7.13 Origins of Life on Earth

Earth formed about 4.6 billion years ago; the earliest fossil evidence of life is around 3.5–3.9 billion years old.

Miller-Urey (1953) showed simple inorganic molecules + energy can form amino acids under early-Earth-like conditions. Hydrothermal vents are another proposed setting.

RNA can store information AND act as an enzyme (ribozymes), so it may have come before DNA and proteins. Lipids self-assemble into protocells (vesicles), creating compartments.

Sequence (hypothesis): inorganic molecules → organic monomers → polymers → protocells → self-replicating RNA → cells.

Worked example: Why is RNA, not DNA, thought to be the first genetic material? → RNA can both carry information and catalyze reactions.