Why do giraffes have long necks?
For grown-ups: the science
Giraffes with necks that made high leaves easier to eat became more common over a long time.
Scientists think giraffes' long necks are a trait that evolved through natural selection over many generations. Reaching high leaves may have helped, and males swinging their necks to compete may also have played a part. A neck does not grow longer in one lifetime and then get passed on. Instead, giraffes with inherited neck-length differences had more babies over many generations, so long necks spread through the group.
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Transcript
A giraffe stretches up to eat leaves from a tall tree. Why is its neck so long?
Giraffes eat leaves high up in trees. Their long necks let their mouths reach leaves that are hard for other animals to reach.
Long ago, some giraffes had a little longer necks than others. Those with longer necks could eat leaves more easily and often grew up.
Grown-up giraffes had babies, and neck-length differences were passed along. Over a very long time, giraffes with long necks became more common.
Giraffes with necks that made high leaves easier to eat became more common over a long time.