In the island’s caves, ghosts whisper to us from the far past. Paintings of the Sulawesi warty pig are the oldest known figurative art in the world, dating back 51,200 years. Accessing some of these cave paintings requires special government permission: Visitors, taken up a 30-foot cliff by expert rope-climbers, are allowed to spend only a few minutes at a time in the caves, to minimize carbon-dioxide damage. Some artworks show half-human, half-animal figures, giving us the earliest examples of symbolic thought and suggesting that our ancestors viewed the two life-forms as deeply enmeshed.