The Birdman cult evolved from the use of the Hoa Hakananai’a statue.

Evidence

Rather than being abandoned along with the other monoliths, Hoa Hakananai’a was incorporated into the Birdman cult, was moved, placed in a hut and now entered a new phase of his life. — Neil MacGregor, A History of the World in 100 Objects, 1091

Categorization

• corroborated: 2 independent passages support this claim — Neil MacGregor, A History of the World in 100 Objects, 1091