Read this: The Chamorros, Guam's indigenous people, settled the island approximately 4,000 years ago. Portuguese explorer Ferdinand Magellan was the first European to visit the island on March 6, 1521. Guam was colonized in 1668 with settlers, like Diego Luis de San Vitores, a Catholic missionary. Between the 1500s and the 1700s, Guam was an important stopover for the Spanish Manila Galleons. During the Spanish–American War, the United States captured Guam on June 21, 1898. Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898. Guam is amongst the seventeen Non-Self-Governing Territories of the United Nations.

When did Guam's indigenous people first arrive?
What is the answer? (If it cannot be answered, return "unanswerable")
4,000 years ago