Meet LUCA: The Tiniest Ancestor of Every Living Thing on Earth

Scientists have discovered that you, me, your dog, your plants, and even bacteria all came from ONE teeny tiny living thing billions of years ago called LUCA (which stands for Last Universal Common Ancestor). By studying the genes [the instruction manuals inside our cells] of creatures alive today, scientists are figuring out what this super-ancient ancestor looked like and how it lived. Imagine — everything alive today is related, like we're all in one giant family tree!