Scientists have documented five mass extinction events during Earth’s 4.6-billion-year history. Are we on the precipice of the sixth? Find out tonight on America’s Book of Secrets at 10/9 Central on The HISTORY Channel | Ancient Aliens

A large nation like the United States is bound to have many (dark) secrets, and those secrets are allegedly written in a special book. Catch new episodes of #AmericasBookofSecrets beginning Saturday 21 July, 7:05PM (SIN/HK) on H2! | HISTORY