Life—at least, as we know it—needs 20 amino acids, which it combines into the proteins that build living tissues. How life actually arrived at a minimum of 20 canonical amino acids (CAAs) in its journey from primordial ooze, however, is still a mystery. Some microbial species use up to 22 amino acids, but no species on Earth uses fewer than 20.

However, that may not have always been the case. Curious about how the precursors of life may have made it on a hostile young Earth before LUCA (the Last Universal Common Ancestor of all organisms) finally came into being, a team of researchers from Columbia University set out to see whether microbes emerging back then could have possibly run on fewer than 20 amino acids.