Evolution and domestication of the horse. 말의 가축화

A1. Evolution and domestication of the horse, micro-evolutionary consequences, related species, inter-species hybrids

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Evolution

- Evolution is well documented. Horse evolution covers a period of 60 million years

- Most important evolutionary forms of horse: Eohippus / Mesohippus / Mio-, mery-, pliohippus / Equus

- Most important changes in evolution of horses

1. in size, toe reduction, diet (omnivores -> herbivores=plant eating), teeth, skull

2. Changes on forefoot bones- lengthening of radius, canon bone and terminal phalanx From 4 metacarpal bones -> 3​

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Domestication

Occurred ~5,000-6,000 BC

1st – Central Asia, later in Persia, Egypt & Europe (3,000-4,000 BC) (origined from north America)

​Based on mitochondrial examination, Tarpan (equus ferus ferus) /Tarpan subspecies is main ancestor.

​Wild horses: Przewalkski horse is only remaining wild spp

Feral horses: Have domestic ancestors but were born & live in wild

(‘dedomesticated’) -> Mustangs, Bramby ​

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Consequences of microevolution domestication:

[Microevolution is the change in allele frequencies that occurs over time within a population, due to many processes.]

​1. Fusion of chromosomes

o Wild horses – 66/64

o Asses (donkey) – 62 , remained the same

o Domestic horses – 66/64

o Only assumed (has not yet been proved. Chromosome no. of Tarpan is unknown)

2. New Mutations & selection

O more then 200+ breeds, increase in breed groups & types, (increase diversity)

3. Size variation

o Height at withers (50-180cm)  Horses & ponies (withers is the tallest spinous process of the thoracic vertebras)

o Dwarfism – Falabella, Shetland pony (a breed of pony from the Shetland islands)

4. Change in build & conformation

o Draft horses, light horses etc.

o Breed characteristics (Roman nosed= a muzzle with convex profile, dished face)

5. Weight variation

Between 50-1200 kg

6. Diet – Less effective feed conversion

Accelerated ageing

• Reduced immune system & increased sensitivity to certain diseases (e.g. decreased resistance to respiratory diseases)

Colour variations

7. Sexual activity consequences of micro-evolution of the horse:

o Poorly expressed sexual dimorphism (the existence of two different forms (as of color or size) of a species especially in the same population // sexual dimorphism)

o Reduced fertility in some breeds

o Monoestrus (only one breeding season per year)-> seasonally polyoestrus ​

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Basic Terminology- to describe horses of various sexes, age and life cycle

Foal: Horse of either sex <1year old

Yearling: Horse of either sex between 1 & 2 years old

Filly: Female horse <4 years old

Mare: Female horse >4 years old

Colt: Male horse <4years old

Stallion: Entire (non-castrated) male horse >4 years old

Gelding: Castrated male of any age

Rig: Stallion with an undescended testicle

Female ass: jennet

Male ass: jack​

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Related species:

Taxonomy (groups):

Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Perissodactyla (non-ruminant, hooved animals)

Family Equidae

Genus Equus

Species

• Wild horses – Equus ferus Boddaert

• Prewalski horse/Taki – Equus ferus Prewalski

• Tarpan – Equus ferus ferus

• Domestic horse – Equus caballus

feral horse: “wild” (free roaming) – mustang, brumby (Australian), sorraia/ garrano (Portugal)

Subgenus Asinus (African ass/donkey)

Species

• Equus asinus/africanus ​

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Interspecies hybridization

Mule – Male ass-donkey (jack) & mare (=female horse). Usually sterile

Hinny/jennet – Female ass-donkey (jenny) & stallion (=male horse). Less common. Also infertile.

Zebra mules (zorse, zonkey)

Wild horse + domestic horse= successful, fertile offspring

Horse (domestic/wild) + ass (donkey) = successful, not fertile, except rarely in mares.

Horse + zebra = not fertile (zorse)

Asses + zebra = not fertile

Haldane’s rule: primarily the heterogametic sex (male) is affected by sterility in crossing of closely species

Heterosis: inter- specific hybrids may show higher strength, endurance, tolerance and resistance to heat/ diseases (mules)

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다음 : [동물육종학] 2. Main reproductino features of the horse

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