The Hidden Clues in Whale Legs

Lexile: 970 | Grade: 7

Passage

Whales are known for being massive, smooth-bodied sea creatures, gliding through oceans with powerful tails and flippers. But did you know that whales once walked on land?

Scientists have discovered fossils that show whales had tiny back legs millions of years ago. These legs weren’t for swimming—they were for walking.

The theory is that whales evolved from land animals that slowly returned to the water over millions of years. As they adapted to aquatic life, their legs became smaller and eventually vanished on the outside. However, deep inside the whale’s body, tiny leg bones still exist today.

These leftover bones are called vestigial structures—parts of the body that no longer serve a clear purpose but tell a story about the past.

Studying vestigial structures helps scientists understand how animals change over time. In the case of whales, these hidden clues reveal a long journey from land to sea.

So next time you see a whale, remember—it carries history in its bones.