With rising global temperatures, pollution, overfishing, ocean acidification, and other problems caused by humans, there’s no question that today’s coral reefs are in trouble.

As predictions about the future of these ecosystems grow increasingly dire, scientists are looking in an unlikely place for new ways to save corals: the past.

The reefs of yesteryear faced challenges too, from changing sea level to temperature shifts, and understanding how they survived and when they faltered can help guide our efforts to help ensure a future for reefs.