The Last Universal Common Ancestor (LUCA) is the most recent organism from which all life on Earth descends. It is believed to have existed around 3.5 to 4 billion years ago. LUCA is not a single species but rather a population of organisms that shared genetic material, leading to the diversity of life we see today. LUCA is significant because it provides insight into the early evolution of life, including the development of basic cellular structures and metabolic processes. Studying LUCA helps scientists understand the relationships between different domains of life, such as bacteria, archaea, and eukaryotes.