Every living thing on Earth shares a common ancestor from 3.5 billion years ago

All life on Earth — from bacteria to blue whales to oak trees to humans — descended from a single common ancestor, known as LUCA (Last Universal Common Ancestor). LUCA lived approximately 3.5–4 billion years ago, likely near hydrothermal vents on the ocean floor. The evidence for universal common ancestry includes the fact that all life uses the same genetic code (DNA/RNA with the same four bases), the same ATP energy currency, and nearly identical ribosome structures across all domains of life.