Duplicated genes that appear in every branch of the tree of life can provide us with insight into the evolution that occurred between the first lifeform and the last from which we all descend, geneticists claim.

As far as we can tell, life only evolved on Earth once, and everything alive today is a descendant of that initial breakthrough. However, the divergence that gave us mushrooms, mice, and maple trees probably didn’t take place straight away. That is, the tree of life had a trunk, possibly quite a long one, before it started branching off into familiar kingdoms like animals, plants, fungi, and bacteria, let alone into further divisions within each. 

The point immediately before the branching began is known as the Last Universal Common Ancestor (LUCA). We think we have learned something of LUCA’s nature by looking for traits all surviving lifeforms share. But what about LUCA’s predecessors? What can we learn about the steps that turned those first strands of RNA into LUCA? It’s widely assumed the answer is nothing, but a new paper challenges that view.

“While the last universal common ancestor is the most ancient organism we can study with evolutionary methods,” said Professor Aaron Goldman of Oberlin College in a statement, “some of the genes in its genome were much older.”

Attempts to reconstruct LUCA have reached the conclusion it was a relatively complex organism, one that could not have spontaneously appeared. Instead, LUCA was the product of a long period of evolution from simpler life.

Remarkably, Goldman and colleagues say they can expose some of that process by reconstructing LUCA’s genes.