2 Artificial Selection

8/14/2019 2 Artificial Selection

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Artificial Selection

Domestication & BreedDevelopment


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To Succeed with Domestication

Adapt to environment

Provide nutrition needs

Meet social requirementsMust consider typical social organization of species

How to young learn to be adults

Problems

Vices, Aggression Impotence, Infanticide

Able to reproduce


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Domestication of the Horse

23,000 B.C.Southern France archeological site

Food cracked bones of as many as 100,000horses


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Start of Primitive Agriculture

4500-3500 B.C. Less nomadic Depletion of local herds Domestication

Means of dependable food supply Taming by-product of hunting Orphaned foal 2-12 months of age Adopt, raise and put to work

Ex. Turkestan Turkmenes Lived on mares milk and horse meat - Raised fillies/ate colts Tethered mares in season for wild stallions to breed Earliest selection criteria Milk Production


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Domestication of the Horse

Ass, Onager & Camel

domesticated before the

horse 3000 B.C. drawings of

Onager being ridden with a

nose ring and jaw strap

Horse domesticated in

numerous areas duringsimilar time period 3000-2300 B.C.


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Signs of Domestication

Caves of Sumeria (Perisian Gulf) 2800 B.C. First signs of selective breeding

Drawings of horse heads in 4 horizontal rows Different head profile types (convex, straight,

concave) and mane types (erect, hanging and

maneless)

Central Asia 2800 B.C. Drawings of horses hitched wearing snaffle-type bits


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Earliest Selective Breeding

TemperamentThose that refused to obey returned to wild or

used for meatMore agreeable animals remained in

comparative safety of captivity

Bred to other docile animals to produce good-

tempered foals


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Earliest Selection Criteria

Learning Ability - Trainability Horse transferred reliance to man

Food, protection and companionship Learned to overcome fears hunting lions, tigers, etc.

Xenophon 430 B.C. first recorded advocate of

training by reward.


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Other Traits

Speed and SurvivabilityWithhold water for several days

Release herd pointed in the direction of water

First to arrive were selected for breeding and

training


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Man Alters the Horse

Orthopedic Problems1000 B.C. Xenophon first asserted no foot,

no horse

500 B.C. Persians develop first horseshoes heavy cloth Other problemsOccurrence of genetic abnormalities

May select beauty over functionality Small, dainty hooves

Selection criteria for performance reducedversatility

Breeds


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Breed Development

Breed = group with distinctivecharacteristics that are transmitted to their

offspring. Initial development through natural

crosses and artificial selectionEnvironment important roleAdaptations of the 4 original types

Results in many breeding groups


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Breed Development

Distinctive Characteristics Extremes in Climate, Topography and Vegetation Conformation

Color Performance

Skills and Abilities well promoted by breed advocates

Intelligence

Disposition Suitable to Mans Purpose gaits


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Formal Development

Man bred early types to fix certaindesirable characteristicsLittle change if type was suitable

pony breeds are relatively pure almost directdescendants of one early type

Some breeds took centuries Outcrossing with numerous other breeds

Easiest to develop if trait can be fixed (set)

Get desirable and undesirable characteristics set One sire may have strong prepotence good and bad


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Genetic Evidence

DNA of ancient wild horses found in permafrost Sweden & Estonia 2000yr old remains, Alaska

28000 yr old remains Analyzed the mitochondria DNA

Mutations occur at a known rate = molecular clock

Maternal ancestry traced

Tested against 600 living horses From 25 breeds worldwide


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2 Artificial Selection

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