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.
History of 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.
- Central Asia: 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.
Curiosity Tamed the Cat: Feline Domestication
In sharp contrast to dogs, cats did not evolve to look or act very different from their wild ancestors. This fact has made it difficult for scientists to determine when exactly cats domesticated. Although evidence shows that cats probably did not evolve from modern large cats, such as lions and tigers, Archaeologists cannot use the shapes of old bones and scientists cannot investigate DNA to distinguish between ancient small wild cats and modern domesticated cats. However, some evidence does lead scientists to believe that the modern domestic cat (Felus catus) may have descended from a European wild cat (Felis silvestris) and an African wild cat (Felis lybica), cats that still exist in the wild.
Other clues provide some convincing evidence about early feline domestication. For example, excavation of a 9,500-year-old gravesite revealed the remains of a human buried alongside a cat. From this evidence, historians believe that most likely by this time humans got personally attached to their feline friends. The proximity of the human and cat indicates that the burial was intentional and that cats held a significant role in that culture.
Even if guessing when cats became domesticated is difficult, why humans took them in is a little easier to speculate. Every kid who's seen a "Tom & Jerry" cartoon is familiar with cats' infamous dislike of mice. Usually cats are more successful at capturing, or at least scaring, their rodent prey than Tom ever was. It's exactly this skill that probably made cats so appealing to humans. Trading pest-control for food and shelter, cats eventually overcame their aversion to domestication.
Cats probably did not take to domestication as easily as wolves/dogs did because cats have no social hierarchy that allows humans to take the alpha role. Wolves travel in packs, following a highest-ranking wolf, but a cat is a solitary and proud animal who takes orders from no one. Although the domestic cat is its own species, its independence and the fact that domestication didn't cause any drastic changes allowed feral cats to survive on their own fairly well even if raised in the luxury of a human home. So, although they are not known for taking orders from humans, perhaps cats stick around because they enjoy receiving food and shelter from their human masters (or servants, depending on who you ask).
Although it was nice to have hunting and pest control partners, humans needed to rely on more than just dogs and cats to advance their civilization. Next, we'll find out how other domesticated animals helped humans progress into transportation and farming.
Beasts of Burden: Domestication of Cattle and Other Livestock
At first, it was obvious that livestock offered early farmers a handy supply of fresh meat and milk. Eventually, people discovered that animals could also assist with farming, and provide fertilizer and new clothing material. Here's a list of some of the major livestock animals that have played significant roles in the history of humanity:
- Cattle: Aurochs, an extinct species, serves as the ancestor of today's tame cattle. In places like the Near East and Africa, people began taming Aurochs. These animals later evolved into the cattle we have today. Perhaps their most important contribution was their use in tilling the land, which expanded farming land and thereby yield significantly.
- Oxen: In a way, the domestication of the ox (around 7000 B.C.) even overshadows the invention of the wheel in its importance to early human civilization. For, without the enormous strength of the ox to pull heavy loads on these wheels, life would have been significantly harder.
- Sheep: Next to dogs, sheep are perhaps the oldest domesticated animal. To take advantage of the wool, people bred wild sheep to lose their kemp (longer hairs) and draw out their wool (inner, shorter hair). It became obvious that herding these animals was only a matter of taking the role of leader in their social hierarchy. Although domestication occurred in the 9000 B.C., weaving wool may not have come around until 4000 B.C. [source: Tomkins].
- Goats: Goats aren't picky eaters, which makes them useful in their ability to survive despite living on dry and infertile land. Poor people who live in areas with few other resources can use the goat for meat, milk and materials like mohair and cashmere [Sherman].
- Pigs: From domestication of the wild boar, humans developed the pig. Having a taste for waste, pigs ate from human trash piles, allowing a primitive trash recycling. And we, in turn, ate pig meat.
Next, we'll take a look at many other animals that provided what was perhaps just as important -- transportation for long distances and heavy loads.
Now We're Going Places: Domestication of Transportation Animals
Before the invention of the steam engine, the automobile, and the airplane, there was the horse-drawn carriage. And although this may seem primitive in comparison to modern transportation, keep in mind that animals allowed for some of the greatest advancements of civilization for millennia through migration and trade. Here are some of the most significant animals that allowed for human transportation:
- Horses: Soil tests have revealed remains of high concentrations of horse manure near ancient settlements to show evidence for domesticated horses 5,600 years ago [source: Lovett]. Also, DNA evidence suggests that today's domesticated horses have origins in many lands and from many different wild herds [source: Briggs]. Although humans probably first used horses for meat and milk, horses became accustomed to pulling carts and humans riding them. Horses allowed humans to go long distances and to travel quickly. Arguably no other animal has contributed as much to human transportation. Eventually, ancient Romans even used them in chariot races. Early horses once lived and then went extinct in North America, only to be reintroduced to the land by the Spanish about 9,000 years later.
- Donkeys: Egyptians tamed donkeys at about the same time horses became domesticated. Although they've fallen out of favor since (evidenced by the pejorative term "ass"), ancient Egyptians revered donkeys. Archeologists have discovered some donkeys who were distinguished with special burial sites, suggesting that the Egyptians considered them highly important and respectable animals [source: Chang].
- Camels: Because Bactrian and Arabian camels can carry large loads and do well with little water, people in desert areas benefitted greatly from domesticating camels. In fact, although people usually associate camels with hot areas, the Bactrian camel has a thick, shaggy coat that even allows it to withstand cold climates. Although at first the domesticated camel was only used for hair, meat and milk, people eventually used the camel for transporting heavy loads over long distances. When this practice came around, it completely replaced the wheel as a transportation tool for a significant period of time in certain areas [source: Meri].
Although livestock and transportation animals provided much-needed labor and helped humans forge civilization, we shouldn't forget about little guys. Next, we'll learn how certain rodents, insects and other animals offered their own contributions through domestication.
The Birds and the Bees: Uses of Other Animals
People have been able to domesticate a variety of other animals that provide numerous other functions for us. These include:
- Chickens & Roosters: Perhaps first domesticated for the entertainment value in cockfighting, roosters and hens didn't produce eggs very frequently until people further domesticated them for this purpose [source: Encyclopedia Britannica].
- Turkeys: American Indians in what is now Mexico probably first domesticated the turkey, and Europe was unfamiliar with the animal until the 16th Century. As one of the few domesticated animals indigenous to America, it makes sense that Americans celebrate Thanksgiving by eating this bird.
- Bees: Before the 19th century, people relied on honey as the main source of sweetness. They got this honey from beehives, and, needless to say, they had to risk multiple stings to attain it. Eventually, people were able to domesticate bees by drawing them in to make their home in rudimentary, man-made beehives. In the 19th century, Lorenzo Lorraine Langstroth significantly advanced the structure of the beehive to allow for more efficient honey production methods.
- Silkworms: Silkworms produce cocoons for the eggs that humans can use to make silk. Historians think the production of silk started in China around 3000 B.C., revealing that people must have begun domesticating the silkworm around this time.
- Rabbits: By the first century B.C., people were using ferrets to flush rabbits out of their homes in the ground. Medieval French monks later domesticated rabbits and raised them for food.
- Hamsters: The origin of domesticated hamsters dates back only to 1930, when a mother and a batch of baby hamsters were caught in Syria. At first, people recognized the value of hamsters in scientific experiments and later as pets. If you know much about the rapid reproduction rate of hamsters, you probably won't be surprised to learn that the whole population of domesticated hamsters derives from this one single family [source: History World].
Some of the animals included in the previous list arguably aren't "domesticated" at all. Authorities in the subject, such as Jared Diamond, use a strict definition of domestication, which only includes animals whose genetic makeup has changed from their ancestors so to allow humans to manipulate their breeding and diet. We can still tame individual animals to do what we need them to do without altering their inheritable nature. For instance, even though Hannibal famously crossed the Alps on elephants, Diamond argues that elephants can only be called tamed because they never formed a whole new species through the domestication process.
Nevertheless, many sources, such as the Encyclopedia Britannica, use a broad definition of domestication to include animals like the ones we've discussed on this page.
For much more information on animals, explore the links on the next page.
Search the least hospitable parts of our planet to discover the resilient world of the tardigrade. Prove how much you know at HowStuffWorks.
More Great Links
- "Dog: Domestication." Encyclopedia Britannica, 2008. (April 3, 2008) http://search.eb.com/eb/article-15457
- "Dogs and More Dogs." NOVA. Feb. 3, 2004. (April 3, 2008) http://www.pbs.org/wgbh/nova/transcripts/3103_dogs.html
- "Domestication." Encyclopedia Britannica. 2008. (April 3, 2008) http://search.eb.com/eb/article-9030865
- "Felis catus." Smithsonian Marine Station at Fort Pierce. (April 7, 2008) http://www.sms.si.edu/IRLspec/Felis_catus.htm
- "History of Domestication of Animals." History World. (April 3, 2008) http://www.historyworld.net/wrldhis/PlainTextHistories.asp?groupid=1813&HistoryID=ab57
- Bard, Kathryn A., Steven Blake Shubert. "Encyclopedia of Ancient Egypt." Routledge, 1999. (April 3, 2008) http://books.google.com/books?id=PG6HffPwmuMC&dq=Encyclopedia+of+the+Archaeology+of+Ancient+Egypt&client=firefox-a&source=gbs_summary_s&cad=0
- Briggs, Helen. "Origins of domestic horse revealed." BBC News. July 16, 2002. (April 3, 2008) http://news.bbc.co.uk/2/hi/science/nature/2129182.stm
- Budiansky, Stephen. "The Covenant of the Wild: Why Animals Chose Domestication: with a New Preface." Yale University Press. 1999. (April 3, 2008) http://books.google.com/books?id=wKO6GFaVpRAC&dq=the+covenant+of+the+wild&client=firefox-a&source=gbs_summary_s&cad=0
- Chang, Kenneth. "Early Egyptians Revered Lowly Donkeys." New York Times. March 25, 2008. (April 3, 2008) http://www.nytimes.com/2008/03/25/science/25donkw.html
- Diamond, Jared. "Evolution, consequences and future of plant and animal domestication." Nature Publishing Group. 2002. (April 3, 2008) http://www.santafe.edu/events/workshops/images/c/c9/Diamond_Nature_02.pdf
- Hanotte et al. "African Pastoralism: Genetic Imprints of Origins and Migrations" Science. April 12, 2002 Vol. 296. no. 5566, pp. 336 - 339.
- Harder, Ben. "Gene Study Traces Cattle Herding in Africa." National Geographic News. April 11, 2002. (April 3, 2008) http://news.nationalgeographic.com/news/2002/04/0411_020411_africacattle.html
- Lovett, Richard A. "Ancient Manure May Be Earliest Proof of Horse Domestication." National Geographic News. Oct. 26, 2006. (April 3, 2008) http://news.nationalgeographic.com/news/2006/10/061026-first-horse.html
- Lowry, Brian. "I Am an Animal: The Story o fIngrid Newkirk and Peta." Daily Variety. Nov. 19, 2007.
- Meri, Josef W., Jere L. Bacharach. "Medieval Islamic Civilization: An Encyclopedia." Taylor & Francis. 2006. (April 3, 2008) http://books.google.com/books?id=H-k9oc9xsuAC&dq=Medieval+Islamic+Civilization:+An+Encyclopedia
- Owen, James. "Egyptian Animals Were Mummified Same Way as Humans." National Geographic News. Sept. 15, 2008. (April 3, 2008) http://news.nationalgeographic.com/news/pf/25388441.html
- Pickrell, John. "Oldest Known Pet Cat? 9,500-Year-Old Burial Found on Cyrus." Naional Geographic News. April 8, 2004. (April 3, 2008) http://news.nationalgeographic.com/news/2004/04/0408_040408_oldestpetcat.html
- Rudik, SK. "Contribution to the history of the horse domestication and breeding in the Ukraine." Hist Med Vet. 2003;28(2):41-6. (April 3, 2008)http://www.ncbi.nlm.nih.gov/pubmed/12838987
- Sherman, David M. "Tending Animals in the Global Village: A Guide to International Veterinary Medicine." Blackwell Publishing, 2002. (April 3, 2008) http://books.google.com/books?id=ax_lLPG634AC&dq=Tending+Animals+in+the+Global+Village
- Tomkins, Stephen. "The Origin of Humankind." Cambridge University Press. 1998. (April 3, 2008) http://books.google.com/books?id=QfBKN2PVfnUC&dq=The+Origins+of+Humankind+tomkins&source=gbs_summary_s&cad=0
- Wade, Nicholas. "From Wolf to Dog, Yes, but When?" New York Times. Nov. 22, 2002. (April 3, 2008) http://query.nytimes.com/gst/fullpage.html?res=9F03EEDE1239F931A15752C1A9649C8B63&sec=&spon=&pagewanted=print