hunter-gatherer societies of Eurasia.

It is not a creature that evolved on the scrap heap.

It is one that evolved with hunting-gathering man,  most likely participating in the hunt, hauling huge slabs of meat, and guarding camp sites from all sorts of fell beasts.

This ancient dog from the Altai Mountains is the oldest domestic animal on record.

Humans and dogs have been at it a long time.

It’s only now that we have proof it’s been this long.

 

 

 

 

 

 

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wolf dog

Nearly a year ago, I wrote about the discovery of a canine skull in the Goyet Cave in Belgium. This skull had the distinctive features of a dog skull, but  when it was dated, it was found to be 31,700 years old. The next oldest accepted dog remains date to 14,000 years ago and were found in Russia.

The current research on the DNA of domestic dogs suggests that they are 16,000 years old anddescend from a southern Chinese population of wolves. (Another study suggests that this finding may be incorrect.)

So how do we reconcile these two contradictory pieces of evidence?

Well, the real problem is that we currently have a clearly defined idea of what a wolf is and what a dog is. However, it is very likely that this definition is a relatively recent phenomenon in the history of our species. I had an interesting discussion on this post, which was about rather unusual relationship among the Native Americans of the Great Plains, wolves, and domestic dogs. In this hunting society, the defining line between dog and wolf was rather nebulous. (I think they could tell the difference between the two, because the dogs didn’t hunt bison. These wolves were well-known for hunting bison, which is why they are called “Buffalo wolves.” And yes, they still exist.)

When you read the study on the Goyet wolves and dogs and those from Russia and the Ukraine, you notice how genetically diverse the wolf population originally was. It is very likely that there were some wolves that had developed some doggish traits, probably through a semi-domesticated relationship, like the account of the wolves and the Beothuk.

One problem with accepting the Goyet canine as a dog is that there is a huge gap between that dog skull and the next oldest dog remains. A gap has been created, and it doesn’t fit well with the other studies. It violates the scientific principle of parsimony, and thus, it is not yet universally accepted as a dog.

The reason why dogs appear to disappear from the archeological record is that dogs were domesticated several times throughout history.  Because humans were not established as we are now, the conditions that allowed them to keep or have a relationship with “dogs” may have disappeared, and the dogs were forced to return to their ancestral form.

Now, I don’t doubt that this aspect may have led to the disappearance of “dogs” from the archeological record.

However, I think something else might have been at work here. Until Stanley Olsen began examining  the remains of dogs at archeological sites, dog remains were simply thrown away. They weren’t worth studying, and it was nearly impossible for Olsen to get a grant to study dogs in archeological sites.

Because archeology wasn’t interested in these dogs, we don’t have much of a record of them. Who knows what interesting dog or wolf remains have been lost?

I think the Goyet Cave “dog” is a very important find. More research has to be done.

I also think we need to be very careful of the findings that suggest a definite Chinese origin of the domestic dog. It is possible that there were European and East Asian populations of domestic dogs, and the East Asian population wound up replacing the European one, at least through its matriline. (The Savolainien studies are MtDNA studies and are studies of maternal inheritance.) It is also possible that we still don’t have the foggiest clue about where dogs originated because the assumptions do not take into account the diversity of original wolf populations and the fact that the oldest populations of wolves are also from Asia.

But I’m no longer going to parrot the line that we know where dogs come from. It’s all up in the air now. My educated guess is that they are towards the older end of the spectrum, and dogs and wolves have exchanged genes too much for us to pinpoint the exact place for that domestication.

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I’m going to do a post on the dog featured at the top of the post. He has a very interesting story.

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