Dogs today come in many different shapes and sizes.
But when did this variety start? New research shows it began a long time ago, even before modern breeding methods.
Scientists looked at the sizes and shapes of 643 dog skulls and their wolf ancestors from about 50,000 years ago. They found that dogs began to show distinct physical features at least 11,000 years ago, around the time the last Ice Age ended.
The findings go against the idea that this kind of diversity is mostly something new that happened because of how humans bred dogs in the last few hundred years. The research showed that significant variation in cranial size and shape among dogs appeared soon after the divergence from their wolf ancestors.
The dog is descended from an ancient wolf population that is separate from modern wolves. The dog was the first animal domesticated by people.
