Scientists have few clues to go on. Fossil records from this era are incomplete, and researchers are still debating whether the stuff of life zoomed to Earth on meteorites or bubbled up from deep-sea thermal vents. Wherever life came from, scientists believe it appeared on Earth around 3.8 billion years ago. They think the key ingredients were nonliving molecules like carbon dioxide and methane. Early attempts to re-create life by combining these ingredients in a chemistry beaker, however, failed miserably.
Life has a highly ordered structure.
It is more like a lasagna, in which ingredients are combined and layered in a particular order, than like soup, in which ingredients are simply tossed into a pot. Instead, scientists have to work backwards, like chefs who have tasted a delicious dish and are trying to re-create the recipe. Since they can't travel back in time, scientists are trying to create the first living molecule in chemistry labs and on computers. It must have been able to be reproduce. It must have had some sort of purpose, or carried some key bit of information in its structure.