Where does oil come from?

With apologies to Soundgarden, our cars aren’t burning dinosaur bones.

Instead, most scientists think oil started out as plankton and other tiny ocean critters, specifically their lipids—tough, stringy molecules that bacteria want to eat about as much as you enjoy dining on gristle or tendons. The idea is that, unlike the rest of the biologic material, lipids don’t get gobbled up by bacteria, instead falling out to the bottom of the ocean, where they’re covered by millions of years of sediment and eventually become oil.