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Fossils

Would this be evidence of evolution?

Fossils, like this dinosaur fossil, provide evidence of species that lived in the past and have since gone extinct. In other words, these fossils are evidence of evolution.

Fossil Evidence

In his book On the Origin of Species , Darwin included evidence to show that evolution had taken place. He also made logical arguments to support his theory that evolution occurs by natural selection. Since Darwin’s time, much more evidence has been gathered. The evidence includes a huge number of fossils. It also includes more detailed knowledge of living things, right down to their DNA.

Fossils are a window into the past. They provide clear evidence that evolution has occurred. Scientists who find and study fossils are called paleontologists . How do they use fossils to understand the past? Consider the example of the horse, shown in the Figure below . The fossil record shows how the horse evolved.

Evolution of the horse. Fossil evidence, depicted by the skeletal fragments, demonstrates evolutionary milestones in this process. Notice the 57 million year evolution of the horse leg bones and teeth. Especially obvious is 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. Through time, the climate became drier, and grasslands slowly replaced the marshes. Later fossils show that horses changed as well.

  • They became taller, which would help them see predators while they fed in tall grasses.
  • They evolved a single large toe that eventually became a hoof. This would help them run swiftly and escape predators.
  • Their molars (back teeth) became longer and covered with cement. This would allow them to grind tough grasses and grass seeds without wearing out their teeth.

Similar fossil evidence demonstrates the evolution of the whale, moving from the land into the sea. An animation of this process can be viewed at http://collections.tepapa.govt.nz/exhibitions/whales/Segment.aspx?irn=161 .

"Does The Fossil Record Support Evolution?" This video can be seen at http://www.youtube.com/watch?v=QWVoXZPOCGk (9:20).

Don't Call That A Duckbill!!

Student Exploration

Yum, Conifers

Because most of them went extinct and the Age of Dinosaurs ended and the Age of Mammals began, some people still think of dinosaurs as failed organisms. Somehow they weren't as good as mammals, they were flawed and these flaws did them in. Science no longer sees dinosaurs this way. Remember, science is an ongoing process where theories and views are reevaluated as new information comes in. The ongoing work of scientists has led to the recognition of Dinosauria as a distinct phylum all its own, as well as recognizing that not all dinosaurs went extinct, just the non-avian ones, which is a fancy way of saying dinosaurs are still around, we just call them birds. One reason for these advances are new fossil finds. As more and more finds were discovered and science advanced in other areas like geology, ecology, paleoclimatology, evolution and genetics, it became increasingly clear that dinosaurs were not just big lizards but something quite different and quite well adjusted to the world they lived in. Watch this video to find out about a truly remarkable find, a dinosaur with it's last meal preserved!

Extension Investigation

Use the resources below to answer the following questions:

  1. Why does Dr. Bakker hate the name duckbill? Explain your answer as fully as you can.
  2. How do the bills of duckbill dinosaurs differ from those of ducks?
  3. Why do large herbivores need to have large guts? What do they have in these guts that humans don't need?
  4. What was one suspicion of scientists that Leonardo confirmed?
  5. How do the teeth of duckbill dinosaurs differ from those of cows or horses? How did the vegetation that duckbill dinosaurs ate differ from the vegetation eaten by cows and horses today?

Resources

Summary

  • Fossils provide a window into the past. They are evidence for evolution.
  • Scientists who find and study fossils are called paleontologists.

Practice I

Use this resource to answer the questions that follow.

  1. Describe the evidence for evolution provided by fossils.

Practice II

Review

1. How do paleontologists learn about evolution?

2. Describe what fossils reveal about the evolution of the horse.

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