The Fermi Paradox III

Peter then focused his thought about another possibility which is the Great Filter could be the jump from simple prokaryote cell to the complex eukaryote cell.

After prokaryote came into being they remained that way for almost two billion years before making the evolutionary jump to being complex and having a nucleus. 

If this is the Great Filter it would mean the universe is teeming with simple prokaryote cells and almost nothing beyond that

And there is also the possibility that even the most recent leap humanity has made from the medieval life to the Industrial Revolution is a Great Filter candidate.

While the leap from semi intelligent life to intelligent life doesn't at first seem like miraculous step, some scientist rejects the idea of an inevitable climb upward of evolution.