The record shows several changes in the line of horses over time. It is now only one genus, Equus. This was around from about 23 to 2 million years ago. More recent ones showed gains in size, such as those of Hip parion. This happened with a kind of Mesohippus found from 40 to 30 million years ago. They also show a move to a habit of eating grass with changes for running from animals that may eat them. Fossils that followed show the change over time of teeth shapes and how the leg and foot are built. This group of remains shows the change in the body that came from drying over time that changed the land from a forest to a large space with a lot of grass. These then gave rise to the first horse-like kinds of animals 55 to 42 million years ago in the genus Eohippus. The record goes back to a dog-like ancestor some 55 million years ago. These show parts of the body that are in between earlier and later forms. Many have what are called transition fossils. The record of horses in North America is quite rich. The fossil record is made up of all the fossils that have been found to tell a story of the past and show how living things have changed over millions of years.įossil records with a lot of detail have been found for groups of species that have changed over time, such as whales and some horses. They sort them all over the world to decide when the life forms lived in terms of each other. Scientists figure out the age of these remains. This is because they show the changes from evolution. This causes groups of living things to change because the parents pass on what helped them live to their children.įossils give strong signs that livings things from the past are not the same as those found today. Evolution is when living things change over time to help them live long enough to reproduce. Since the time of Darwin, what we know about this subject has become clearer and broader. A large part of Darwin's book, On the Origin of Species, found patterns in the world around us that make sense with evolution. We are able to prove evolution in many ways. When they look at every level of living systems, biologists see the mark of past and present changes.

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