 The concept of a last universal common ancestor of all cells (LUCA, or the progenote) is central to the study of early evolution and life's origin, yet information about how and where LUCA lived is lacking. Today, the cells that make up all life on Earth are clustered into three broad groups: bacteria, archaea, and eukaryotes. A distant union between these two formed eukaryotes—cells with a nucleus that make up all the complex multicellular organisms including plants and animals. Among 286,514 protein clusters, we identified 355 protein families (∼0.1%) that trace to LUCA by phylogenetic criteria. 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. Their functions, properties and prosthetic groups depict LUCA as anaerobic, CO 2 -fixing, H 2 -dependent with a Wood–Ljungdahl pathway, N 2 -fixing and thermophilic.
– The first name on your family tree—in fact, on the family tree of every living creature—should technically be LUCA. As the New York Times explains, the acronym stands for the Last Universal Common Ancestor, an organism that lived about 4 billion years ago and became the ancestor of all life forms. Now, a new study in Nature Microbiology provides what its authors say is evidence that settles the debate about where this first life began: near hydrothermal vents, like those found near deep-sea volcanoes. Researchers at Germany's Heinrich Heine University say their genetic sleuthing has revealed that LUCA was tailor-made to live in such an environment—it was essentially "a heat-loving microbe that fed on hydrogen gas and lived in a world devoid of oxygen," in the words of Science. To figure out this genetic profile, the scientists examined 6 million genes associated with two simple and ancient forms of life, bacteria and archaea. After identifying genes that were shared between the two groups, they whittled the figure down to 355 gene families that met their criteria for having originated in LUCA, their joint ancestor. “It was flabbergasting to us that we found as many as we did,” says lead researcher William Martin. This smaller group of genes allowed them to create a snapshot of sorts of LUCA, one hailed as "remarkable" by a UCLA evolutionary biologist. But don't expect the debate to end. The study “is all very interesting, but it has nothing to do with the actual origin of life,” Cambridge chemist John Sutherland tells the Times. (In less ancient but still ancient news, the remains of more real-life hobbits have been found.)