Which theory historically proposed that life began with simple organic compounds formed in the atmosphere and ocean before evolving?

• A. Primordial Soup Theory
• B. Community clay theory
• C. Hydrothermal vent theory
• D. Panspermia

Answer: (A)

The idea being tested is that life began from simple organic molecules that formed in Earth's early atmosphere and oceans and then evolved through gradual chemical complexity. This primordial soup concept, proposed by Oparin and later by Haldane, envisions energy sources like lightning and UV light driving reactions that convert basic atmospheric gases into small organic molecules. These molecules accumulate in the shallow primordial ocean, creating a “soup” from which more complex polymers and eventually self-replicating systems could emerge, leading to life.

This view is distinguished from other ideas that place the origin of life in different settings. The mineral-surface or clay theory emphasizes catalysts on clay minerals guiding polymer formation, not atmospheric/ocean chemistry. The hydrothermal vent theory points to life beginning at deep-sea vents where chemical gradients at high temperatures and mineral-rich fluids drive synthesis. Panspermia suggests life started somewhere else in the cosmos and was transported here. The primordial soup concept specifically ties the origin to early atmospheric and oceanic chemistry before evolving into more complex biological systems.