August 05, 2017 at 06:04AM on Facebook

“As scientists speculate what kind of life might exist on other worlds, a provocative idea is taking hold: that alien life, unlike anything we know, might already exist here on Earth. The idea is that life might have arisen two or more times on our planet – not just once, as long assumed. Our form of life came to dominate, while other forms receded into the corners. This ‘shadow biosphere’ would be difficult to detect, since it might not contain DNA, proteins or the other molecules that we rely on to detect life.”
What the ctenophore says about the evolution of intelligence – Douglas Fox | Aeon Essays