Universal paralogs provide a window into evolution before the last universal common ancestor

The study of early evolutionary history provides an account of how the foundational features of life as we know it first emerged. Phylogenetic analysis is a powerful method in the study of early evolution because it uses molecular evidence that has been inherited from the ancient organisms themselves. Here, we describe an important yet understudied type of protein family, universal paralogs, that retain phylogenetic signals from evolutionary events predating the last universal common ancestor of life, offering a unique window into early evolution. We survey recent advances in the study of universal paralogs and discuss how emerging computational tools enhance our ability to use these protein families to describe the very earliest stages of evolution with increasing detail and accuracy. Such research will greatly improve our understanding of how life emerged and subsequently evolved on the ancient Earth.