The stability of the RNA bases: Implications for the origin of life

High-temperature origin-of-life theories require that the components of the first genetic material are stable. We therefore have measured the half-lives for the decomposition of the nucleobases. They have been found to be short on the geologic time scale. At 100 degrees C, the growth temperatures of the hyperthermophiles, the half-lives are too short to allow for the adequate accumulation of these compounds (t(1/2) for A and G approximate to 1 yr; U = 12 yr; C = 19 days). Therefore, unless the origin of life took place extremely rapidly (<100 yr), we conclude that a high-temperature origin of life may be possible, but it cannot involve adenine, uracil, guanine, or cytosine, The rates of hydrolysis at 100 degrees C also suggest that an ocean-boiling asteroid impact would reset the prebiotic clock, requiring prebiotic synthetic processes to begin again, At 0 degrees C, A, U, G, and T appear to be sufficiently stable (t(1/2) greater than or equal to 10(6) yr) to be involved in a low-temperature origin of life. However, the lack of stability of cytosine at 0 degrees C (t(1/2) = 17,000 yr) raises the possibility that the GC base pair may not have been used in the first genetic material unless life arose quickly (<10(6) yr) after a sterilization event. A two-letter code or an alternative base pair may have been used instead.