UKS2 Topic: Dinosaurs and Fossils Block J: Charles Darwin and his theory of evolution Session 2
Background about Darwin and fossils
Geology
Darwin was very interested in how rocks were formed and how they moved around after they were formed. This study is called geology.
Many rocks were formed when mud was compressed and made hard. Sometimes animal bones, shells and other body parts were also preserved in these rocks and these are what we call fossils.
Darwin read a book by Charles Lyell, a very famous geologist, who argued that most rock movements weren't because of volcanoes and earthquakes, but were actually because of rivers, waves, and wind erosion. Changes could be very small but over a very long time they would add up to make really big changes, like mountains growing.
Fossils
When Darwin went on his voyage round the world on the HMS Beagle, he managed to collect lots of fossils of previously unknown animals. He sent them back to England to be looked at by experts. They looked very like some of the living animals he had come across, but were often much larger.
Especially in South America, he found fossils of extinct giant animals like Mastodons (a bit like an elephant), the Mylodon (a giant sloth), the Glyptodon (a giant armadillo), and the Toxodon (a giant guinea pig). He also found fossils of horse bones when it was thought that horses had never lived in the Americas.
Darwin kept records of the types of rock the fossils were found in, which helped him work out what kind of environment they lived in.
When he got back to England he worked with a fossil expert called Richard Owen who helped him work out what the animals were and find out that they were like the animals found in South America at the time. This helped Darwin work out his theory of evolution.
Barnacles
Barnacles are sea creatures that create a hard shell and stick onto boats and rocks. Darwin studied fossils of extinct barnacles as well as living species for eight years and published four books about them.
By studying both the fossil and the living species of barnacles, Darwin showed how he could make a better theory of how they were all related to each other.
Problems of missing fossils
Darwin wrote in his important book, On the Origin of Species, about why there seemed to be no fossils of missing links between an older and a more modern species.
He explained that few animals became fossilised, and so few had come to the surface of the earth and found after being fossilised.
He did say that more fossils would be found that linked species. In 1860, the year On the Origin of Species was published, a fossil of a dinosaur with feathers, Archaeopteryx, was found in Germany. It was a clear link between dinosaurs and birds.
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