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Posts Tagged ‘sheep’

I’ve written several posts about dog domestication and how the foundation of modern Western “breed” dogs has distorted our ability to figure out where dogs originated.  For several  years, it was strongly contended that dogs were derived from East Asian wolves and that there was only a single domestication event. Most of this studies that point to East Asia as the place of origin have used either mitochondrial DNA and–most recently– y-chromosome analyses. However, a study that examined the largest part of the genome of dogs and wolves found that most domestic dogs share genetic markers with Middle Eastern wolves.  And of course, the oldest of all dog remains are found in a region that runs from Central Asia to Belgium– the earliest, in the Altai Mountains of Siberia, dates to 33,000 years before present.

How can these different findings be reconciled?  I think the best way is simply that dogs were domesticated over a long process that involved several different populations of wolves.  Mark Derr in How the Dog Became the Dog lays out a very complex scenario in which humans and wolves associated with each other over tens of thousands of years.  For most of this time wolves living near humans had little morphological differences from wolves not associated with humans, but then, during the Last Glacial Maximum, the wolves associating with humans began to develop the morphological traits associated with domestication. These same forces created a general gracilization in humans, and they likely had the same effects on the wolves that were living with and relying upon humans for sustenance.  The shortened muzzle trait, which has been found in several specimens that are over 30,000 years old, is perhaps the earliest trait to have developed in the wolves that became dogs. Derr posits that the region running from the Carpathians to Central Asia would have been where the first anatomically distinct dogs would have been found– and that is precisely where the oldest dog remains to date were found. (The manuscript for How the Dog Became the Dog was submitted months before this discovery was published.)

For whatever reason, the dogs that descend from Middle Eastern wolves wound up contributing the most to modern dog lineages, though there is some influence of East Asian wolves in East Asian dog breeds, just as many Scandinavian dog breeds also descend from the a mitochondrial DNA matriline that originated in a European wolf bitch. When wolves were more common, they exchanged genes with dogs and the wolves that became dogs– and vice versa.

All of these issues are very complex and are often contradictory. And they are further exacerbated with a real methodological problem that exist in most genetic assays of domestic dogs:  they tend to include too many Western breed dogs. Western breed dogs are genetically depauperate compared to the village dogs of Asia and Africa, which have both proven to be quite genetically diverse. Because the African dogs are more genetically diverse than those of Asia and also possess Middle Eastern wolf genetic markers,  it is very unlikely that dogs were domesticated in East Asia in a single domestication event.

Now, what if we had a parallel domestication from which we could compare to the domestication process in dogs?

Well, it turns out we do.

Dogs are the oldest domestic animal. There is no debate about it.

However, the question of what the second domestic animal was has always been debated.  The debate is between two species:  the goat and the sheep. Evidence of domestication for these two species occurred from 9,000 to 11,000 years ago. I think the bulk of the evidence suggests that sheep were the earlier of the two species. The first evidence of domestic sheep appears  around 11,000 years ago in the Middle East, which means that sheep domestication predates the large-scale horticultural societies that would develop in the Fertile Crescent by about a 1,000 years.

We’ve known for a while that sheep are pretty genetically diverse even as domesticates, but the extent of that diversity was only recently revealed in a study that was recently released in PLoS Biology. This study examined over49,000 SNP’s in over 2,800 sheep from  74 breeds.

The study found that these sheep breeds had more diversity than most dog breeds. Many sheep breeds have effective populations in excess of 300 individuals.  The various breeds of sheep we have are the result of breeding for just a few traits, and the two most widespread traits, wool and hornlessness in both sexes, are the result of dominant alleles that are easily transmitted across populations. Sheep breeds were largely not created through inbreeding. They were mostly created through selectively breeding from a genetically diverse population. Sheep were likely domesticated over a large range over a relatively long period of time. There was no greater diversity in the Middle Eastern sheep breeds than those from other places, and what’s more, there was a lot of crossbreeding between breeds over the years.

The study is entirely about sheep, but I think it shows a real weakness in the genetic studies I’ve seen in domestic dogs. Most studies on domestic dogs do not fully account for the amount of loss in genetic diversity that exists in breed dogs. However, almost all dogs in the West are either breed dogs or derived from crosses between breeds. It has been calculated that modern breed formation may have taken away over a third of all the genetic diversity in domestic dogs, which are still a pretty genetically diverse population.

They become even more so when non-breed village dogs from Africa and Asia are included in the analysis.  Dogs from these populations actually suggest that dogs were domesticated in the way sheep were. However, because most dogs in the West derive from dogs that were intensely inbred and/or kept in closed registry populations, a lot of dog genetic diversity was squandered.

Sheep also show that breeds can be founded from genetically diverse populations. Inbreeding is not a requirement for breed formation or maintenance. In the oldest dog “breeds,” like the greater tazi landrace, there is still a lot of genetic diversity when the landrace as a whole is considered one breed. However, when one considers these dog to be separate entities, as they typically are in the West,  they don’t have much. These dogs existed for thousands of years with selective breeding from a genetically diverse population, just as domestic sheep breeds have been. But within the Western closed registry framework, they have lost a lot of that diversity.

Dogs were not created by inbreeding wolves. Sheep were not created by inbreeding wild mouflon.  Instead, through domestication, certain traits were selectively bred from animals presenting novel mutations. Inbreeding would fix these novel traits more quickly, but the genetic evidence shows that most of the oldest forms in dogs predate modern breed formation. That is, dogs like sighthounds, mastiffs, and mountain dogs that existed thousands of years ago didn’t appear by inbreeding but through selective breeding from diverse populations.

The intense inbreeding and linebreeding that exists within the closed registry system for most domestic dogs in the West has created a major distortion in our understanding of how dogs were created.  Dogs that exist within those populations are not very representative of dogs throughout their history.  But the dogs of Africa and Asia point to the possibility that was once there.

If sheep breeders can produce wool, milk, and meat animals that have produced so effectively over thousands of years without resorting to using genetically depauperate populations, why can’t dog breeders?

I think the answer lies in two places:  the Victorian blood purity cult that is the modern dog fancy and the traditions of how dogs are bred. Both of these things have almost metaphysical reasons for existing as they do, for both fly in the face of what modern science says about the importance of genetic diversity in maintaining sustainable, healthy populations.

The other problem that exists with dog genetic diversity is that the economics simply don’t work anymore.  When breeds were being founded, they weren’t as different from landraces. Wealthy individuals kept scores of dogs in their breeding programs, so they had large founding populations. Most people can’t do that today, which is one reason why virtually every breed that has been founded after the Second World War and then placed within a closed registry system has had severe health problems. Further, I don’t think most people want to do the intense culling that one must use to use very tight breeding effectively.  In those days, there was a lot of culling of the weak.

Today, we have situations where it is hard to maintain genetically diverse populations in dog breeds. Crossbreeding is not allowed in any of the established registries, and the blood purity cult won’t allow such heresy to go without fatwas. Dogs that are born through crossbreeding may only participate in competitions if they are spayed or neutered, and their genes never contribute to the next populations. There are some exceptions to the blood purity cult, like the Dalmatian backcross project and the use of Central Asian tazis in the UKC saluki. But in general, blood purity is seen as an ideal. Further, many dogs that are purchased from breeders are given spay-neuter contracts, and more and more municipalities are passing mandatory spay and neuter.

All of these factors are pushing dogs into more and more genetically depauperate populations that, over time, will become less healthy– regardless of what sort of culling and “selecting against disease” continues to happen within the system.

Sheep were lucky.  Because almost every sheep that exists today has some practical purpose, there was never a big push to turn them into fancy animals. By the time of the Industrial Revolution, the bulk of dogs in the West were no longer needed for anything, except as sporting animals and objects of conspicuous consumption. And those factors led to the big push to “improve” them through “scientific” breeding, which was often little more than inbreeding or very tight linebreeding.

Perhaps the best juxtaposition of two dogs that can explain what happens when dogs from genetically diverse populations become “improved breeds” can be found in AKC salukis and tazis from Central Asia. Tazis from Central Asia can live into their twenties, but the average lifespan of a Western breed saluki is something in the 11 to 12 year range.

The tazi was developed from a genetically diverse population, while the saluki is a Western cutting off of dogs of that general type into something called a breed.

If dog breeds had been able to continue on as selectively bred from diverse populations in the West, the results would have been different.

For the very simple reason that large predators tend to exist at lower densities than their prey, fewer wolves would have been involved in dog domestication than would wild sheep have been involved in their domestication– at least in the initial stages. However, over time, we could be talking about a large number of wolves working their way into the dog population, so it may have been a wash.

But sheep very clearly show us that we don’t have to inbreed to create and maintain breeds.

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“They are slickery little suckers!”

Lots of discussion about selective breeding in this clip.

“Now, do you typically wipe the poo off the scrotum?”

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I wrote about this in my mara post.

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Maras will raise their babies communally.

However, females will allow only their offspring to nurse.

So you do get tense situations when the guard changes at the crèche.

***

This story reminds me of a documentary on sheep I saw a few years ago.

This Scottish shepherd had a ewe that had given birth to three lambs, but because these were hardy Highland sheep, he didn’t want to nurse a lamb and turn it into a pet.

One of his other ewes had given birth to the usual twins, but one of these twins died shortly after birth. The ewe had nurse the lamb and was bonded to it, but it just died.

Ewes will not nurse lambs that are not their own, so the extra lamb that the other ewe had could not be fostered without some innovation.

The shepherd skinned the dead lamb, and then he dressed the third lamb in its pelt.

The foster ewe thought the third lamb was her baby, and she allowed him to nurse.

The third lamb continued to wear the skin of the deceased for a day or two. By then the third lamb had drank enough of its new mother’s milk to smell right.

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A bunch of clicker trained sheep could put the sheepdogs out of business.

They just come when called.

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I think the other sheep is a Stone sheep.

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Urials are considered to be part of the same species that includes the European mouflon. However, it has a different chromosome number. And the European mouflon is now believed to be a feral domestic sheep.

I got interested in sheep because of a disagreement I had with a particular sermon  that I heard as a young boy.  The elderly Methodist minister said that the reason why sheep and lambs were so revered in the Bible was because they had no wild ancestors. The sheep exists solely as a domestic animal for man to use, just as man exists solely for God’s purposes.

Of course, I was skeptical. I had never heard of a domestic species that had no wild variant. Animals didn’t just appear.

So I began to research it. I didn’t have the internet, but I did have some old encyclopedias and some National Geographic magazines.

And I thought I had seen a show about wild sheep on PBS.  It was Marty Stouffer’s Wild America series, which always popularized the combat of the bighorn rams in its opening sequence. I do remember watching this particular sequence from the series:

Source

(When the Marty Stouffer scandal broke, I refused to believe it. I still have a bit of a soft spot for the show.)

However, no wild sheep could be found in my part of the country, so I really couldn’t point the bighorns as evidence for a wild form of sheep. I later learned that these wild sheep were a different species from domestic sheep, and that North America actually has two species of wild sheep. The bighorns ranged from the mountains of southern British Columbia through to the Mexican states of Chihuahua, Sonora, and Baja California.

Then there are the Dall or thinhorn sheep of northwestern Canada and Alaska.  I was impressed with their white color.  However, I found out that these white Dall sheep are found only in the northernmost part of their range. In the more southerly parts  of their range, the animals are grayish brown. These are called Stone sheep. In between the white and grayish brown populations, there are gray and white ones called Fannin’s sheep. At one time, I remember reading about these sheep as separate species. However, they may not even be clear subspecies. They may be nothing more than color phases of the same animal.

This confusing taxonomy is not unique to this species of North America sheep, as I would later find out.

But I knew that none of these North American sheep could be the ancestors of domestic sheep.

It wasn’t until I saw a particular program on PBS series Nature that I realized what a wild sheep was.

This particular program was about the domestication of sheep and the development of various forms of sheep dog.

The opening sequence featured a wolf hunting a strange-looking animal, which the narrator (George Page) identified as a mouflon. It was a contrived sequence, and neither wolf nor mouflon were ever on screen together.

The sequence was meant to show the wolf in its wild form and the sheep in its wild form. The wolves hunted the  mouflon for food, and the mouflon did everything possible to avoid the wolves.

The point of the sequence was to introduce how sheep dogs worked. In the case of the livestock guardian dogs, the sheep and dogs were nothing at all like the wolves and the mouflon. They were social partners.

In the case of the actual herding dogs, the dogs exhibited predatory behavior, but it was strictly controlled. The dogs, which were all black and white border collies, didn’t bite the sheep at all.

However, there was an exception that was shown. On the St. Kilda Archipelago, there existed a particularly wild sheep that had not been bred to flock.  Because these sheep would just scatter, the shepherds had use their collies very differently. The collies were used to catch the sheep and hold them, which was not all that different from the way that the wolves were hunting the mouflon.

I now realized that the wild sheep was a mouflon.

But was it really the wild ancestor of the domestic sheep?

Well, it turns out that the European mouflon is actually the dingo among sheep. Just as dingoes descended from fully domesticated dogs, mouflon descend from some population of wild Asian sheep. These sheep went wild after been introduced to Europe. They first appeared in Corsica and Sardinia 7,000 years ago, and from there, they began to appear on the European mainland. For a long time, it was believed that the European mouflon was the ancestor of domestic sheep.

But it is actually the other way around. Domestic sheep are the ancestors of the European mouflon.

That is nice to know, but it still doesn’t tell us what the wild ancestor was.

There are some populations of mouflon in Iran. However, no one has found a genetic connection between these mouflon and the domestic sheep.

To make matters even less clear, it turns out that Asian domestic sheep and European domestic sheep have a considerable amount of genetic divergence. That means that domestic sheep could come from two unknown subspecies  of wild sheep. It could also mean that domestic sheep are a hodgepodge of various mouflon subspecies, including some unknown or extinct forms. It could also mean that domestic sheep descend from at least one unknown species that is closely related to the wild mouflon of Iran.

The argali, the urial, and the snow sheep of Siberia are all relatives of the wild sheep. Although the urial is considered the same species as the various forms of mouflon, it has a different chromosome number.  The argali and the snow sheep also have a different number of chromosomes from the mouflon and domestic sheep. In fact, it is sometimes suggested that the snow sheep are the same species as the Dall or thinhorn sheep. (In fact, it is sometimes suggested that bighorns and Dall sheep are the same species! I’m not going that far.)

My question isn’t really answered yet. All we know is that domestic sheep are closely related to some Iranian mouflon. However, these Iranian mouflon aren’t the ancestor. And domestic sheep are not derived from the European mouflon. The European mouflon is a feral sheep.

So maybe the old sermon was right.

But I doubt it.

My bet is that the European mouflon and the domestic sheep are derived from some unknown subspecies of Asian mouflon that has either gone extinct or has been totally absorbed into the domestic sheep. In fact, I wouldn’t be surprised if two of these unknown subspecies were totally absorbed into the domesticated form.

***

Whatever the wild species from which domestic sheep descend, the fact that the sheep is the second animal that man domesticated has always struck me as a little strange.

It seems to me that domesticating the sheep would be much harder than domesticating other animals. All subspecies of mouflon prefer alpine habitats, so if humans were going to domesticate them, our ancestors were going to have to do a lot of work.  Wild sheep have an instinct to run for higher ground when frightened, and because none of these animals flocked, even hunting them for food sounds like a very difficult process. Hunting wild sheep with rifles today is not for the uninitiated. I can only imagine what people living 11,000 years ago would have had to do to catch these animals.

However, these assumptions might be false.

It is often suggested that dogs were necessary for the domestication of the sheep. I do see some merit in this theory. After all, dogs can run uphill faster than we can, and the dogs could be used to drive the sheep into traps or ambushes.

It is also possible that man was able to gain the trust of some bands of wild sheep that were attracted by the salts in our urine. These sheep grew to trust people, who then began to follow the sheep as they traveled up and down the mountains. In the spring, the sheep would go into the alpine meadows in search of the fresh green grass that grow there, but in the winter, the sheep would have to go back down into lower elevations, where the snow did not cover up so much of the forage.  Some people would keep the wild predators off the sheep, and the sheep that learned to tolerate people were better able to survive.

This scenario makes some sense, simply because the original sheep cultures were nomadic pastoralists. Pastoralists live very much like hunter-gatherers. However, they have a constant food source in the form of the animals they are herding. Unlike people who are reliant upon grain agriculture, pastoralists are not bound to a single piece of land.   They simply move their flocks to the better pastures, which means that these people developed a migratory lifestyle.  Pastoralist cultures still exist today, but it is very likely that the first people to keep sheep were entirely caught up in this lifestyle.

There is a certain amount of freedom that goes with this  life. After all, even we modern Americans still romanticize the freedom of that the cowboys of the Old West must have experienced. We even romanticize the various native peoples of the Great Plains who were in a sort of proto-pastoralist relationship with the plains bison. Their lives were without fences. Their lives were tied up in the need for fresh grass and water, for their lives were ultimately tied up in the animals.

This is the freedom that these first sheep-keeping pastoralists would have experienced. Unlike hunter-gatherers who had to be experts in bringing down prey or collecting berries, these people were much more secure. Their main food source was always grazing but a few yards from them. It was combination the security of agriculture and the freedom of the nomad.

Now, I should also note here than no wild sheep has wool like a domestic sheep, and none of these early domestic sheep had this type of wool either. The reason for this is pretty clear.

Have you ever seen a wild poodle?

Poodle hair and sheep wool are not shed. Both grow continuously. A wild animal that has hair that grows continuously is at a disadvantage. Unshorn wool sheep are very uncomfortable with such long wool, and they are also prone to infections and parasites. Just as poodle hair must be trimmed, wool sheep must be shorn.

Because none of the original sheep had wool to shear, the sheep were kept for their meat and hides. They were also kept for their milk.  The first domestic animal milk that humans ever tasted was from a sheep.

Now we don’t often think of sheep as dairy animals, but there are still dairy sheep herds in the United States.

As the first hoof stock that people were keeping, sheep provided a constant source of meat, hides (which could be used to make leather), and milk. Although we could eat dogs and make something out of their pelts, dogs were far too useful for other purposes. Sheep really can’t guard settlements or assist in the hunt. They also produced more meat than dogs ever could.

Man, sheep, and dogs were now joined together, and soon other creatures were to join us. The goat was domesticated not long after the sheep. Then came the pig and then the cow.

Man was figuring out how to tame animals and selectively breed them for his own purposes. The first selective breeding was definitely haphazard. Indeed, the first modern selective breeding did not occur until the middle of the eighteenth century.

But we never would have gotten to that point if we had not started somewhere.

And we started with the wild ancestor the domestic sheep. Whatever that was.

***

I should finally point out that one animal called a wild sheep that could never be considered an ancestor of the domestic sheep is the aoudad or Barbary sheep. It looks superficially like a bighorn sheep with very strangely shaped horns. However, it is not a true sheep at all. It is in its own genus (Ammotragus), while all true sheep are in the genus Ovis.

See earlier post:

I. The Natural and Unnatural History of Sheep

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Sardinian mouflon.

Domestic sheep are not that common in North America. When I write about this species, it is almost as if I am discussing an animal that other peoples in far distant lands keep. Sheep are just not a part of the current American landscape. You can drive for miles down rural roads in virtually any part of the country, and you’ll be very lucky to see a single flock.

And if we look at the raw numbers, it turns out that sheep just aren’t that numerous here.

There are about 6 million sheep in the US. That sounds like a lot, but keep in mind that America is home to over 96 million cattle and over 61 million pigs.  We are not currently a major sheep producing nation.

This was not always the case. Indeed, it was the sheep trails that opened up much of the West for settlers to come pouring in. Their numbers were always relatively high, even with the constant worries of poison plants and predation from wolves, bears, cougars, coyotes, and free roaming domestic dogs. Sheep had high economic value for their wool and meat.

The US sheep population continued to grow until the 1950’s, when it was estimated that 55 million grazed our pastures and open ranges. Then wool prices began to drop. And Americans lost their appetite for lamb and mutton. These meats are not universally palatable, especially when the majority of the population is accustomed to eating chicken, pork, and beef.

Of course, sheep are far from a rare species. The worldwide population is estimated at  over 1 billion. China and Australia have the largest populations. China has nearly 144 million, while Australia has over 99 million.

The US and Canada combined have about 7 million sheep total. We just aren’t sheep people (at least at this point in history).

Like all domesticated animals, sheep have benefited from their relationship with us.  Wild sheep numbers in Eurasia and North America are nothing compared to that 1 billion figure for domestic sheep.  In fact, there are more than twice as many sheep in the world as there are domestic dogs. Current estimates suggest that there are only about 400 million dogs worldwide.

Now, domestic dogs are the oldest of our domesticated species. Estimates for the  date of their domestication range from 12,000 to 135,000 years ago.

However, the sheep is thought to have been the second animal that joined us in this venture. The oldest domestic sheep are thought to date to 11,000 years before present.

Sheep are our oldest hoof stock. This will be the first post in a series about this animal. These posts will explore their domestication and their natural history. They will also examine how domestication has changed the sheep into an animal that is very dependent upon people for its survival.

And because of their long association with us, domestic sheep are as much an enigma as domestic dogs are.

Although it is pretty conclusive that domestic dogs are a form of Canis lupus, this fact is still not universally accepted. It was even less accepted before the advent of sophisticated techniques for the analysis of mitochondrial and nuclear DNA. Charles Darwin believed that wolves, coyotes, and all forms of jackal had something to do with the origin of the domestic dog. Konrad Lorenz wasted a big chunk of Man Meets Dog, describing lupus dogs that were derived from wolves and aureus dogs derived from jackals.

Well, the wild ancestor of the sheep is still not been fully documented. It is believed to have descended from some form of mouflon, but mouflon taxonomy is itself a giant mess. It is possible that several types of mouflon played a role in the domestic sheep, and it is also possible that other species of wild sheep–especially the urial and the argali– may have contributed genes to the domestic sheep.

I hope this introductory post gives you some idea of what to look for in the coming days. I have no idea how long this particular series will go.

The reason why I writing it this way is because I tried to put all of this in one long post last night, and it was far too long.

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