Evolution of the Horse: From the Swamps to the Sweeps By Dr. Jenifer Nadeau Dept. of Animal Science...
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Transcript of Evolution of the Horse: From the Swamps to the Sweeps By Dr. Jenifer Nadeau Dept. of Animal Science...
![Page 1: Evolution of the Horse: From the Swamps to the Sweeps By Dr. Jenifer Nadeau Dept. of Animal Science College of Agriculture and Natural Resources, UConn.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f535503460f94c78914/html5/thumbnails/1.jpg)
Evolution of the Horse: From the Swamps to the Sweeps
By Dr. Jenifer Nadeau
Dept. of Animal Science
College of Agriculture and Natural Resources, UConn
![Page 2: Evolution of the Horse: From the Swamps to the Sweeps By Dr. Jenifer Nadeau Dept. of Animal Science College of Agriculture and Natural Resources, UConn.](https://reader035.fdocuments.in/reader035/viewer/2022062320/56649f535503460f94c78914/html5/thumbnails/2.jpg)
Lecture Objectives
• Define evolution• Describe the horse family tree • Describe the horse’s anatomical changes
and why they came to be
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What is evolution?
A gradual process in which something changes into a different and usually more complex or better form
Change in the genetic composition of a population during successive generations
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3 Mechanisms of Evolution
• Genetic Drift• Mutation• Natural Selection
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Horses are a Classic Example of Evolution
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Scientific Classification of the Horse
• Kingdom• Phylum• Class• Order• Family• Genus• Species
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The earliest ancestors of the horse appeared over 50 million
years ago.
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Time Line
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Recent: 10,000 years ago to present
Pleistocene: 2.5-0.01 million years ago
Pliocene: 5.3-2.5 million years ago
Miocene: 24-5.3 million years ago
Oligocene: 38-24 million years ago
Eocene: 58-38 million years ago
http://hometown.aol.com/darwinpage/horses.htm
Horse Family Tree
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http://www.angelfire.com/mi/dinosaurs/horse.html
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Eohippus or Hyracotherium50 million years ago
• About size of a fox, 2 feet long, 8 inches tall at withers
• Long skull with 44 low crowned even teeth without cement
• Originated in
N. America
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Eohippus50 million years ago
• Carried its weight on central pad like a dog
• Well adapted to living in forested and swampy environment
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Miohippus or Mesohippus35 Million Years Ago
• “Middle horse”• Larger (2 x size of Eohippus)• 3 hoofed toes on the front and hind, side
toes on each leg touching the ground• Splint of 2nd digit
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Miohippus or Mesohippus
• Low crowned teeth without cement• Teeth suitable for grazing on the prairie• Greater speed, endurance for finding
forage, water, protection, survival
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Merychippus25 million years ago
• Gave way to at least 19 new grazing horse species – “Merychippine Radiation”
• The 3 major groups included: Hipparions, Protohippines, true Equines
• Gave rise to the first burst of diversity in the horse family
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Merychippus
• Over 2 feet tall (35 inches)• Long crowned teeth with cement• Eye socket position changes
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Merychippus25 Million Years Ago
• 3 hoofed toes on each leg with smaller side toes touching the ground
• Bones of the leg began fusing together
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Pliohippus10 Million Years Ago
• Body equipped for savanna type conditions
• Higher crowned molars develop for grinding grasses
• 1st single-hoof equine• No recognizable side
toes• 12 hands tall
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Pliohippus
• One toe on front and hind legs• Splints of 2nd and 4th digits• Long crowned teeth with cement• Grandfather of the modern horse
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Equus6 Million Years Ago
Develops into modern day horse after 15 million generations
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Equus’ Evolutionary Changes
• Increase in body size• Reduction in toe number• Increase in size of cheek teeth• Longer face
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Evolutionary Changes in Horse Body Size
http://www.txtwriter.com/Backgrounders/Evolution/EVpage03.html
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During the Ice Age, Equus migrated from
North America throughout the world over the Bering Strait
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Equus
• One toe on front and hind legs• Splints of 2nd and 4th digits• Long crowned teeth with cement• Found all over Asia, Africa, Europe, and
North America
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Extinction in Western Hemisphere
• The appearance of man in the Paleolithic period
• Return to the continent at the Age of Exploration
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Why? Where did they all go?• Glacial cold?• Insects?• Disease?• The acts of man?• Starvation?
• Other mammals that became extinct or disappeared from the W. Hemisphere in the Pleistocene epoch include rhinoceros, camels, saber-tooth tigers, elephants, and the mastodon
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Survival of Equus
Members of family Equidae that survived:• Equus hemionus• Equus burchelli• Equus grevyi• Equus asinus• Equus caballus
Escaped to Asia by land bridge
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Equus Caballus - The First 5• 5 distinct subspecies of Equus caballus
developed west of Siberia and China• Przewalski horse• Tarpan• Proto-Oriental• Proto-Warmblood• Proto-Draft
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Proto-Draft
Proto-Warmblood
Proto-Oriental
Przewalski Horse
Tarpan
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Lecture Objectives
• Define evolution• Describe the horse family tree • Describe the horse’s anatomical changes
and why they came to be