Life is an molecular engine propelled by (made for) evolution

"To Nowak, evolution is a well defined process that can be described as precise mathematical equations. Nowak believes that "the same principals governing complex life forms must have been present at the earliest, simplest molecular levels otherwise the origin of life would depend on an unlikely collection of disparate random events."
-I agree.

To Nowak Early Earth's "prelife was not a primordial soup of chemicals, but an active generative phenomenon in which mutation and selection were already acting on molecules. Only when some of them began reproducing, out competing the others, did life begin."
- and a feedback system, with mainly positive disturbances and cross transfers.
--> it's a natural phenomenon 

Source: link

Unpublished: Drake formula (2013: there is a 75% chance to find ET 1.400-4.000 light years away or 0-15.785 advanced technological societies could exist in the Milky Way)