Large animals that migrate from the mainland to islands shrink over time. This evolutionary change, called "insular dwarfism," usually takes thousands of years. Now, scientists describe cattle on Amsterdam Island that shrank by 25% in merely 117 years.

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Large animals that migrate from the mainland to islands shrink over time. This evolutionary change, called "insular dwarfism," usually takes thousands of years. Now, scientists describe cattle on Amsterdam Island that shrank by 25% in merely 117 years.