Do you know who your ancestors are? No matter who you are, you can claim LUCA as a long-lost relative. LUCA stands for "last universal common ancestor," and was likely the single-celled being from which all life on Earth originated. It's likely LUCA lived around 4 billion years ago, and it is thought to have spawned two groups of uni-celled life: bacteria and archaea. Scientists also believed that 355 protein families descended from LUCA.

The idea that LUCA was only half alive stems from a theory that LUCA was not capable of a function that is common to almost all living cells: sending ions across a membrane to create an electrochemical gradient. The being then uses that gradient to make an energy-molecule. Studies suggest LUCA couldn't generate the gradient, but could create the energy-rich molecule by using an existing gradient. This theory suggests the idea that the first life on Earth used the natural gradient between vent water and seawater for its energy.