If you’re of the opinion that Life has an inherent (and rather twisted) sense of humor, this may explain why-

Laughing gas and the mystery of Carl Sagan’s Faint Young Sun Paradox: When the sun shone dimmer an eon ago, Earth remained warm in spite of it likely thanks to a mix of greenhouse gases. Biogeochemists have now shown how N20, known today for its use as a dental anesthetic, may have made it into the mix.

Source: Laughing gas may have helped warm early Earth and given breath to life — ScienceDaily