• Fossils provide evidence of species that lived in the past and have since gone extinct.
  • Consider the example of the horse, shown in the Figure below.
  • Fossil evidence, depicted by the skeletal fragments, demonstrates evolutionary milestones in this process.
  • Notice the transformation of the leg bones from having four distinct digits to that of today's horse.
  • The oldest horse fossils show what the earliest horses were like.
  • They were about the size of a fox, and they had four long toes.
  • Other evidence shows they lived in wooded marshlands, where they probably ate soft leaves.
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