Stephen Hawking believes humans must colonize additional planets or face mass extinction.
According to the famous astrophysicist, it will be "difficult enough" to avoid disaster on planet Earth in the next hundred years, "let alone" the next thousand or million.
"The human race shouldn't have all its eggs in one basket, or on one planet. [So], let's hope we can avoid dropping the basket until we have spread the load," Hawking told the Big Think website.
"[Yes], I see great dangers for the human race. There have been a number of times in the past when its survival has been a question of touch and go. The Cuban missile crisis in 1963 was one of these. The frequency of such occasions is likely to increase in the future."
Hawking explained that humans would require "great care and judgement" to successfully navigate future events.
"But I'm an optimist. If we can avoid disaster for the next two centuries, our species should be safe, as we spread into space. [And] if we are the only intelligent beings in the galaxy, we should make sure we survive and continue.
"[Still], we are entering an increasingly dangerous period of our history. Our population and our use of the finite resources of planet Earth, are growing exponentially, along with our technical ability to change the environment for good or ill."
However, Hawking warned that human genetic code would inevitably carry the "selfish and aggressive instincts" that helped ensure the survival of Homo sapiens in the past.
"Our only chance of long term survival, is not to remain inward looking on planet Earth, but to spread out into space. We have made remarkable progress in the last hundred years.
"But if we want to continue beyond the next hundred years, our future is in space. That is why I'm in favor of manned space flight."