Today we know that whales are aquatic mammals, highly adapted to live in their ocean environments, but what did they evolve from?

 

It turns out this question has had a long history in science, going back to Charles Darwin. It’s only in the last 30 or so years that we’ve figured out what animals whales evolved from. Today we’ll trace the evidence of whale evolution to determine their ancestors.

 

As you work through the whale evolution story you will see:

1. How whales evolved and what animals they evolved from
2. How evolutionary theory makes specific predictions that can be tested by evolutionary biologists

 

Open your packet, but do not open any of the smaller packets inside. You should have:

• A picture of a Sperm Whale skeleton
• A timeline of the Eocene Epoch

 

Take a look at the skeleton of the modern sperm whale. Circled in red are some tiny bones. These bones derive from the animals hind limbs, or the rear legs of an ancestor. We call these traits ‘vestigial’; ‘vestigial’ traits have no function to an animal today, but probably helped their ancestors survive in the past. Even humans have vestigial traits, one example is the appendix. Over time vestigial traits have the tendency to become less and less developed.

 

Now that we know that whales have vestigial hind legs, what does this tell us about ancient whale ancestors, were they terrestrial (land-dwelling) or aquatic (water-dwelling)?