The difference in intelligence between humans and chimpanzees is tiny,’ he said. ‘But in that difference lies the contrast between 7 billion inhabitants and a permanent place on the endangered species list.
Some physicists believe that we live in an infinite sea of cosmological domains, each governed by its own set of physical laws. The universe might contain hidden gateways to these domains. Perhaps future humans will duck into a more habitable, longer-lived universe, and then another, and another, ad infinitum. Our current notions of space and time could be preposterously limited.
Earth is the cradle of humanity, but one cannot stay in the cradle forever.
If life is a cosmic fluke, then we’ve already beaten the odds, and our future is undetermined — the galaxy is there for the taking. If we discover that life arises everywhere, we lose a prime suspect in our hunt for the great filter. The more advanced life we find, the worse the implications. If Curiosity spots a vertebrate fossil embedded in Martian rock, it would mean that a Cambrian explosion occurred twice in the same solar system. It would give us reason to suspect that nature is very good at knitting atoms into complex animal life, but very bad at nurturing star-hopping civilisations. It would make it less likely that humans have already slipped through the trap whose jaws keep our skies lifeless. It would be an omen.