Horses… goats… evolution

Horses… goats… evolution

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I am not sure if this is the right place for this question, but under the StackExchange umbrella I think its best I ask it here.

After watching shows like Game Of Thrones, Vikings, Spartans etc. I noticed regardless how far back any of these show date, there are always horses and goats. And they are - visually, as we know them today. I understand that when they shoot these shows using horses and goats, is probably convenient.

Considering evolution, under the assumption that all living things have evolved:

  • How long have horses and goats been on earth?

  • If they did not look like they look today, when did they evolve to what they are today?

All these shows (and other works of fiction) go back, at most, around 2,500-3,000 years. Anatomically modern man, so-called homo sapiens sapiens, is usually thought to have arisen around 150,000-200,000 years ago. So from an evolutionary viewpoint, these timeframes are mostly irrelevant - people haven't changed much between early Greek times and the Middle Ages, and neither have other animals. It's just too brief a period for major evolutionary change.

What has happened to animals over that time is domestication - the artificial selection and breeding of animals, which began (according to Wikipedia), around 6000 years ago. I'm not entirely sure what horses looked like back then, though. Genetically they were similar to today's horses, but since we can see huge differences between different horse breeds, even though they're the same species, we can suppose that Spartan horses in the 6th century BC might have been different from horses used by Scandinavians in the 8th century AD.

As for the question of how long they've been on Earth - it's hard to answer. "Horses", of some definition, have been around for millions of years, though only at some point could they be considered identical to today's horses.

And as for why you keep seeing them everywhere, whether in historical accounts, historical fiction or history-inspired fiction is just because they're so useful. Horses were used by any civilization they were introduced to because they are strong, reliable animals for work and transportation. Goats are used for milk and meat and keeping greenery under control. Man domesticated animals for their usefulness, and horses and goats, alongside the rest of the farmhouse gang, are very useful.

The Evolution of Horses

Imagine a world in which horses of all colors, shapes, and sizes roamed the world, some barely larger than a small dog. That world no longer exists--but once it was real. Today's horses represent just one tiny twig on an immense family tree that spans millions of years. All the other branches of the horse family, known as Equidae, are now extinct. The earliest known horses evolved 55 million years ago and for much of this time, multiple horse species lived at the same time, often side by side, as seen in this diorama.

Ancient Horses

Some 10 million years ago, up to a dozen species of horses roamed the Great Plains of North America. These relatives of the modern horse came in many shapes and sizes. Some lived in the forest, while others preferred open grassland.

Here, two large Dinohippus horses can be seen grazing on grass, much like horses today. But unlike modern horses, a three-toed Hypohippus tiptoes through the forest, nibbling on leaves. A small, three-toed Nannippus, shown here eating shrubs, ate both grass and leaves.

In the background are several other large mammals alive at that time, including Procamelus, a camel relative a herd of Dinohippus horses Gomphotherium, a distant relative of true elephants and Teleoceras, a hornless rhinoceros.

A Brief History of Horses

By 55 million years ago, the first members of the horse family, the dog-sized Hyracotherium, were scampering through the forests that covered North America. For more than half their history, most horses remained small, forest browsers. But changing climate conditions allowed grasslands to expand, and about 20 million years ago, many new species rapidly evolved. Some--but not all--became larger and had the familiar hooves and grazing diets that we associate with horses today. Only these species survived to the present, but in the past, small and large species lived side by side.

Changing Sizes

Horses were once much smaller than they are today. But there was not a steady increase in size over time. Little Nannippus, shown in the diorama at full adult size, was actually smaller than its predecessors.


The Dinohippus shown grazing on the left is a close relative of horses today. Like modern-day Equus, Dinohippus had single-toed hooves and ate mostly grass. The other extinct species shown in the diorama had three toes and never developed single hooves.

Our Furry Friends: the History of Animal Domestication

Most of us go about our day without considering our encounters with domesticated animals: our pet dog, the horse we rode on the beach, the cow we just had for lunch. Yet animal domestication has played a significant role in our lives. “The history of domestication is interesting because it changed human history. The domestication of animals was important enough to have happened in many places and for different species rather than just once,” said Kim Worley, Associate Professor in the department of molecular and human genetics at the Baylor College of Medicine. Questions of why, how, and especially when animals became domesticated have intrigued scientists for years.

Although new technology involving mitochondrial DNA has allowed researchers to estimate when animals were first domesticated, there remains some doubt about the precise dating of a timeline. Scientists believe the dog was the first animal to be domesticated, though some believe it may even have been earlier. Since then, numerous animals including horses, pigs, and even honeybees have been domesticated for human purposes—like farming and companionship, among others.

Pet Domestications

The idea that a dog is man’s best friend seems to be a very old concept. In fact, a dog jawbone found in Iraq led scientists to believe that dogs were domesticated over 14,000 years ago. Although wolves are the closest relatives of dogs, scientists are able to distinguish the skeletal elements because wolf heads grow larger through adulthood, whereas that of a dog retains juvenile traits.

Though dogs have been domesticated for a long time, they have undergone many changes since those earliest years, as humans have used selective breeding to create new dog breeds with desired qualities. The Romans preferred colors for their dogs: shepherd’s dogs were bred white so they did not look like wolves at night and farmyard dogs were to be black to scare away thieves. Their shapes have also changed, although smaller-bodied dogs are not a modern invention. There is evidence that a dog similar to the Pekingese, a small, vulnerable dog, lived in China in the 1st century A.D.

Cats are descended from five different types of wildcat, and are thought to have been first domesticated around 7,500 B.C. Whilethey have been used as companions and pets, they have historically also been used for controlling mice and rat infestations. In fact, it is believed that cats may have first encountered humans after they were attracted to rat-infested areas where humans lived.

Though the first evidence of a domesticated cat was found in Cyprus, they are most famous for their role in ancient Egyptian society. Egyptians often mummified cats and placed them in luxurious chambers in the pyramids. There were even three feline goddesses that Egyptians worshipped.

Farm Domestications

Alan K. Outram, head of archaeology at the University of Exeter, says that for most species, studying domestication is not about pets, but about finding the origins of a farming economy that produced food rather than collecting it from the wild. The first animals to be domesticated for food use are thought to be sheep, between 11,000 and 9,000 B.C. in Southwest Asia. Goats followed later around 8,000 BC. Both animals were used for their meat, milk, and coats, and became an integral part of nomadic communities.

Ross Tellam, a researcher at CSIRO Livestock Industries in Brisbane, Australia, said that scientists can tell when milk-bearing animals were domesticated based on when the humans in the area became lactose tolerant. “The mutation that enabled the utilization of lactose as an adult gave an enormous advantage to that population and contributed to stable human populations that had the luxury of excess calories,” Tellam said. “This helped civilizations to emerge.”

Pigs and cattle were domesticated around the same time as sheep and goats, but tended to be domesticated by more settled communities. “Farming vastly increased humans' capacity to feed larger populations, and also led to a much more settled way of life. With the arrival of large permanent settlements, and with the ownership of land and agricultural surplus come major changes in the way societies were organized,” Outram explained. Animals that belonged to farming communities were herded instead of immediately eaten because the farmer’s ability to tame them meant a continuous supply of meat and dairy.

“The history of human civilizations and cattle domestication are intimately intertwined,” Tellam said. “The ability of humans to maintain a reliable, high energy food source that was mobile and able to live on poor quality land was a huge advantage and this factor certainly fostered stable communities and new knowledge.”

Kim Worley believes that understanding cattle domestication is crucial to the well-being of humans. “For cattle, there is great interest in using traits important to meat and milk production, disease resistance, heat tolerance, etc.,” she said. All of these features of cattle are of interest to humans because of how often we eat their meat or drink their milk. It is thus highly important that these products be the healthiest they possibly can be.

It has been hard to pinpoint a place and time that horses were domesticated, since they were widespread and did not take on distinct morphological changes when domesticated, as observed in other animals. “Many domestic animals see a significant size drop upon initial domestication, and some animals show significant morphological change, too. Horse size does not seem to have been affected in the same way as other animals and there are no immediately visible morphological changes,” Outram said.

There have been reports of horse domestication as early as 5,000 B.C. in Kazakhstan and 4,000 B.C. in the Eurasian Steppes, a stretch of land between Hungary and Mongolia. Archaeological evidence suggests that horses were used initially for food and milk—not riding—since the teeth of these very early domesticated horses do not show evidence of being worn down by a bit (the part of the harness that fits in a horse’s mouth). The first conclusive evidence of horse riding, in the form of bit-worn teeth, was found in Kazakhstan and dates back to 3,500-3,000 B.C.

“The riding of horses was a very significant additional development. This led to a revolution in transport, trade, migration, and forms of warfare,” Outram said. “Horseback riding may have been a key component in the fast spread of culturally important ideas and technologies.”

Horses have provided a means of transportation for thousands of years, even beyond horseback riding, as exemplified in the horse-drawn chariots of Mesopotamia in 2,000 B.C. Up until modern times, horses have played a key role in warfare and have provided transportation to the masses.

Unique Domestications

Elephants, unlike other domesticated animals, have never been truly tamed, though it is thought that they were serving humans in India as early as 2,000 B.C. They can be taught many behaviors and may act under the command of humans, but are still known to have outbreaks of temper. Male elephants are harder to control, so females are often used for domestication purposes the exception is elephants trained for war. Besides warfare where they were used for intimidation, elephants have been used to provide transportation for people and goods as well as for entertainment, as in circuses and zoos. Throughout the past few decades, the care of elephants in circuses and zoos has greatly improved, allowing these majestic animals to continue to be semi-domesticated and seen by millions.

Many would not consider honeybees to be a domesticated animal, and while they can be aggressive, humans have found a way to control them. Beekeepers collect honey and beeswax using artificial hives and smokers that protect them from the insects. Honey was a sought-after product in ancient Greece and the Roman Empire, and ancient bee keepers have even been depicted in multiple wall paintings in Egyptian pyramids. However, honeybee domestication could date back further still, to 4,000 B.C., since researchers believe honey bee domestication began with indigenous tribes all over the world that would harvest honey from nests for food.

The Downside to Domestication

Although domesticated animals have brought humans invaluable advantages throughout history, they have not come without a price. One of the main disadvantages of animal domestication has been an increase in the number of diseases from contact with animals. Animal domestication has allowed the human population to increase and create densely populated areas, but at the same time has allowed for the transmission of pathogens from the animals—pathogens which otherwise may have remained isolated. Farm animals have especially put people at risk: cows with tuberculosis, pigs with influenza, and horses with rhinoviruses. Humans can also contract diseases from their pets and even share a few parasites with their furry companions. Even though domesticated animals may cause disease, they played a necessary role in mankind’s history and existence and will continue to play a key part in our civilization.

So why hasn’t man domesticated every animal? After all, a horse and zebra are pretty similar, but you will not see many people trying to ride a zebra. Evolutionary biologist Jared Diamond identified six criteria that an animal must meet in order to domesticate it:

  1. Flexible diet
  2. Reasonably fast growth rate
  3. Ability to breed in captivity
  4. Pleasant disposition
  5. Temperament that makes it unlikely to panic
  6. Modifiable social hierarchy

With these characteristics in mind, it makes sense that a relatively good-natured pig is domesticated while a violent warthog is not. It makes sense why we can’t use a zebra for milk or a squirrel as a circus animal.

This science feature article was written under the guidance of JYI Science Writing Mentor Margaret Harris.

Evolution of the Horse

The evolution of the horse, a mammal of the family Equidae, occurred over a geologic time scale of 50 million years, transforming the small, dog-sized, forest-dwelling Eohippus into the modern horse. Paleozoologists have been able to piece together a more complete outline of the evolutionary lineage of the modern horse than of any other animal.

The horse belongs to the order Perissodactyla (odd-toed ungulates), the members of which all share hooved feet and an odd number of toes on each foot, as well as mobile upper lips and a similar tooth structure. This means that horses share a common ancestry with tapirs and rhinoceroses. The perissodactyls arose in the late Paleocene, less than 10 million years after the Cretaceous–Paleogene extinction event. This group of animals appears to have been originally specialized for life in tropical forests, but whereas tapirs and, to some extent, rhinoceroses, retained their jungle specializations, modern horses are adapted to life on drier land, in the much harsher climatic conditions of the steppes. Other species of Equus are adapted to a variety of intermediate conditions.

The Earliest Horses – Hyracotherium and Mesohippus

Until an even earlier candidate is found, paleontologists agree that the ultimate ancestor of all modern horses was Eohippus, the “dawn horse,” a tiny (no more than 50 pounds), deer-like herbivore with four toes on its front feet and three toes on its back feet. (Eohippus was for many years known as Hyracotherium, a subtle paleontological difference of which the less you know, the better!) The giveaway to Eohippus’ status is its posture: this perissodactyl put most of its weight on a single toe of each foot, anticipating later equine developments. Eohippus was closely related to another early ungulate, Palaeotherium, which occupied a distant side branch of the horse evolutionary tree.

Toward True Horses – Epihippus, Parahippus and Merychippus

During the Miocene epoch, North America saw the evolution of “intermediate” horses, bigger than Hyracotherium and its ilk but smaller than the equines that followed. One of the most important of these was Epihippus (“marginal horse”), which was slightly heavier (possibly weighing a few hundred pounds) and equipped with more robust grinding teeth than its ancestors. As you might have guessed, Epihippus also continued the trend toward enlarged middle toes, and it seems to have been the first prehistoric horse to spend more time feeding in meadows than in forests.

Following Epihippus were two more “hippi,” Parahippus and Merychippus. Parahippus (“almost horse”) can be considered a next-model Miohippus, slightly bigger than its ancestor and (like Epihippus) sporting long legs, robust teeth, and enlarged middle toes. Merychippus (“ruminant horse”) was the largest of all these intermediate equines, about the size of a modern horse (1,000 pounds) and blessed with an especially fast gait.

Next Step, Equus – Hipparion and Hippidion

Following the success of intermediate horses like Parahippus and Merychippus, the stage was set for the emergence of bigger, more robust, more “horsey” horses. Chief among these were the similarly named Hipparion (“like a horse”) and Hippidion (“like a pony”). Hipparion was the most successful horse of its day, radiating out from its North American habitat (by way of the Siberian land bridge) to Africa and Eurasia. Hipparion was about the size of a modern horse only a trained eye would have noticed the two vestigial toes surrounding its single hooves.

Lesser known than Hipparion, but perhaps more interesting, was Hippidion, one of the few prehistoric horses to have colonized South America (where it persisted until historical times). The donkey-sized Hippidion was distinguished by its prominent nasal bones, a clue that it had a highly developed sense of smell. Hippidion may well turn out to have been a species of Equus, making it more closely related to modern horses than Hipparion was.

Some of the most notable prehistoric horses

American Zebra Also known as the Hagerman horse.

Anchitherium A long-lived “side branch” on the equine tree of life.

Dinohippus This prehistoric horse wasn’t quite as fearsome as its name.

Epihippus This tiny, prehistoric horse lived about 30 million years ago.

Eurohippus Scientists have discovered a pregnant specimen of this ancient horse.

Hipparion One of the most successful horses of the Miocene epoch.

Hippidion This donkey-sized horse had a prominent snout.

Hypohippus This Miocene horse had unusually short legs.

Hyracotherium The horse formerly known as Eohippus.

Merychippus An important intermediate step in equine evolution.

Mesohippus This “middle horse” was about the size of a deer.

Miohippus This “Miocene horse” actually lived much earlier.

Orohippus This prehistoric horse was a close relative of Hyracotherium.

Palaeotherium This tapir-like beast was remotely related to modern horses.

Parahippus This “almost horse” had noticeably enlarged middle toes.

Animals and Livestock of Early Plymouth

Kerry cattle, now a historic rare breed, probably represent the breed recorded as "black cows" in early Plymouth Colony.

The Pilgrims did not bring any large livestock animals with them on the Mayflower. In fact, the only animals known with certainty to have come on the Mayflower were two dogs, an English mastiff and an English spaniel, who are mentioned on a couple of occasions in the Pilgrims' journals. Although not specifically mentioned, it seems likely that they had with them some chickens, because chicken broth was given by Mayflower passenger Edward Winslow to the Wampanoag sachem Massasoit when he was sick in early 1623 and it is also likely they brought some pigs. In 1623, Emmanual Altham visited Plymouth and reported there were six goats, fifty pigs, and many chickens.

The first cattle arrived at Plymouth on the ship Anne in 1623, and more arrived on the ship Jacob in 1624. Onboard the Anne in 1623 were three cows, nicknamed the "Great Black Cow", the "Lesser Black Cow", and the "Great White-Backed Cow". By 1627, both the "Lesser Black Cow" and the "Great White-backed Cow" had calves. Onboard the Jacob in 1624 were four black heifers (a heifer is a young female cow that has not yet had a calf.) The four black heifers were nicknamed "Least", "Raghorn", "Blind", and "Smooth-Horned". There was also a "Red Cow" that belonged to the poor of the colony, which had a red female calf around 1625, and a male calf in 1627.

By May 1627, there were 16 head of cattle and at least 22 goats living in Plymouth. The exact arrival of the first sheep in the colony is uncertain, but in January 1628 the Plymouth Court recorded that Myles Standish purchased from Abraham Pierce two shares of the "Red Cow" in exchange for two lambs. And probate estate inventories for three Mayflower passengers made in 1633 (Samuel Fuller, Francis Eaton, and Peter Browne) show that all three men owned several rams, sheep, and lambs. The first horses and oxen did not begin arriving until the 1630s, most being brought to the Massachusetts Bay Colony to the north.

Plymouth colonists Samuel Fuller, Francis Eaton, and Peter Browne (a weaver) are recorded as having owned sheep.

Goats began arriving in Plymouth in 1623.

Chickens were very common in early Plymouth and quite probably were brought on the Mayflower. The Dorking breed, still around today as a historic breed, actually originates from the home parish of Mayflower passengers William Mullins and Peter Browne.

Meet the Relatives

The horse family (Equidae) today is quite small. All horse breeds, from slim thoroughbred racehorses to stocky plow horses to tiny ponies, belong to a single species, Equus caballus. What's more, all surviving branches of the horse family tree are also members of this same genus Equus, which now consists of only seven living species. Other equids include donkeys, asses, and zebras.

The horse (Equus caballus) includes all domesticated horse breeds. Some scientists also consider the Asiatic wild horse, or Przewalski horse, to be a variety of Equus caballus, though it is often called a separate species, Equus przewalskii. Domestic horses are thought to have been bred from the European wild horse, or tarpan, extinct since 1919.

The donkey (Equus asinus) is a domesticated African ass native to eastern Africa.

The onager and kulan are varieties of the Asiatic ass (Equus hemionus), which has five subspecies in the Middle East and Asia.

The kiang (Equus kiang) is an Asian ass with three subspecies ranging from China to India.

The largest zebra, Grevy's zebra (Equus grevyi) of eastern Africa, has the narrowest stripes.

Known for the "gridiron" stripes on its rump, the mountain zebra (Equus zebra) of southern Africa is endangered due to poaching and habitat loss.

Burchell's zebra (Equus burchelli) has wide stripes. It has several subspecies with distinctive patterns.

The quagga, a form of Burchell's zebra that is sometimes considered its own species, disappeared in the mid-1800s. It formerly lived in southeastern Africa.

About Scientific Names

Scientists use scientific names to catalog life--ideally, each true species should have a name different from every other. With very closely related organisms, however, it may be difficult to draw a sharp line between species. While many scientists think that all living horses can be grouped in one species (Equus caballus), agreement is not universal.

Next of Kin

The only surviving branch of the horse family is the genus Equus, which includes zebras, asses, and donkeys along with the horse. But which living animals outside the horse family are the horse's closest relatives? Hint: You won't find them on a farm.

Here's another hint: Follow the feet. Horses belong to a group of mammals with an odd number of toes. That rules out mammals with two toes, or "cloven hooves," like goats, pigs, cows, deer, and camels.

So who are the other odd-toed, plant-eating animals? Most members of this group, known as perissodactyls, are extinct. But several species survive at present. They include rhinoceroses and tapirs, the horse's closest living relatives.

Extinct Relatives

Horses are more closely related to extinct perissodactyls like this brontothere than they are to cows, pigs, and goats.

15 Amazing Things You Probably Didn’t Know About Goats

Goats and humans have a long and productive history together. Over the millennia, we’ve found a range of interesting uses for these incredible animals—which are also capable of some unbelievable feats of their own. To celebrate National Dairy Goat Awareness Week, here are 15 amazing facts about goats.


The great goat domestication took place about 11,000 years ago in the Near East. The event was a pivotal moment in human history that represented a key shift of mankind from hunter-gatherers to agriculture-based societies.


The earliest European settlers of America brought goats over on the Mayflower. By 1630, a Jamestown census listed goats as one of that colony’s most valuable possessions.


The fair was host to the first dairy goat show in America as well as an exhibit featuring 300 Angora goats, the most ever shown at one time. With their heavy coats of curly mohair, the Angoras drew swarms of fans to the Louisiana Purchase Exposition and increased national recognition for the breed.


You may know that a baby goat is called a kid, but did you know that, because of that, a goat giving birth is said to be “kidding”? We’re not … joking.


Instead, they just have a strong dental pad. They do, however, have an incredibly mobile upper lip that helps them to sort through spiny, thorny twigs to find plants’ tender leaves.


This unusual shape, shared by sheep and several other ungulates, gives them a fuller range of vision than humans and other animals with round pupils. Goats can see 320 to 340 degrees in their periphery—everything except for what’s directly behind them—which is useful in avoiding predators. The drawback to the flattened pupil is that goats are unable to look up or down without moving their heads.


The four-chambered stomach helps goats digest tough roughage like grass and hay. Food enters the rumen first and then passes to the honeycombed reticulum where non-digestible objects are separated out. In the omasum chamber, water is removed from the food before it finally enters the “true” stomach, the abomasums.


Even though we drink cow’s milk almost exclusively here in the States, around the globe more people eat and drink meat and milk from goats than any other animal.


It’s naturally homogenized (meaning it doesn’t separate out into layers in its original state) and is easier to digest than cow’s milk, even by people who are lactose intolerant. It’s also higher in calcium and vitamin A.


One of the more remarkable species of goats is the myotonic goat, better known as the fainting goat. Because of a genetic quirk, when they get excited or startled, myotonic goats’ muscles freeze up, causing them to topple over. They’re not actually fainting—they remain totally conscious and their muscles return to normal within minutes or seconds—but the notable behavior has made them Internet favorites.


Among the many pets that populated the White House during Abraham Lincoln’s time in office were two goats, Nanny and Nanko. They were particularly beloved by Lincoln’s son, Tad, who even used them for chariot rides around the White House.


The incredibly soft and expensive cashmere is made of the downy winter undercoat produced by certain goats. The price of cashmere is so high because the hand-wrought process of separating the silky material from the goat’s wiry outer coat is incredibly time-consuming. And, it takes at least two goats to make every sweater.


According to an Ethiopian legend, the stimulating properties of coffee were discovered when a goat herder found his flock frolicking with extra verve after consuming the red berries of the coffee shrub. The plant had the same energizing effect on the herder himself—and with that, the tradition of drinking coffee was (supposedly) born.


Not only can they survive in precarious rocky habitats, they can even climb trees.


Just as human voices will vary in cadence and inflection by geographical region, a particular goat’s bleat will sound different from that of a goat in a different country.

How Animal Domestication Works

In today's world, we take animal domestication for granted. But from meat and dairy products to faithful companionship, domesticated animals have provided us innumerable products, services and hours of labor that have had profound effect on the history of humanity.

At first, humans used animals merely for food. But eventually, we began to catch on that animals can be useful for work, clothes, protection and transportation. In the wild, animals are protective of themselves and suspicious of other animals. But humans have been able to change this behavior. Over time, some animals become gentler and submit to human instruction -- what's called domestication. In this process, an entire animal species evolves to become naturally accustomed to living among and interacting with humans.

It's important to keep in mind that not everyone believes animal domestication is a good thing. The cofounder of People for the Ethical Treatment of Animals (PETA), Ingrid Newkirk, has famously voiced her opposition to human interference in animal lives. This also means that she dislikes the idea of pets in general. And as an "animal abolitionist," she seeks freedom for all captive animals [source: Lowry].

However, others look on the history of animal domestication in a kinder light. The author Stephen Budiansky argues that it is a perfectly natural process that provides advantages to both humans and animals. Budiansky subscribes to the theory that animals actually chose domestication, preferring the reliable comfort of captivity to the harsh wild [source: Budiansky]. He also points out that there are some species that we have, or could have, saved from extinction by domesticating them.

Regardless, no one can deny the enormous contributions that animal domestication has made to the advancement of humankind. Each domesticated species has offered its own spoils and has its own story of domestication, but all domestication happens through roughly the same biological process. Let's take a look at this process. How do humans orchestrate an entire species' transformation from wild to mild?

A Whole Different Animal: How Domestication Happens

How could wild creatures like wolves be ancestors of cute little Pomeranians? To understand, we first need to know how genetics and evolution work. Animal offspring inherit genes from their parents, and these genes indicate what traits the offspring will have. The variety of genes and the possibility of mutation allow for animal species to change, or evolve, over time. In the process of natural selection, the animals with traits that allow them to survive better will be more likely to breed, until very gradually the only members who survive end up inheriting those helpful traits.

In artificial selection, humans choose desirable traits in animals that they want to see in the animal's offspring. For example, if people want bigger horses to pull their loads, they can put the biggest male and the biggest female horses together and encourage them to breed. This increases the chances that the offspring will also be big. Using another big horse to breed with that offspring will continue the process, until finally, after generations of people continue the process on generations of horses, the entire horse species will be bigger. Using the same process, humans can breed animals to be a certain color, furrier, smaller, gentler or stronger, among other things. This is how humans domesticate animals -- so much so that wolves eventually become a different animal, gentle enough to keep in the home. Or, sheep yield more wool. Or, horses let us ride them.

If this is true, then why don't we ever see a pet panda or someone riding a zebra? It turns out that we can't domesticate every animal. Author Jared Diamond writes that humans have succeeded in truly domesticating only 14 animal species out of about 148 candidates [source: Diamond]. He proposes that for humans to domesticate an animal species, the species usually satisfies these criteria:

  • The right diet: Picky eaters have always made life difficult for their mothers, so one can imagine the frustrations involved in keeping up an animal with picky tastes. Because many animals have specific dietary needs and carnivores get expensive to feed, humans can only domesticate animals that thrive on cheap, accessible food.
  • Fast growth rate: The species must grow at a fast rate for herders and farmers to yield a timely return on the investment of raising it.
  • Friendly disposition: Vicious animals by definition don't usually like it when humans attempt to bring them into captivity and won't let humans handle them.
  • Easy breeding: If the animal refuses to breed under the conditions human captors can provide, then obviously, its period under human control is short-lived.
  • Respect a social hierarchy: In the wild, if the animals form social structures in which they all follow a dominant member, then humans can establish themselves as leader-of-the-pack.
  • Won't panic: Many animals freak out when they are restrained, kept in fences or perceive a threat. Cows, on the other hand, remain fairly complaisant and unflappable despite these conditions, making them easier to domesticate.

Pandas and zebras are far too violent and have thwarted human attempts to domesticate them. However, exceptions might come to mind after examining Diamond's list. For instance, isn't the wolf (as predecessor to the dog) vicious and the cat solitary? The stories of dogs and cats are unique ones that we'll learn about a little later.

On the next page, we'll take a look at the long story behind domestication.

Some of our earliest evidence of man (and art) is tied to animals. Cave illustrations depict bison and deer. Obviously, animals have played a large part in the lives of humans throughout our history, becoming integral to our survival, our history and our very identity. It seems natural that we would want to incorporate and include animals in our lives as much as possible for food, companionship, clothing, milk and a slew of other things.

From archeological evidence such as fossils, historians have learned a lot about man's domestication of animals. Animal domestication is partly tied to human domestication, or the human shift from hunter-gatherer to farmer. Though hunter-gatherers worked with domesticated dogs long before human domestication, later on, farmers saw the benefit of keeping livestock. As some people became farmers and started to settle in one place, raising domesticated livestock offered them the convenience of fresh meat as well as manure for fertilizing crops. Diamond points out that the civilizations that domesticated animals (and plants) consequently wielded more power and were able to spread their cultures and languages [source: Diamond].

Civilizations all over the ancient world domesticated animals for various reasons, depending on which animals were around them and what the animals could provide humans. Certain animals even took on religious significance in many civilizations, such as Ancient Egypt and Rome. Here is a breakdown of where animals were originally domesticated:

  • Southwest Asia: This area probably included some of the first domesticated dogs, sheep, goats and pigs.
  • CentralAsia: People raised chicken and used Bactrian camels for carrying loads in Central Asia.
  • Arabia: As the name implies, the Arabian camel (a one-humped camel, also known as a dromedary) originated here.
  • China: China was home to early domestication of the water buffalo, pigs and dogs.
  • Ukraine: People in the area that is now Ukraine domesticated the wild tarpan horses that historians believe are the ancestors of modern horses [source: Rudik].
  • Egypt: The donkey came in handy here, as it can work hard without much water and vegetation.
  • South America: The domesticated llama and alpaca came from this continent. Historians believe South Americans saved these species from the brink of extinction with domestication [source: History World].

From what experts have learned about the progress of animal domestication, as a species becomes more domesticated, it changes. For example, domesticated animals' brains may become smaller and their sensory abilities less precise [source: Diamond]. Presumably, these changes occur because the animal doesn't need the same level of intelligence and sharp senses of sight and hearing for survival in a domesticated home. Other common changes include floppy ears, curly hair and especially changes in size and mating habits. Domesticated animals are more likely to mate year-round, rather than seasonally, as they do in the wild [source: Encyclopedia Britannica]. These changes and others often cause domesticated animals to look drastically different from their wild ancestors.

Humans themselves have changed significantly as a result of animal domestication. For example, milk has changed our digestive system. Before animal domestication, people naturally developed lactose intolerance as they grew into adulthood (and no longer needed a mother's breast milk). That is not always the case anymore. When humans started raising livestock, they started drinking more milk, and this has adapted our digestive systems to accommodate milk throughout our lives.

Next, we'll learn how the legendary evolution of the dog may have produced man's earliest and most faithful animal companion.

The Beginning of a Beautiful Friendship: Canine Domestication

How a wolf could transform from suspicious, wild beast to obedient, cuddly Fido may seem mystifying or even unbelievable. But scientists have used DNA evidence to show that, more than likely, the dog did indeed descend from the gray wolf.

Although the oldest fossils of a domesticated dog are from a 14,000-year-old dog grave, DNA evidence suggests dogs diverged from wolves much earlier than that (with estimates ranging from 15,000 to more than 100,000 years ago) [source: Wade]. Regardless, historians agree that humans domesticated dogs before any other animal -- making dog man's oldest friend, if not his best.

Scientists can only guess how dogs and humans first became friendly. A popular theory suggests that humans began taking in wolf pups and eventually were able to tame them. Another theory proposes that the tamest wolves were not afraid to rummage through human trash sites to find food. Because they fed this way, these tamer wolves were more likely to survive and evolved into dogs through natural selection [source: NOVA].

Because wolves operate in packs, humans easily took the place of the "highest ranking wolf." So the animals quickly learned obedience. As tamer wolves were more likely to stick around humans, evolution naturally (or humans intentionally) bred tamer and tamer wolves, until eventually, we got the dog. Sometime during this process, man and tamed wolf realized they made for a dynamic duo on the hunting scene. A combination of human ingenuity and wolf speed and ferocity, this pair shared the rewards of their captured game in a mutually beneficial relationship.

However, this evolution of wolf to dog still begs the question: Why do dogs look and act so much different from wolves? A 20th century Russian Geneticist, Dmitri Belyaev, was able to solve part of the mystery surrounding how a wolf made such a drastic transformation. In his attempts to breed tame foxes, Belyaev found that after several generations of selective breeding, foxes not only became tamer (which he expected) but also began to take on dog-like characteristics.

Though DNA evidence tells us that wolves, not foxes, are the forefathers of dogs, this experiment uncovered surprising revelations about how behavior and appearance could have changed wolves into dogs [source: NOVA]. As the foxes became tamer, so also did they develop floppy ears, short snouts, spotted coats, highly-set tails and even a tendency to bark. Amazingly, many of these characteristics are absent in wild foxes, much as they are in wolves, so neither artificial nor natural selection could intentionally draw them out. Instead, genes that account for tameness must also carry a code for such things as floppy ears.

Belyaev's findings also help us understand how different dog breeds ended up looking so different from each other when wolves look relatively uniform. Tameness brought about variation unseen in wild wolves, and humans embraced this variation. Smaller cuddly dogs are better at keeping your lap warm, while bigger, faster dogs are better at hunting. Instead of choosing one or the other, humans bred different dogs for different purposes. In the 19th century we saw a surge in the number of dog breeds along with the advent of dog shows.

Now that we have learned about the domestication of dogs, we'll find out how cats clawed their way into our hearts and homes.

In ancient Egypt, dogs were a beloved and revered pet. Some evidence shows that only royalty could own purebred dogs. Some of these lucky dogs donned jeweled collars and enjoyed the comfort of personal servants. Archaeologists have found mummified dogs in the tombs of owners. [source: Encyclopedia Britannica]

10 Farm Animal Hybrids You Didn’t Know Existed

Forget ligers, tigrons and grolar bears (oh my). Plenty of jaw-dropping hybrids can be had at the farm, where cross-species hybrids are more common than you might think.

Image courtesy of Old Hickory Beefalo Farm

1. Beefalo

Ah yes, how fondly we remember the 1970s. A time of afros, Nixon, and of course, the peak of America’s interest in beefalo. English settlers in the American south noticed genetic mixes between American Bison and domestic cattle as far back as 1749, but it would be 100 years until the first intentional hybrids and more than two hundred until beefalo entered the mainstream of American culture. That decade, a peak 6,000 ranchers agreed to raise the fertile hybrid.

Popularity in beefalo has waned since, but the meat still has its fans. Just last year, the American Royal Steak Competition rated a beefalo steak from Merril Cattle Co. as the best in the country for the second year in a row.

2. Dzo

Dzo are the Tibetan cross between yaks and cattle. Like mules, the male version of the hybrid is infertile, but female dzo, or dzomo, are fertile, allowing for the “back breeding” of three-quarter mixes. The hybrids are larger and stronger than the yaks and cattle of the region, making them ideal pack animals for hauling gear to the base of Mount Everest.

3. Zubron

We will move on from the cattle hybrids in a second, but we must mention the zubron: a cross between cows and wisent. Oh, and what’s a wisent, wiseguy? Those are European woods bison that once bordered on extinction, but now are on their way to a comeback thanks to reintroduction efforts. So basically, zubron are Europe’s answer to beefalo.

After WWI, many Europeans thought zubron would replace domestic cattle because of their durability and resistance to disease. But scientists didn’t breed the first fertile zubron until 1960, and in 1980 the Polish government discontinued the program because of a lack of interest from state-owned farms. A single herd of Zubron remain in Bialowieski National Park in Poland.

Image courtesy of Craig Wright/Flickr

4. Cama

Exactly who authorized the crossbreeding of a camel and a llama to create the first cama, and then named it Rama? Oh right: the Crown Prince of Dubai.

Camels weigh six times as much as llamas, so suffice it to say that artificial insemination was the only option for researchers in the United Arab Emirates. They succeeded in 1998, creating an animal they hoped would have the wool of a llama with the even temperament of a camel. Rama, to their disappointment, has proven rather moody.

Image courtesy of the University of Alberta Libraries

5. Yakalo

Alberta is apparently the only home where yakalo — the cross of yaks and buffalo — have ever roamed.

A 1926 edition of the Lyon County Reporter describes the successful cross at Wainwright National Park, one of the Canadian national parks created to maintain the population of American Bison (it was later turned into a military base following WWII). The animals reportedly made for great meat and shrugged off the Canadian winters, but for some reason never caught on.

Image via The Daily Mail/Flickr

6. Sheep Goat

Millions of years of evolutionary separation and a mismatched number of chromosomes wasn’t enough to stop one goat at farm in Northern Germany. He jumped a fence for a romantic encounter with a sheep. Usually, such cross-breeding result in nothing or a stillborn, but farmer Klaus Exsternbrink watched his sheep give birth to a perfectly healthy geep named Lisa, pictured above. (You could say shoat, but the word already denotes a baby pig.)

While natural sheep/goat hybrids are extremely rare, scientists have perfected a technique to create them in a lab. More on that in a bit.

Image courtesy of Whitelands Farms

7. Iron Age Pigs

Iron Age pigs are an ancient farm animal with a modern appeal. Scientist bred a male wild boar with a Tamworth sow to create pigs resembling ancient paintings, with one unintended consequence: the meat was delicious. The animal’s meat is now a common sight at specialty meat markets across around the world.

Image courtesy of Blue Hill Farms

8. Game Bird Hybrids

Birds have a much easier time crossing species lines than mammals, making avian hybrids much more common than mammalian hybrids. Some notable combinations include pheasants and chickens, pheasants and turkeys, and Canada geese mating with just about every other type of geese. Strangely, no one has been able to successfully breed a chicken and a turkey.

9. Mules and Hinnies

The most common and most practical of all hybrids are mules (the offspring of a male donkey and a female horse) and hinnies (the offspring of a male horse and a female donkey). Ever since George Washington brought mule breeding to America (you read that right), mules have played a primary labor role as work animals and pack animals for their superior strength and endurance over horses. And while they can’t be bred, they can be cloned. In 2003, The University of Idaho succeeded creating the first clone of a hybrid animal — a mule named Idaho Gem.

10. Chimeras

Strangely enough, there are two ways to create combinations of sheep and goats. The first is the old-fashioned farm mishap, as described as a geep. The other is to mix up the embryos of each animal in a bioengineering lab. The result is a chimera – an animal made of two genetically distinct cells.

Because they have cells tied to each species, sheep/goat chimeras look like sewn together franken pets. The first such chimera in 1985 broke open a world of scientific possibilities, allowing researchers to do such things as insert human cells in animals (like testing human livers cells in mice). Bioethicists remain highly concerned about chimeras, despite their medical potential. Not only does the practice discount the welfare of animals, but some chimeras could become so human that they’d have to be considered as such.

A tough note to end on for a light-hearted listicle, but something to think about. Scroll back up to that sleeping zubron and look at it for a while if you feel the need.

The Surprising History of America's Wild Horses

Modern horses, zebras, and asses belong to the genus Equus, the only surviving genus in a once diverse family, the Equidae. Based on fossil records, the genus appears to have originated in North America about 4 million years ago and spread to Eurasia (presumably by crossing the Bering land bridge) 2 to 3 million years ago. Following that original emigration, there were additional westward migrations to Asia and return migrations back to North America, as well as several extinctions of Equus species in North America.

The last prehistoric North American horses died out between 13,000 and 11,000 years ago, at the end of the Pleistocene, but by then Equus had spread to Asia, Europe, and Africa.

Animals that on paleontological grounds could be recognized as subspecies of the modern horse originated in North America between 1 million and 2 million years ago. When Linnaeus coined the species name, E. caballus, however, he only had the domesticated animal in mind. Its closest wild ancestor may have been the tarpan, often classified as E. ferus there is no evidence, though, that the tarpan was a different species. In any case the domesticated horse probably did not arise at a single place and time, but was bred from several wild varieties by Eurasian herders.

In recent years, molecular biology has provided new tools for working out the relationships among species and subspecies of equids. For example, based on mutation rates for mitochondrial DNA (mtDNA) Ann Forstén, of the Zoological Institute at the University of Helsinki, has estimated that E. caballus originated approximately 1.7 million years ago in North America. More to the point is her analysis of E. lambei, the Yukon horse, which was the most recent Equus species in North America prior to the horse's disappearance from the continent. Her examination of E. lambei mtDNA (preserved in the Alaskan permafrost) has revealed that the species is genetically equivalent to E. caballus. That conclusion has been further supported by Michael Hofreiter, of the Department of Evolutionary Genetics at the Max Planck Institute in Leipzig, Germany, who has found that the variation fell within that of modern horses.

These recent findings have an unexpected implication. It is well known that domesticated horses were introduced into North America beginning with the Spanish conquest, and that escaped horses subsequently spread throughout the American Great Plains. Customarily, such wild horses that survive today are designated "feral" and regarded as intrusive, exotic animals, unlike the native horses that died out at the end of the Pleistocene. But as E. caballus, they are not so alien after all. The fact that horses were domesticated before they were reintroduced matters little from a biological viewpoint. Indeed, domestication altered them little, as we can see by how quickly horses revert to ancient behavioral patterns in the wild.

Consider this parallel. To all intents and purposes, the Mongolian wild horse (E. przewalskii, or E. caballus przewalskii) disappeared from its habitat in Mongolia and northern China a hundred years ago. It survived only in zoos and reserves. That is not domestication in the classic sense, but it is captivity, with keepers providing food and veterinarians providing health care. Then surplus animals were released during the 1990s and now repopulate a portion of their native range in Mongolia and China. Are they a reintroduced native species or not? And how does their claim to endemism differ from that of E. caballus in North America, except for the length and degree of captivity?

The wild horse in the United States is generally labeled non-native by most federal and state agencies dealing with wildlife management, whose legal mandate is usually to protect native wildlife and prevent non-native species from having ecologically harmful effects. But the two key elements for defining an animal as a native species are where it originated and whether or not it coevolved with its habitat. E. caballus can lay claim to doing both in North America. So a good argument can be made that it, too, should enjoy protection as a form of native wildlife.

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