Makes sense that if you have Hydrogen, Carbon, and a reducing agent under tremendous heat and pressure, you end up with simple hydrocarbons.
And we know how easy it is for simple HC chains to link up and become heavier.
But no doubt there are biochemical markers in SOME oils.
I think there are both processes going on, and it will never be an either/or proposition.
Lets take the theory of circulation that the human body applies and apply it to the earth. It makes for a pretty interesting analogy for exploration purposes.
If rivers lakes and streams are like the blood flow of the earth, where is its digestive system and where does its "waste product go? What "food" does the earth consume.
Somewhare in that anology awaits the discovery of how oil is made by the earths geologic processes. We make methane
( some of us doo, others make hydrogen sulfide, depending on the type of colonic bacteria we have?).
Anyway food for thought. Once we now the process , we might be able to find more oil, or even duplicate the process by speeding it up under artificial conditions.