William F. Martin says that the Last Universal Common Ancestor can be traced back to deep sea vents like this one off the Galápagos. Credit Universal History Archive/UIG, via Getty Images
A surprisingly specific genetic portrait of the ancestor of all living things has been generated by scientists who say that the likeness sheds considerable light on the mystery of how life first emerged on Earth.
This venerable ancestor was a single-cell, bacterium-like organism. But it has a grand name, or at least an acronym. It is known as Luca, the Last Universal Common Ancestor, and is estimated to have lived some four billion years ago, when Earth was a mere 560 million years old. Read more.