Conversation so far:
How is Heyerdahl related to the expedition of Easter Island?
Heyerdahl organized the Norwegian Archaeological Expedition to Rapa Nui (Easter Island).
Who went with him?
The expedition's scientific staff included Arne Skjolsvold, Carlyle Smith, Edwin Ferdon, Gonzalo Figueroa and William Mulloy.

Question: When did they go?
Self-contained rewrite: When Thor Heyerdah and the expedition’s scientific staff go?