Molecular weight distribution: Universality across life and potential for statistical biosignatures

As scientists try to detect life elsewhere in the universe, one of the biggest challenges is how to eliminate biases of “what we think life is” and reduce the likelihood of false positive biosignatures. Using big data of biology and investigating any universal characteristics shared across all-known life forms is a first step to understand how life is characterized in relation to non-life. In this work, around 20,000 different taxa in the three domains of life are analyzed to study any universalities or varieties across biology. Specifically, the focus is on investigating the complexity of chemical substances utilized by a large number of diverse organisms sampled from across the three domains of life. Molecular weight is used as a measure of chemical complexity since it is an obtainable variable in space missions and is a good proxy of the possible combination and configuration of atoms in molecules. The results show that regardless of the rich diversity of life across the three domains of life (archaea, bacteria, and eukarya), they share similar distribution patterns, which is not observed in non-biological data. These results are consistent with the idea life preferentially selects specific chemical space out of the vast possibilities unlike non-life. Further clarifying the universalities and varieties across diverse life forms can be useful as a theoretical basis for defining new biosignatures and predicting patterns indicative of life.