Why can't penguins fly?

Penguins have wings, but they are not like a bird's wings. Their wings are small, stiff, and flat, just like a paddle. Millions of years ago, penguins' ancestors could fly. But over time, catching fish in the sea became more important than flying.

To fly, an animal needs light bones and big wings. Penguins' bones are heavy and solid instead. This weight cannot hold them up in the air, but it helps them dive easily into the water. They use their wings like paddles and almost seem to fly through the water.

So it is as if penguins chose to fly in the sea instead of the sky. This helps them catch food like fish, krill, and squid very fast.