Last universal ancestor

So, a very, very long time ago, there was a tiny little thing, too tiny for you to even see, that was the very first living thing on Earth. It was so different from anything we have now, but it was alive!

This little living thing grew and grew and changed over a really, really, really long time. It grew and changed so much, that eventually it turned into all the living things we see around us today!

But, scientists wanted to find out where all those living things came from originally. They did lots of research and studied the DNA, or the tiny instructions in every living thing that tell it how to grow and be alive.

After a LOT of studying, they found out that all the living things on Earth share the same instructions in their DNA, that originally came from that first little living thing! It's like a huge family tree, and that very first living thing is the root that started it all.

They call that root the "last universal ancestor" because it was the last thing all living things can trace their family tree back to. It's really amazing to think about all the different plants and animals and people on Earth today, all starting from that one tiny little living thing!