The Unclear Origins of Oil

Excerpted from a post titled "The Unclear Origins of Oil" on Kevin Kelly's CT2 (Conceptual Trends and Current Topics) blog:

Crude oil is almost $140 per barrel. By now you'd think we would know where it comes from. The conventional wisdom is that oil descends from algae from eons ago. Lots and lots of algae. Unimaginable mounds of dead algae in quantities no longer found on this planet, pressed, and cooked into hydrocarbon liquids. Thus: fossil fuel. Others, notably the Russians, have an alternative theory that oil comes from non-biological carbon compounds deep in this planet, like the methane oceans we find on other planets. An emerging third theory is that bacteria living within rocks produce oil.