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Bit by Bit: The Darwinian Basis of Life

Figure 2

Potential pathways to life on Earth, beginning with a habitable planet and ending with DNA/protein-based life.

The planet is an artist's conception of the recently discovered [12] “Earth-like” planet Kepler-22b (image courtesy of NASA/Ames/JPL-Caltech). Prebiotic chemistry is represented by the Miller-Urey spark-discharge apparatus (modification of photo by Ned Shaw, Indiana University). Two examples of hypothesized pre-RNA life are shown, based on either threose nucleic acid (TNA) or glycol nucleic acid (GNA).

Figure 2