I thought that evidence was pointing to us being the product of about 9.5 billion years of evolution. Given that we live on a 4.5 billion year old world, life would have had to survive some sort of space-gap before getting to earth.
If sentient life takes 9.5 billion years to evolve, and the universe is only 13.5 billion years old, life would have had to start evolving relatively fast for it to get this far. The earlier you go in the universe's history, the more rare planets become. Even more rare would be a planet orbiting a star hot enough to fuel life, but also in continuous operation for that long. If it really does take 9.5 billion years for life to reach this level of complexity, and in our case it survived the destruction of a planet to spread to a new one, then the Fermi paradox all-but disappears and likelihood that sentient life is currently extremely rare, or even unique to our planet increases dramatically.