Life emerged on Earth in an ultramafic world under anaerobic conditions and conditioned by particular environmental characteristics for which no record remains.
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![Odds ratio of the hypotheses that abiogenesis is a fast vs slow process. Each curve represents the odds ratio, computed using Equation 1, as a function of the biosphere’s ultimate lifespan, T - although we have subtracted off the modern epoch to yield remaining time on the x-axis. Previous estimates [1, 8] for the earliest evidence of life yield the dotted and dashed lines, but the new LUCA date of 4.2 Gya [10] greatly improves the odds factor. Indeed, the three solid lines show how the odds are always above 10:1 irrespective of how one chooses T or indeed fairly extreme choices (Carboniferious and Cambrian period) for the earliest civilization on Earth, t ′ I - evident by the circles which denote the minima. -- astro-ph.EP](https://i0.wp.com/astrobiology.com/wp-content/uploads/2025/04/Strong-Evidence-That-Abiogenesis.png?resize=1200%2C721&ssl=1)