How does the fossil record show us that species have changed over time?

By looking at fossils, we can take a look at the history of life. Fossils are the preserved traces of an organism (animals or plants, for example) from the past. When we look at them we are basically looking at the past and at the life forms that inhabited Earth long before us. It is by looking at fossils of different periods of the past that we can see how species have changed over time!...

By looking at fossils, we can take a look at the history of life. Fossils are the preserved traces of an organism (animals or plants, for example) from the past. When we look at them we are basically looking at the past and at the life forms that inhabited Earth long before us. It is by looking at fossils of different periods of the past that we can see how species have changed over time!

If you look at rocks of more than 1 billion years old, you will only find fossils of single-celled organisms, the simplest forms of life. If you look at rocks of 550 million years old, you'll find fossils of simple multicellular beings.  Here, we can already see some sort of change in the life forms. With rocks of 500 million years old, you get ancient fish, but without jawbones! And when you look at rocks of 400 million years old, you'll find fish with jaws! Not only that, but as you start looking at younger rocks, you'll find more and more fossils of animals that look very similar to the present ones.

So, by looking at the fossil record we can compare the older fossils with the younger fossils, or even with the life forms of the present day. This comparison enables us to see the changes that occurred during the course of time.