[Sir Napsalot]

To prove my previous point, excerpt from the article:

'Unlike dogs and humans, cats have not evolved the complex facial muscles that allow them to make obvious expressions,' she said.

Cats don't need 'obvious facial expression' to communicate their thoughts. Obviously! You will know when they mean business just by looking at their eyes.

[Daffynition]

A few days ago the Daily Mail had a story about dog expressions and advised owners to watch their eyebrows.