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Powerpoint Presentation: Evolution of the Horse

Evolution Index

The origins of life
Evolution and Fixity
Natural selection
Lamarkian Evolution
Antibiotic Resistance
Industrial melanism
Palaeontology : The study of fossils
The C-14 Decay Curve
In Search of Deep Time
Punctuated Equilibrium
The classification of living organisms : Taxonomy
Kingdoms
Humans: Neotonous, bipedal African apes
The Hominids
The Changing Trees of Human Evolution
Genetic verses Cultural Evolution
Phenylketonuria (PKU) Fact Sheet
Cystic Fibrocis (CF) Fact Sheet

Topic Chapters Index

References

Stephen J Gould (1991) Bully for Brontosaurus Penguin Books

The case of the creeping terrier clone.

The use and abuse of school text books.

Life's little joke

The changing views on the evolution of the horse.

Bully for Brontosaurus

The principle of precedence in scientific names.

Web sites:
Talks Origin Archive exploring the Creation/Evolution Controversy Horse Evolution
Katheleen Hunt Copyright 1995

Horse Evolution

EVOLUTION

Custom Search

Evolution of the Horse

Evolution of the Horse

this chart is also available in .pdf format

Horses belong to the Perissodactyla, the odd-toed ungulates. This group includes horses, rhinos and tapirs today but it was a much more diverse group 50 million years ago.

The genus Equus includes horses, zebra and asses, are themselves the last remaining branch of a diverse group of equids. This is similar to the status of Homo sapiens being the last remaining species of a once diverse group of Hominids.

The evolution of the horse, however, is much better documented than ours. The fossil record is very complete.

 

In the evolution of the horses we can see a number of trends:

  • Increased size

  • Reduced number of toes and longer legs

  • A stiffer back

  • Larger teeth and a larger skull to hold them

  • Teeth with bands of hard and soft material on the crown

  • Open tooth roots permitting continuous growth

 

The trends correspond to changes in the climate and vegetation of the Earth over the past 55 million years, combined with an arms race between predators and prey.

FROM rich rainforest which covered most of the Earth in which the horses ancestors browsed on leaves and hid from predators.

TO open savannah grassland where the modern horses grazed grass and had to run from predators.

The view of evolution in Darwin's day was that of Gradualism. One species slowly transforming into another.

 

The modern fossil record reveals a different picture.

  • Periods of radiation where species diversify and fill different niches.

  • Species giving rise to new species whilst they still thrive. Species do not "turn into" new species and completely disappear.

  • The result is a more bushy appearance of the pathway of evolution not a linear ladder.

  • An irregular rate of evolution.

 

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