At some point, chemistry on the young Earth crossed into biology. We know life exists and evolves, but no one has reconstructed the sequence that first turned nonliving chemistry into a self-sustaining, evolving system.
Researchers have identified plausible pieces of the puzzle: organic molecules can form naturally, chemical reactions can assemble components, and laboratory systems show that some molecules can copy or catalyse reactions. These are important demonstrations, not a complete account of the first living system or proof of one specific pathway.
Open questions include where the transition happened, which molecules came first, and how a membrane, metabolism, and reliable inheritance became linked. The ancient evidence is sparse, and the conditions of early Earth are reconstructed indirectly. Several routes—such as shallow ponds or hydrothermal settings—remain under investigation.