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.”