For more than 3 billion years, organisms on Earth have relied on a standard set of 20 amino acids to build the proteins that carry out life’s essential actions. But did it have to be this way? There are more than 20 amino acids available in nature, and scientists have long wondered if life could have arisen based on a different set.

Researchers with the NASA Astrobiology Institute (NAI) have devised a test to try to learn if the 20 amino acids Earth’s life uses were randomly chosen, or if they were the only possible ones that could have done the job. The team used computers to estimate the fundamental properties of the 20 amino acids life uses, and the results indicated that life did not choose its 20 building blocks at random.