Common descent

Hello! So you want to know about common descent, right? This is a big idea in biology that says that all living things on Earth are related to each other like a big family tree. Here's how it works:

Imagine you have a big family with lots of cousins. You know that you and your cousins all have the same grandparents, and your grandparents had their own parents before them, and so on. This means that you and your cousins all have the same ancestors - your great-great-great grandparents and even further back.

Well, in the same way, all living things on Earth are part of a big family tree that goes back billions of years. This means that humans, animals, plants, and even bacteria all have the same ancestors, way way back in time.

Scientists can tell which living things are related by looking at their DNA. DNA is like a code that tells each living thing how to grow and work, and it contains important information about how different organisms are related to each other.

So, scientists know that humans are related to apes, because we share a lot of the same DNA. And apes are related to monkeys, and monkeys are related to lemurs, and so on.

And this doesn't just apply to animals, it applies to plants and other organisms too. All life on Earth is connected and related through a common ancestry.

So, in summary: common descent is the idea that all living things on Earth are related like a big family tree, and share the same ancestors way back in time. Scientists can tell how different organisms are related by looking at their DNA.