Core Proposition

Life arose from simple inorganic molecules through progressive chemical reactions in a primordial reducing atmosphere.

Key Points

Oparin (1924, Russian): Life originated in the ancient oceans ("primordial soup"). Simple molecules → organic molecules → coacervates (droplet-like aggregates) → protocells.

Haldane (1929, British): Similar hypothesis — early ocean was a "hot dilute soup" of organic molecules. Proposed UV radiation as energy source alongside lightning.

What they agreed on:

• Primitive atmosphere was reducing (no O2)
• Inorganic molecules → organic molecules via available energy
• Life did not arise by spontaneous generation of fully formed organisms
• Progressive chemical complexity preceded biological complexity

What was NOT known in their time: The structure of DNA (discovered 1953, same year as Miller-Urey), the genetic code, or the role of RNA in protein synthesis.

Modern Extension

RNA World Hypothesis: RNA (not DNA or protein) may have been the first self-replicating molecule, because RNA can both carry information (like DNA) and catalyse reactions (like enzymes). This bridges the "which came first, DNA or protein?" problem.

Cue Summary

Oparin + Haldane = life from chemistry in a reducing soup. No O2. Miller-Urey = experimental test. RNA World = modern extension.