Department of Agriculture Animal Breeding, Genetics, and Genomics http://www.csrees.usda.gov/ animalbreedinggeneticsgenomics.cfm See also: Animal domestication; Animals as a medi-cal res
Trang 1and to a large extent the characteristics or traits
exhib-ited Different forms of genes, referred to as alleles,
are responsible for the individuality of living things
Some characteristics are determined by alleles of
one gene—for instance, the absence of horns or the
occurrence of a metabolic disease In such cases a
sin-gle mutation can lead to a deleterious condition
However, most traits of significance involve alleles
of more than one gene Superior characteristics for
growth rate or milk yield, so-called polygenic traits,
re-sult from the combination of alleles of many genes
Animal breeding seeks to improve genetically the
fu-ture population of a particular species by increasing
the proportion of desirable alleles or the appropriate
combination of such alleles Genetic improvement
re-quires selection of appropriate breeding animals and
a mating plan for such animals
Selection and Mating Systems Selection is the process of determining which animals are to be used as breeding stock The simplest form
of selection considers only traits of the individual, whereas more complex selection takes account of ad-ditional information on relatives, such as siblings, par-ents, and offspring The accuracy of predicting ge-netic progress is improved by considering relatives This process requires reliable measures for desired traits, acquisition of records from numerous animals, and analysis of the records, which has been aided
by advances in statistical theory and computational
Since the 1940’s, dairy cows in the United States, such as these in Sacramento, California, have been intensively bred for milk production, which has tripled since that time (Photo courtesy of USDA NRCS)
Trang 2power The result is a ranking of animals based on
their genetic merit for single or multiple traits
Several systems have been used for mating selected
animals One involves complementarity, whereby
in-dividuals with high genetic merit for different traits
are mated It has been used to improve livestock in
de-veloping countries by mating animals adapted to local
conditions with highly productive ones from
devel-oped countries The beef cattle, swine, and poultry
in-dustries make heavy use of crossbreeding, in which
animals from different breeds are mated One of its
advantages is the “hybrid vigor” that results Another
system is mating the best to the best One of its hazards
is inbreeding, or the mating of relatives, which often
results in decreased fertility and viability
Environmental Factors
Performance or productivity is determined not only
by genetics but also by environmental factors
Cli-mate, nutrition, and management can affect the
ex-tent to which the genetic poex-tential of an animal is
real-ized Because the productivity of an animal can be
affected deleteriously by heat and disease, climate
and other environmental factors can influence
ani-mals’ performance Similarly, the management
sys-tem used, whether intensive or extensive, can also
af-fect productivity Accordingly, the most productive
animal under one set of conditions may not
necessar-ily be the most productive under another
Interac-tions between genetics and the environment must be
considered in animal breeding
Post-1940’s Developments
Beginning in the mid-twentieth century,
reproduc-tive technologies, most notably artificial
insemina-tion, contributed to rapid improvement in animal
performance These technologies permit animals with
the best genetics to be used widely, resulting in
nu-merous offspring from which to select the best
breed-ing stock for the next generation As a result of
inten-sive selection and management in the United States
beginning in the 1940’s, milk production per cow has
more than tripled The growth rate of chickens has
more than doubled, as has egg production Such
increases have occurred concurrently with a higher
efficiency in raising animals for human food
Molecular biology and biotechnology hold the
po-tential to alter animal breeding processes significantly
in the early twenty-first century Further
understand-ing of the genomes of livestock species should permit
identification of specific genes that will increase the productivity of these animals One approach, known
as marker-assisted selection, would use genetic mark-ers associated with desirable production characteris-tics to enhance genetic improvement If such markers prove to be accurate predictors, they will allow selec-tion of desirable animals long before performance records are available Transfer of desirable genes, within or between species, may also expedite the gen-eration of superior animals The goal of animal breed-ing can be expected to remain similar to that of the past—namely the improvement of animal species to better meet human needs—but the precise nature of the improvements desired and the methodologies used to achieve them could be vastly different
James L Robinson
Further Reading
Bourdon, Richard M Understanding Animal Breeding.
2d ed Upper Saddle River, N.J.: Prentice Hall, 2000
Falconer, D S., and Trudy F C Mackay Introduction to
Quantitative Genetics 4th ed New York: Longman,
1996
Field, Thomas G., and Robert E Taylor Scientific Farm
Animal Production: An Introduction to Animal Science.
9th ed Upper Saddle River, N.J.: Prentice Hall, 2008
Sandøe, Peter, and Stine B Christiansen Ethics of
Ani-mal Use Oxford, England: Blackwell, 2008.
Schatten, Heide, and Gheorghe M Constantinescu,
eds Comparative Reproductive Biology Ames, Iowa:
Blackwell, 2007
Van der Werf, Julius, Hans-Ulrich Graser, Richard
Frankham, and Cedric Gondro, eds Adaptation
and Fitness in Animal Populations: Evolutionary and Breeding Perspectives on Genetic Resource Management.
London: Springer, 2009
Weaver, Robert F., and Philip W Hedrick Genetics 3d
ed Dubuque, Iowa: W C Brown, 1997
Web Site U.S Department of Agriculture Animal Breeding, Genetics, and Genomics http://www.csrees.usda.gov/
animalbreedinggeneticsgenomics.cfm See also: Animal domestication; Animals as a medi-cal resource; Biotechnology; Livestock and animal husbandry
Trang 3Animal domestication
Category: Plant and animal resources
The domestication of animals began long before
re-corded history and has been integral to the
develop-ment of human societies Domesticated species are
re-newable resources that provide humans with food,
fiber, fuel, power, implements, and other benefits.
Background
Domestication is the process of bringing a species
un-der control of humans and gradually changing it
through careful selection, mating, and handling so
that it is more useful Domestication of plants and
ani-mals led to the development of agriculture,
permit-ting people to abandon a hunter-gatherer existence
Instead of following available game and edible wild
plants, people were able to establish permanent
set-tlements Agriculture gave them more time to
de-velop other skills and arts, eventually leading to
com-plex societies and civilizations
A critical aspect of domesticating animals is
direct-ing breeddirect-ing toward a specific function Although
taming is probably a first step, domestication is more
than accustoming animals to the presence of people
Domestication does not apply to captive wild animals
in zoos or circuses, for example; although humans
control such animals and their breeding, the latter is
not directed toward a useful goal (although one could
argue that breeding in captivity helps propagate the
animal and perhaps helps maintain genetic diversity)
Wild animals are those that have not been
domesti-cated, and feral animals are previously domesticated
animals that are no longer under human control
Wild relatives of domesticated species are relatively
easily domesticated, and feral animals can be readily
redomesticated
Characteristics That Favor Domestication
In 1865, the English naturalist Francis Galton
sug-gested the following six physiological and behavioral
characteristics that make some animals good
candi-dates for domestication: hardiness, “dominance”
so-cial behavior, herd behavior, utility to humans, facile
reproduction, and facile husbandry First, hardiness
refers to the ability of the young to tolerate removal
from the mother and the presence of humans The
guinea pig is perhaps an extreme example of
tolerat-ing removal from its mother; it is born ready to eat solid food Most mammals, on the other hand, de-pend on their dams’ milk Primates are poor subjects for domestication because of their helplessness at birth and their relatively long dependence on their mothers for food and nurturing
Second, dominance social behavior, in contrast to territorial behavior, refers to one animal assuming leadership, with the rest of the group acquiescing to
it In domestication, humans co-opt the function of the leader, and animals remain submissive even as adults Third, herd animals are contrasted to those that are solitary or disperse in response to danger Domesticated animals are penned or otherwise re-stricted at various times If they remain together in herds, they are easier to manage Fourth, utility to hu-mans includes their use for food, fiber, traction, com-panionship, and even worship Humans would not make the effort to domesticate an animal unless it had some perceived value However, the purpose for do-mestication may change with time It is likely that the initial motivation for domesticating cattle was for wor-ship—to capture the strength and aura of these ani-mals, which were revered Traction became a subse-quent goal, while contemporary utility in Western societies involves meat and milk production
The fifth characteristic is facile reproduction un-der confined conditions: Animals with finicky repro-ductive behavior and/or elaborate courtship rituals make poor candidates for domestication Sixth, facile husbandry refers to placid behavior and versatility in terms of nutrition Poor candidates for domestication are those animals that are very high strung or depen-dent on a unique feedstuff Koalas, which eat leaves from only certain eucalyptus trees, are poor candi-dates for domestication On the other hand, pigs and goats are excellent candidates because they are not fastidious in their eating habits These six characteris-tics, enunciated more than a century ago, apply strongly to livestock species and somewhat less well to dogs and cats; some argue that cats are not so much domesticated as they are tolerant of humans
History of Animal Domestication Evidence from archaeology suggests that agriculture developed at least ten thousand years ago, after the last ice age That agricultural development occurred
at that point, when the climate was warmer and more stable than it had been, was probably not coincidence Predictability of the weather is particularly crucial for
Trang 4plant agriculture Plant and animal domestication
ap-parently developed together, suggesting a synergy
be-tween the two
Domestication of any animal did not occur at once,
but rather over a substantial period of time, perhaps
hundreds of years Accordingly, the dates for
domesti-cation have a substantial margin of error Further,
they may be modified as new information becomes
available For some species, domestication occurred
independently at more than one location In the
be-ginning, the process may have been almost
acciden-tal, as by raising a captured young animal after its
mother had been killed and observing its behavior
and its responses to various treatments The
domesti-cation of an animal then spread from the site of origin
through trade or war
Animal domestication occurred in various parts of
the world The Middle East, the so-called Fertile
Cres-cent, stretching from Palestine to southern Turkey
and down the valley of the Tigris and Euphrates rivers, was an important site There sheep, goats, cattle, and pigs were domesticated by around 8000 b.p The In-dian subcontinent and east Asia were independent sites for domesticating cattle and pigs, respectively Llamas, alpacas, and guinea pigs were domesticated
in the Andes Mountains of South America Domesti-cation of cats occurred in Egypt, and rabbits were mesticated in Europe No native animal has been do-mesticated in Australia, with the possible exception of the emu Interestingly, few successful domestications occurred after 1000 b.p
Archaeology, coupled with the natural history of domesticated animals and their wild relatives, has been essential in reconstructing the history of domes-tication Examining the skeletal remains at archaeo-logical sites for changes in morphology and distribu-tions by age and sex has helped researchers deduce the extent of domestication Lately, traditional ar-chaeology has been supplemented by the methods of molecular biology Examining extant breeds for their degrees of genetic relationship has been particularly useful in distinguishing single versus dual sites of do-mestication
Early Domesticates: Dogs and Reindeer
Dogs (Canis familiaris) were the earliest known
do-mesticated animals They were widespread across the Northern Hemisphere before other animals were
do-mesticated They derive from wolves (Canis lupus),
with whom they are completely interfertile The earli-est known dog is in a burial site in northern Iraq that dates from 12,000 to 14,000 b.p Other sites, dating from 9000 to 12,000 b.p., have been documented in England, Palestine, Japan, and Idaho While the origi-nal domestication may have occurred in China (the Chinese wolf has some of the detailed physical fea-tures of domesticated dogs), domestication probably occurred at a number of separate sites Domesticated dogs accompanied the American Indians when they occupied the Americas in several waves prior to the end of the last ice age Dingoes were brought to Aus-tralia by trade from Asia long after the Aborigines set-tled Australia 40,000 years ago While dogs were con-sidered a food animal, they have long been known as companions and guards Subsequently, they were de-veloped for hunting and herding
Reindeer (Rangifer tarandus) were another early
domesticate, dating from around 14,000 b.p in north-ern Scandinavia and Russia Herding reindeer
contin-Sheep were one of the first animals to be domesticated (USDA)
Trang 5ues as a principal occupation of the Laplanders of
Fin-land, Sweden, and Norway Reindeer are used to pull
loads and for clothing and shelter (skins), tools
(ant-lers), and food (meat and milk) They are well suited
to their environment and, contrary to other
domesti-cated animals, their range has not been extended by
domestication Attempts to establish reindeer
indus-tries in Canada and Alaska have not been successful
In contrast, the farming of several other deer species
(such as Cervus dama and Cervus elaphus) has recently
gained in importance in New Zealand and Western
Europe They are raised for meat (venison) and
“vel-vet,” the new growth of antlers, which is the basis for
traditional medicines in Asia
Sheep, Pigs, and Cattle
Sheep (Ovis aries) were the first of the common food
animals to be domesticated They were derived from
wild sheep (Ovis orientalis) and were first
domesti-cated in the western Fertile Crescent around 9000 b.p
Goats (Capra hircus), derived from Persian wild goats
(Capra aegarus), were domesticated in the central
Fer-tile Crescent slightly later, 8000-9000 b.p Sheep and
goats have been used for food, skins, and, in the case
of sheep, wool Both were later selected for milk
pro-duction
Pigs (Sus domesticus) probably originated at two
sep-arate sites, the central Fertile Crescent around 8000
b.p and in eastern Asia around 7000 b.p Derived
from wild pigs, they were primarily raised for meat
Despite Islamic and Judaic restrictions against eating pork, it has long been the principal meat consumed in the world The most populous country, China, has ap-proximately 50 percent of the world’s pigs
Cattle (Bos taurus and Bos indicus) are derived from now-extinct wild cattle (aurochs, Bos primigenius) that
ranged over much of Europe and Asia They were probably domesticated independently at two loca-tions, the western Fertile Crescent around 8000 b.p
for Bos taurus and the Indian subcontinent around
7000 b.p for Bos indicus Initially, the animals were
worshiped and used in religious ceremonies Rever-ence for cattle is still practiced by Hindus in India Subsequently, cattle were developed for draft (pulling loads), meat, and milk Their hides are made into leather Traditional cattle in Africa are derived from
initial importations of Bos taurus and subsequent im-portations of male Bos indicus.
Other Domesticated Animals
Asiatic buffaloes (Bubalus bubalus) were domesticated
as the water buffalo in India (5000 b.p.) and as the swamp buffalo in Southeast Asia and southern China (4000 b.p.) While both were developed as draft ani-mals, the water buffalo has also been selected as a dairy animal In 2008, almost 60 percent of the milk production in India was from buffaloes In spite of its tropical origin, the Asiatic buffalo is not very heat tol-erant and compensates by wallowing in water or mud
Neither the African buffalo (Syncerus caffer) nor the
Eight Major Domesticated Animal Species Worldwide
Ruminants
Cattle 1,355 India, Brazil, China, United States, Argentina Meat, milk, hides
Sheep 1,081 China, Australia, India, Iran Wool, meat, milk, hides
Nonruminants
Chickens 16,740 China, United States, Indonesia, Brazil Meat, eggs, feathers
Turkeys 280 United States, France, Italy, Chile Meat, eggs, feathers
Source: Data from Thomas G Field and Robert E Taylor, Scientific Farm Animal Production, 9th ed., 2008.
Trang 6American buffalo (more properly, bison, Bison bison)
have been domesticated Yaks (Bos [Poephagus]
grun-niens) were domesticated at an unknown time in Tibet
or surrounding areas, where they are used as pack
ani-mals and as sources of milk, hair, and hides
Horses (Equus caballus) originated from wild
horses in the Caucasus Mountains around 6000 b.p
Originally used for food and skins, they were also
de-veloped for draft and, much later, for riding Because
they arrived in the Middle East after the development
of written language, their arrival is documented in
writing, so scholars do not need to rely only on the
ar-chaeological record Donkeys (Equus asinus) were
do-mesticated in the Middle East or Northern Africa
(5000 b.p.) They are used as pack animals and for
rid-ing, as is the mule, an infertile cross between a horse
and donkey
Llamas (Lama glama) and alpacas (Lama pacos)
were domesticated in Peru by Incas around 6000 b.p
Llamas are from wild guanaco and alpaca from wild
vicuña, found at higher elevations Llamas are used as
pack animals, alpacas are valued for their fine wool,
and both serve as sources of meat Camels, the
one-humped dromedary (Camelus dromedarius) and
two-humped Bactrian (Camelus bactrianus), were
domesti-cated in Arabia (4000 b.p.) and Central Asia (3500
b.p.), respectively Both are pack animals, and the
dromedary is also used for meat
The largest animal to be domesticated, at 4.5
met-ric tons, was the Asian elephant (Elephas maximus); the
African elephant has not been domesticated
Domes-ticated elephants have been used for draft and riding
for more than 2,000 years In 2007, Asian elephants
numbered less than 40,000 and were approaching
en-dangered status A substantial fraction were working
elephants Burma (also known as Myanmar) alone
had 5,700 working elephants, primarily used for
selec-tive logging of teak forests They drag logs weighing
more than a metric ton, making use of trails, rather
than the roads needed by mechanized log skidders
Elephants are less destructive of the environment
than mechanized equipment However, because
ele-phants are susceptible to heat stroke, they can work
only during the cooler parts of the day (early morning
and late afternoon) and not at all during the hottest
three months of the year Thus, they are not as
effi-cient as mechanical equipment Nevertheless, the
survival of Asian elephants may depend on their
con-tinued use as working elephants
Guinea pigs (Cavia porcellus) were domesticated in
Peru around 5000 b.p They continue to be used as a meat animal in parts of South America Rabbits
(Oryctlagus cuniculus) were domesticated between 600
and 1000 c.e in France They are primarily raised for meat and fur, with Angora rabbits producing a valued wool
Cats (Felis catus) are the animals least changed,
morphologically, by domestication In addition, they are quite capable of surviving without human inter-vention Their domestication occurred relatively late, around 4000 b.p., in Egypt, the home of the African
wild cat (Felis catus libyca), which is difficult to
distin-guish from domestic tabby cats The early Egyptians adopted cats enthusiastically, deifying them and pro-hibiting their export After conversion to Christianity, Egyptians ceased worshiping cats, which were carried
to all parts of the Roman Empire and thence to the rest of the world Cats have been used for companions and for rodent pest control
Chickens (Gallus gallus), along with turkeys (from
North America), ducks and geese, ostriches (from Af-rica), and emus (from Australia), are nonmammals that have been domesticated Chickens were probably derived from wild Red Junglefowl in Southeast Asia before 4,000 b.p Cockfighting was an initial purpose for their domestication The fowls acquired religious significance and were also used for meat and feathers Their selection for egg production has been a rela-tively recent development
Two insects have also been domesticated: honey-bees and silkworms Honeyhoney-bees were domesticated shortly after the last ice age and were the principal source of dietary sweetener until two hundred years ago Also valuable were their wax and venom, the lat-ter used for medicinal purposes One of ten varieties
of silk-producing insects, silkworms were domesti-cated around 5000 b.p in China, producing fiber used in apparel
Utility of Domesticated Animals
As noted in the foregoing section, domesticated ani-mals provide for various basic human needs: food, shelter, clothing, fuel, and emotional well-being Clearly, their predominant use has been as a source of food in the form of meat, milk, and eggs As omni-vores, humans included animal products in their diets long before they domesticated animals Animal prod-ucts are good sources of high-quality protein, miner-als, and vitamins, particularly vitamin B12, which is not available in plant materials Humans have an appetite
Trang 7for foods of animal origin, and as economic
circum-stances permit, the consumption of animal foods
in-creases
Domesticated animals have long provided shelter
and clothing from their hides, hair, wool, and
feath-ers Their bones, horns, and antlers have been used as
implements Animal tissues and blood were the
origi-nal sources of many pharmaceuticals that are now
manufactured For example, before the development
of synthetic insulin, porcine (pig) insulin was
pro-vided to diabetics Animal hearts, kidneys, and livers
have been transplanted into humans Although these
transplants are eventually rejected by the human body,
it seems possible that the development of transgenic
pigs with human tissue factors could provide a source
of permanent transplantable organs Animals are also
used as research subjects, for testing new devices and
drugs before they are applied to humans Although
such uses of animals have become somewhat
contro-versial, much of the development of modern
medi-cine has depended on domesticated animals and on
laboratory animals maintained expressly for research,
primarily rats and mice
The wastes generated by animals are used to
fertil-ize crops They also provide fuel; dried manure is
burned for warmth and to cook food in many
coun-tries of the developing world The development of
biogas generators, in which animal wastes are
con-verted to methane gas, is a more efficient way to
gen-erate fuel It has the added advantage that the residue
can be used as fertilizer for crops
Domesticated animals provide power to cultivate
crops, pull carts or carry loads, lift water, and skid
logs In the last decades of the twentieth century, use
of draft animals increased around the world This
slightly reduced the need for petroleum
Neverthe-less, a return to heavy use of animal power is unlikely
Domesticated animals also serve as insurance and
bank, particularly in developing countries, areas
sub-ject to drought, flooding, and pests, and where
infla-tion is rampant In some areas, animals are the
cur-rency of exchange Animals are used as a walking
larder, especially when refrigeration and other means
of preserving food are unavailable Because storage of
crops for more than a year is difficult and results in
large losses, having animals may buffer a bad crop
year Risk management favors more small animals
over fewer large animals, although this may not be
most efficient from a resource management
perspec-tive; minimizing risk also favors a variety over
similar-ity of animals Until other forms of insurance and banking are fully reliable, animals will continue to be used to alleviate risk
Finally, animals contribute to human well-being by providing companionship and recreation Animals such as dogs and cats are companions to humans, pro-viding emotional support particularly important for the young, elderly, and infirm The use of animal com-panions to promote recovery from illness has been demonstrated to be effective Guide dogs contribute
to an independent lifestyle for blind persons, and monkeys have been trained to provide help to para-plegics and quadripara-plegics Animals also provide recre-ation for humans, as in the form of rodeos, polo playing, riding, backpacking, and racing Noncon-sumptive uses of animals for companionship and rec-reation make definitive contributions to the quality of human life
Numbers of Domesticated Animals
In the early twenty-first century, according to the
ninth edition of Scientific Farm Animal Production
(2008), by Thomas G Field and Robert E Taylor, world estimates for the major domesticated animal species were 16.7 billion chickens, 1.4 billion cattle, 1.1 billion sheep, 1 billion pigs, 0.8 billion goats, 1 bil-lion ducks, 280 milbil-lion turkeys, 174 milbil-lion buffaloes,
55 million horses, 41 million donkeys, 19 million camels, and 12 million mules (For comparison, hu-man beings number about 7 billion.) Domestication brought these animals under human control and vastly increased their numbers and range Domesti-cated animals represent a renewable resource that contributes substantially to the well-being of humans
James L Robinson
Further Reading
Budiansky, Stephen The Covenant of the Wild: Why
Ani-mals Chose Domestication New York: W Morrow,
1992 Reprint New Haven, Conn.: Yale University Press, 1999
Clutton-Brock, Juliet A Natural History of Domesticated
Mammals 2d ed New York: Cambridge University
Press, Natural History Museum, 1999
Diamond, Jared “Why Is a Cow Like a Pyramid?”
Natu-ral History 104, no 7 (July, 1995): 10.
Field, Thomas G., and Robert E Taylor Scientific Farm
Animal Production: An Introduction to Animal Science.
9th ed Upper Saddle River, N.J.: Prentice Hall, 2008
Trang 8Price, Edward O Animal Domestication and Behavior.
New York: CABI, 2002
Roots, Clive Domestication Westport, Conn.:
Green-wood Press, 2007
Smith, Bruce D The Emergence of Agriculture 1995
Re-print New York: Scientific American Library, 1998
Web Site
Food and Agriculture Organization of the
United Nations
Agricultural Statistics
http://faostat.fao.org/site/573/default.aspx#ancor
See also: Agricultural products; Animal breeding;
Animal power; Animals as a medical resource;
Live-stock and animal husbandry
Animal husbandry See Livestock
and animal husbandry
Animal power
Categories: Energy resources; plant and animal
resources
By using animals’ muscle power for traction and
transport, humans expanded the efficiency of these
processes immensely Animal power, essential for heavy
hauling or rapid travel until the mid-1800’s, remains
important to much of the world’s agriculture.
Background
The dog was the first animal domesticated, tamed and
bred from wolf ancestors Archaeological sites
show-ing this development date back approximately eleven
thousand years in both northern Europe and North
America The first dogs may have helped Stone Age
hunters chase and exhaust game They also may have
pulled snow sleds and hauled loads via travois, as they
did for American Indians in later centuries If dogs
were so employed in this era—and it has not been
proved that they were—these would be the first
inten-tional uses of animal power as an energy resource
Other important tasks using their senses and group
instincts to help humans—tracking, scavenging, and
guarding—probably meant that dogs were seldom kept primarily for their muscle power
The next successfully domesticated animals were sheep, goats, pigs, and cattle This process is shown in remains and artifacts from Jericho that document the origins of agriculture Centuries after grain was first cultivated, people began to keep livestock At first the animals were probably loosely controlled and were seen as “walking meat larders” and occasionally pro-viders of milk, fiber, and leather Once the process was under way, around 8000-7000 b.c.e., people must have experimented with riding and other ways to use the animals in their farming
Of these anciently domesticated species, only cat-tle proved to have the combination of strength and malleability to do useful work under human direc-tion Shifting from a plow pushed by a man or woman
to one pulled by an ox multiplied the traction enor-mously and enabled much more food to be produced with the same investment of human time This was a major step in the ongoing “agricultural revolution” that created a growing population, town life, and a material surplus to support specialized trades Using cattle in the fields also called forth other innovations Harnesses and/or yokes had to be created to control the animals, implements had to become larger, and castration of young male animals had to be practiced
to produce oxen that were both strong and docile Later (sometime around 3000 b.c.e.), the wheel was invented Hitching such animals to wheeled carts and wagons, humans could travel farther and more easily and could move bulkier goods Draft animals (ani-mals used for hauling) thus served not only as a direct resource in agriculture and transportation but also as
a source of synergy, expanding their owners’ geo-graphic and trade horizons and inspiring further inventions
While most of the evidence for this sequence of events exists in the ancient Near East, some of the same steps took place independently, perhaps several times, elsewhere in Eurasia For example, the working cattle native to Asia—water buffaloes and yaks—were bred from wild species different from European do-mestic cattle’s ancestors
Horses and Related Species Horses and their kin, the most versatile of hauling and riding animals, were domesticated later Wild horses roamed much of the world during the last ice age but had become extinct in the Americas by 10,000 b.c.e
Trang 9and rare in Western Europe and the Mediterranean
region about the same time How much this
disap-pearance was due to climate change and how much to
humans’ overhunting is uncertain
Many prehistorians believe that horses were first
tamed and trained for riding north of the Black Sea,
where they survived in large numbers Hence they
were reintroduced into Europe and western Asia,
be-tween 3000 and 2000 b.c.e., by successive invasions of
mounted tribesmen from the central Asian steppes
However, as with much of prehistory, the evidence is
unclear Horses never disappeared completely in
Eu-rope, and they may have been domesticated in several
places from local stock
The donkey or ass, which is native to North Africa,
was brought into use in the same millennium
Don-keys loaded with packs or wearing saddlecloths are
shown in Egyptian friezes from 2500 b.c.e.; they also
appear in early Sumerian and Assyrian records
Horses and asses were already being interbred at this time to produce vigorous offspring, notably the mule, with the traits of both species From then until the end
of the nineteenth century, the equids were the most widely used animals in the world for transporting peo-ple and goods They also became immensely impor-tant in agricultural processes
Because of their gait, asses cannot be ridden at high speeds, but their adaptability to harsh conditions makes them good pack animals and beasts-of-all-trades
on small farms Mules, hybrids from mare mothers and donkey sires, combine the horse’s strength with the ass’s stamina Mules have been known to carry 450 kilograms each, going as far as 80 kilometers between water stops
Horses’ special qualities include speed, herd hier-archical instincts that dispose them to follow human leadership, and relative intelligence Horses have been bred to strengthen various traits: the Arabian and
An Indian family sits atop a cart pulled by two bulls People throughout the world have relied on draft power for centuries (AFP/Getty
Im-ages)
Trang 10the modern thoroughbred for speed; the medieval
war horse and the modern shire and Clydesdale for
strength and stamina; the Shetland pony for multiple
tasks in damp and ferocious weather As an example
of the speed gained from using horses, over short
dis-tances (up to 5 kilometers) a horse can travel in the
range of 48 kilometers per hour A horse carrying
rider and saddle might make a trip of 480 kilometers
in sixty hours, and the time can be shortened by
fre-quent changes of mount A person in top condition—
for example, a soldier accustomed to long marches—
typically can walk around 65 kilometers a day
Horse-related technology also developed
continu-ously over time, adding to the effectiveness of horse
and rider, and horse and vehicle Bit and reins,
stir-rups (not adopted in Europe until the early Middle
Ages), horseshoes, saddle and carriage designs, and
modern veterinary medicine, all brought new
capaci-ties to the horse power on which humankind relied
Not only was the horse an essential energy
re-source, but its presence also repeatedly changed
his-tory and society The rise of cavalry as a mobile force
in warfare and the change to a horse-based economy
and culture by North American Plains Indians when
horses were reintroduced by Spanish invaders are
only two of the many transformations wrought by
horse power
Other Animals as Energy Sources
Humans have attempted to put many kinds of large
animals to work, but only a few other species have
proved useful Of these, the most important have
been those already adapted to extreme climates and
terrains
The camel is called the “ship of the desert” because
of its ability to travel for long distances between water
holes Some desert nomad tribes organize their way of
life around the use of camels Normally employed as
pack and riding animals, camels were also
occasion-ally used in war in the ancient world, partly to frighten
the enemy’s men and horses Llamas, members of the
camelid family native to South America, serve as pack
animals in the Andes mountain region
Reindeer, adapted to living in an Arctic
environ-ment, can find forage on the barren tundra and
sur-vive temperatures of −50° Celsius Laplanders who
live in far northern areas have used them in the roles
filled by cattle and horses in warmer climates,
includ-ing ridinclud-ing, pullinclud-ing carts, and carryinclud-ing loads as pack
animals
Elephants, native to the Indian subcontinent and
to Africa, have been trained in both regions to lift and carry extremely heavy objects, although their use as riding beasts has been largely confined to ceremonial occasions and entertainment
Animal Power Today From prehistory through the nineteenth century, much of the work of civilization depended upon ani-mal power With the coming of steam power and the internal combustion engine, animals gradually be-came less essential for transport and traction, at least
in the developed world Yet as late as the 1930’s, horses or mule teams, rather than tractors, were used
by many American farmers
In Asia and Africa, most of the farmland is still worked with draft animals For a small farmer of lim-ited means or in an isolated area, animal power has several advantages Unlike machines, animals do not need complex networks to supply their fuel or parts for repair They produce their own replacements, and their malfunctions sometimes heal themselves with-out special knowledge or tools on the owner’s part Their by-products can be recycled into agricultural use
For these reasons, and because they bring less dev-astation to land and air, some members of “back to the Earth” movements in the United States choose animal power Heavy horses are also used in selected logging operations to avoid the clear-cutting and other envi-ronmental damage that machines bring
Emily Alward
Further Reading
Ableman, Michael From the Good Earth: A Celebration of
Growing Food Around the World New York: H N.
Abrams, 1993
Chamberlin, J Edward Horse: How the Horse Has
Shaped Civilizations New York: BlueBridge, 2006.
Chenevix Trench, Charles A History of Horsemanship.
Garden City, N.Y.: Doubleday, 1970
Clutton-Brock, Juliet Domesticated Animals from Early
Times Austin: University of Texas Press, 1981.
_ Horse Power: A History of the Horse and the
Don-key in Human Societies Cambridge, Mass.: Harvard
University Press, 1992
_ A Natural History of Domesticated Mammals 2d
ed New York: Cambridge University Press, Natural History Museum, 1999
Greene, Ann Norton Horses at Work: Harnessing Power