Doesn't it amaze you to realize that we can trace life back billions and billions of years ago to single-celled organisms floating around in the ocean?

Scientists have discovered lava rock taken from the ocean floor that contains remnants of life that are billions of years old. Three point five billion years, to be precise.

At certain spots the ocean floor oozes lava, which cools and forms rock formations. Microorganisms set up shop on the surface of these rocks and thrive on their rich chemical content. The microbes leave traces of their presence in the rocks in the form of tiny tubes.

When researchers looked at three billion plus year old rocks and saw these kinds of tubes, they suspected that microbes once inhabited them. The most convincing piece of evidence was a type of carbon found in the tubes that's produced by living things. So far, this is one of the oldest traces of life ever found.