About the same time as the invention of agriculture (c.8000 BC) another revolution occurred: the taming of wild animals for domestic use. As with agriculture, the more settled lifestyle that better hunting and gathering allowed at the end of the last Ice Age was important, because it gave people the time and opportunity to keep and domesticate animals.
However, while animals of many different species have been tamed and kept as pets by humans, only a very few have been big enough (100 pounds or more) to be useful as sources of food and labor while meeting three basic criteria for true domestication. First, they must be herbivorous (plant eaters) and fast growing so they use up a minimum of our food resources and quickly become useful to us as a food source. Herbivores directly convert the plants they eat into meat, while carnivores require at least one extra level (i.e., other animals) in the food chain to survive. Therefore, pound for pound, it will take up to ten times as much plant nutrition to raise and support a carnivore as it does to for an herbivore.
Secondly, animals suitable for domestication should live in herds or packs with a strict social hierarchy of which humans can assume leadership. The third criterion for domestication is that animals must be easy to tame and willing to breed in captivity. This also rules out most carnivores, who are typically aggressive hunters and less easily domesticated than herbivores. An obvious exception is dogs who, being relatively small, must hunt cooperatively in packs, making them more social and easy to domesticate.
As with agricultural plants, what few animal species that are suitable for domestication are found predominantly in Eurasia and especially in what we call the Middle East of the Fertile Crescent. There were five such animals. The first two of these to be domesticated were sheep and goats, largely because they were the most docile and easy to tame. Sheep provided meat, milk, and fur. They also were ruminants, which meant they could digest the cellulose from grass, thus making previously useless land (e.g., rocky hillsides) useful.
As with plants, our ancestors also tampered with natural selection, using selective breeding to produce animals that were fat, meaty, slow, and with long wool rather than fur that is shed seasonally, qualities that are useful for us but normally harmful to a species in the wild. Eventually, this process would produce sheep and goats that differed considerably from their cousins in nature.
The next animal domesticated was the pig (c.7000 BC). Unlike sheep and goats, the pig was not a ruminant and providing no milk or fur. However, pigs did provide meat and, being scavengers, had several advantages. Whether scavenging in the local woods or city streets, they were cheap to keep. They also needed little or no supervision, making them easy to keep compared to flocks of sheep and goats that needed constant shepherding. Finally, until very recently, towns and cities rarely had proper sanitation facilities, making them extremely unclean and unhealthy. Pigs scavenging in the streets helped keep them a little cleaner. In fact, many towns had laws protecting them, despite their mean dispositions and occasional habit of attacking children.
Cattle were next (c.6500 BC), which gave milk, meat, hides, and could eat grass. However, they were bigger, wilder, and tougher to tame than sheep, goats, and pigs, causing some civilizations, such as the Minoans on Crete, to see the bull as a symbol of power. Probably the most innovative use for the cow was to hitch it up to a plow, tapping a non-human energy source that increased the power at our disposal and the amount of land under cultivation many times over. However, the earliest farmers hitched the plow up to the cow's horns, not the most efficient use of its power.
Somewhat later (c.3000 BC), horses were domesticated with three far-reaching effects. First of all, they could be used as a source of labor like cattle although their full potential wouldn’t be tapped until the invention of the horse-collar (c.900 AD) which pulled from the chest rather than the neck. Secondly, mounted warfare made armies much more mobile, dangerous, and destructive. This was especially true of nomadic horsemen who would occasionally be the scourge of richer and more sedentary civilizations. Finally, mounted messengers dramatically quickened communications, making it possible to keep in touch with and rule much larger empires.
Agriculture and domestication of animals created two basic types of lifestyle: settled farmers tending their crops and livestock in the richer farmlands, and nomads wandering with their herds of sheep, goats, and horses across the dry grasslands on the fringes of civilization. As we shall see, these two ways of life, nomads and farmers, have clashed repeatedly throughout history. We shall also see how the infectious diseases domesticated herds of animals carried would play a critical role in Eurasia’s dominance of the planet.