A hand stencil left on an Indonesian cave wall at least 67,800 years ago may reveal how and when ancient humans reached a lost continent known as Sahul that once linked Australia with southeast Asia.

The outline of a hand made with red pigment on the wall of a cave in Indonesia at least 67,800 years ago may be the world’s oldest rock art, according to a new study.

The hand stencils were made by spraying mouthfuls of ochre mixed with water over a hand pressed to the cave wall.