A pair of scientists looked at the rate at which the complexity of life increases and then extrapolated back to a point of zero complexity, aka the origin of life. The answer they came up with is 9.7 ± 2.5 billion years ago. Which is much older than the Earth. This idea has some provocative implications:
Sharov and Gordon say their interpretation also explains the Fermi paradox, which raises the question that if the universe is filled with intelligent life, why can’t we see evidence of it.
However, if life takes 10 billion years to evolve to the level of complexity associated with humans, then we may be among the first, if not the first, intelligent civilisation in our galaxy. And this is the reason why when we gaze into space, we do not yet see signs of other intelligent species.