Final answer:
Charles Darwin was hired as the naturalist on the British ship, the Beagle, in 1831. His job was to observe and collect specimens during the expedition, and his observations and evidence became key to his theory of evolution.
Step-by-step explanation:
The person who was hired as the naturalist on the British ship, the Beagle, in 1831 was Charles Darwin. As a naturalist, Darwin's job was to observe and collect specimens of plants, animals, rocks, and fossils during the expedition. He spent more than 3 years exploring nature on the Beagle and his observations and evidence collected during the voyage became crucial in developing his theory of evolution.