First DNA Life: From chemical reations before 4 billion years ago to replicating molecules about 4 billion years ago to DNA based life then to LUCA, the only DNA based branch to survive. Meaning, DNA based life likely started before LUCA, and LUCA is the only branch to survive the test of time. From LUCA to humans, RNA and DNA are essentially the same as today. They serve as the tools for genetic information storage, transmission, and expression through prokaryotes to eukaryotes, underpinning the diversity and complexity of life on Earth.

We don’t know what LUCA looked like, so the elongated image here is to represent a variety of very early shapes. The last universal common ancestor (LUCA) is estimated to have lived approximately 3.5 to 3.8 billion years ago. It is the organism from which all current life on Earth descended from. Your greatest grandparents. Although no LUCA fossils have yet been found, geneticists can study LUCA by analyzing the genetic information of its descendants. LUCA’s genetic legacy pervades all life on our planet, and the study of LUCA serves as a reminder of our intimate connection to the living world around us. As Carl Sagan once said,

“We are all connected; to each other, biologically. To the Earth, chemically. To the rest of the universe, atomically.”