It all started 10 to 20 million years ago when the earliest ancestors of sheep evolved in the mountains of Central Asia. During the last Ice Age, these animals started to move outwards. Some moved west into Europe, others eastward into Siberia and some even moved across the frozen Bering Strait about 750,000 years ago into North America. All modern domestic sheep are descended from the ones that moved west into Europe - the Mouflon. Mouflon were dark-coloured with large horns and shed their coats each year. Our prehistoric ancestors regularly hunted them. Around 11,000 years ago, at a number of discreet locations in an area called the Fertile Crescent (in current-day Middle East) over a relatively short period of time (just 1000 years or so), human hunter-gatherers started to cultivate crops and domesticate animals, including sheep. A number of archeological excavations have shown that, about 10,500 years ago, the human diet changed from essentially eating whatever wild animals were available, including deer, hares, tortoises, fish and some wild sheep, to eating predominantly sheep. Similarly, the excavations show that, as the diet changed, humans shifted from hunting wild sheep to keeping a few sheep tethered up to managing large numbers of sheep in pens. In just 1000 years, sheep changed our diet and came to dominate our ancient villages.
Two waves of sheep came out of the Fertile Crescent. The first wave was domesticated but the sheep didn’t look very different from their wild cousins. Around 7000 years ago, these small, dark, horned sheep moved out and spread across Europe. Isolated remnant populations of these early sheep can still be found on various islands. The St Kilda Archipelago is a remote group of islands off the west coast of Scotland. Sheep were originally taken to these islands by Stone Age people and also the Vikings. Separated from mainland breeds, these sheep bred and developed in isolation, with some isolated groups becoming sufficiently different to become a breed in their own right. Examples include the Soay (from Soay Island) and the Boreray (from Boreray Island). A particularly interesting breed is the North Ronaldsay. It comes from the island of North Ronaldsay, which is the northern-most island of the Orkney group off Scotland. It represents a particularly early stage in the evolution of sheep and the mouflon influence is readily visible. DNA studies have shown them to be closely related to sheep found in Stone Age villages in the Orkneys 3000 years ago. In 1832, a wall was put around the island, confining the sheep to the foreshore. The sheep essentially maintained themselves on seaweed. Only the animals that could survive on this diet persisted. As seaweed is low in copper, this breed is susceptible to copper poisoning when kept under standard sheep management conditions. Another interesting breed is the Manx Loaghtan, which is only found on the Isle of Man. All of these sheep are collectively classed as primitive breeds and retain many of the characteristics of early sheep. They are, in effect, living ovine dinosaurs. Another particularly interesting breed is the Herdwick of Yorkshire. Folklore has it that they are descended from sheep introduced to the UK by the Vikings. Recent genomic sequencing has shown the folklore to be correct. Herdwicks are, in fact, descendents of Viking sheep.
Manx Longtan ram
A second wave of sheep moved out from the Middle East around 5000 years ago. These new sheep had been developed with wool in mind. It was these that helped shape the majority of modern-day breeds. Gradual selection occurred for the animals with the longest fluffiest coats that did not shed. It is not easy to domesticate an animal. How did Neolithic farmers turn wild sheep into docile farm animals that would allow them to be handled and breed in captivity? Jared Diamond, an evolutionary physiologist, has come up with a check list of six traits that animals must have if they are going to pass the “domestication test”. Many animals have some of these traits, a few, including sheep, have all six. These traits are:
The animal can’t be a picky eater.
The animal needs to mature quickly - Farmers don’t want to wait years looking after something before they can eat it or put it to some other use.
The animal must be able to be bred in captivity - Stress or mate preference can stop wild animals breeding.
The animal must be basically docile by nature.
The animal can’t be too panicky - Deer, in comparison to sheep, can die from shock during handling.
The animal needs to have a social structure that includes a strong leader - This allows groups of animals to be controlled, for example, in sheep by a human taking the position of a flock leader in the form of a shepherd. Recent research has shown that shee not only recognize people but can also interpret their facial expressions.
Sheep are also creatures that gain security from familiar environments and routine predictable days. They have a strong sense of place and tend to stick to their home range. Having a sense of place and looking to a leader made for easy domestication. These natural instincts were encouraged over thousands of years during the domestication process. Today these characteristics are particularly apparent in many of the older breeds that have not undergone relatively intense commercial selection, which has occurred over the last 150 years for various physical characteristics. Their behaviours can be particularly seen in some flocks in Africa and the Middle East today. Over the centuries, farmers selected sheep for the characteristics they wanted. These included:
Quiet submissive behavior compared to flighty and aggressive behaviour.
Animals that were not too large and without large horns, which made management difficult.
A white fleece - By 3000BC, the first records of white sheep appeared. White wool was rare and highly prized compared to brown, black and piebald fleeces. A white sheep is far easier to see on a hillside than a dark one and white wool will absorb colored dyes.
No shedding - In the original sheep, like all mammals, the growth of body hair naturally slows during Spring. Eventually this leads to a break in the hair fibre. This, in turn, leads to the coat, which has grown over the previous year, being lost or shed. Initially, the little wool that early sheep had was either plucked or collected from the fields. However, it was possible to select for a genetic mutation where this natural break no longer occurred. This meant that the coat continued to grow, season after season, year after year. This continuously growing coat is made up of three different types of fibre, one of which is wool. Over the centuries, selection occurred for the animals that did not shed, had more wool and for various other wool characteristics. These days, shedding is only found in the primitive breeds and in breeds that have been selected to shed such as the Dorper and Persian.
In a wild situation, this mutation that blocks shedding is harmful. With the coat continuously growing, its physical bulk gradually increases. As this process progresses, it becomes increasing difficult for the animal to defaecate, urinate, breed and eventually eat and even walk. At the same time, the animal becomes increasingly vulnerable to fungal, bacterial and insect infections. Without the intervention of humans removing the fleece by shearing, the animal will die. In this way, wool breeds have become dependent on humans to not only stay well but indeed to survive. Humans have selected this (harmful) gene in order to harvest the coat or fleece. Two extreme examples of non-shedding are Shrek and Chris. Shrek was one of thousands of Merinos at a New Zealand station. Each year, for 6 years, he missed the annual round up by hiding in caves on the property. When eventually shorn in 2004, his fleece weighed 27 kg. Chris was a wild-living Australian merino. When eventually caught and shorn under sedation, his fleece weighed 40 kg. Experts present at the time believed that, had he not been shorn soon, Chris would have expired from carrying so much excess weight in wool. In many parts of the world, however, this genetic mutation has not been selected and sheep continue to shed their “winter coat” annually each Spring before the onset of the hot weather in Summer.
Selection for a whole plethora of characteristics continues, including those involving wool, meat, milk, temperament, mothering ability, resistance to disease, environmental tolerance, growth rates, body shape, etc, etc. Selection for high meat yields has changed the body shape. In many breeds, the body has become longer. Some modern breeds almost look like “ovine dachsunds”. It is interesting to compare modern breeds, such as the Suffolk and Dorper, with the wild mouflon. When born, the body length of a Mouflon lamb relative to its height is only slightly shorter than that of a Suffolk lamb but, by adulthood, the Suffolk has a body approximately 25% longer relative to height. All of this has been achieved through genetic selection. The European Mouflon still survives in pockets of Sardinia, Corsica and Cyprus to this day. The domestication journey from this type of sheep to what we have today has been quite a long one. We have changed sheep but they have changed us, too. We have changed sheep from wild animals into placid manageable animals with characteristics that we wanted. There are now one billion sheep in the world and at least 1000 breeds (with 65 British breeds alone) from huge Dohne Merinos to tiny tough Ouessants. Sheep now live on every continent except Antarctica. Through both intensive and intentional breeding by humans, and by the evolution of various traits by the sheep as they evolved in response to their location, sheep can now be found from the freezing mountain ranges of Alaska to the scorching deserts of the Sudan. Sheep provide us with meat, milk, cheese, lanolin, sheepskin and wool. At the same time, we have changed from hunter-gatherers to the modern beings we are today. It has been quite a journey together.
All photos taken by Dr Colin Walker at the Great Yorkshire Show, Harrowgate, 2019