| UPDATED: 18:37, Thu, Jan 14, 2021 Link copied Sign up for FREE for the biggest new releases, reviews and tech hacks SUBSCRIBE Invalid email When you subscribe we will use the information you provide to send you these newsletters. Sometimes they'll include recommendations for other related newsletters or services we offer. Our Privacy Notice explains more about how we use your data, and your rights. You can unsubscribe at any time. The debate whether intelligent life - separate to humans - exists has raged for years. People draw on multiple sources and logic to conclude that somewhere at some point a developed civilisation must have been present. They point to historically significant and often unexplained phenomena: Ancient cave art that depicts otherworldly beings; tales of foreign lifeforms falling from the sky.