All life on Earth shares a common ancestor that lived roughly four billion years ago. This so-called “last universal common ancestor” (LUCA) represents the most ancient organism that researchers can study. Previous research on the last universal common ancestor has found that all the characteristics we see in organisms today, like having a cell membrane and a DNA genome, were already present by the time of this ancestor. So, if we want to understand how these foundational characteristics of life first emerged, then we need to be able to study evolutionary history prior to the last universal common ancestor.
In an article published in the journal Cell Genomics, scientists Aaron Goldman (Oberlin College), Greg Fournier (MIT), and Betül Kaçar (University of Wisconsin‑Madison) describe a method to do just that.
“While the last universal common ancestor is the most ancient organism we can study with evolutionary methods,” said Goldman, “some of the genes in its genome were much older.” The authors describe a type of gene family known as a “universal paralog,” which provides evidence of evolutionary events that occurred before the last universal common ancestor.