Constructive neutral evolution

Imagine that you have a toy box and you love playing with all the toys in it. Every time you play with a toy, you might make it a bit different by adding stickers, painting it or even breaking a part of it. Sometimes these changes could make the toy better, but sometimes they could make it worse or just not change it at all.

Constructive neutral evolution is kind of like playing with toys in your toy box. The idea is that sometimes, even small changes to something in nature (like a living organism) might not make a difference to how well it can survive and reproduce – it's just neutral. However, over time, these small neutral changes might accumulate and create a new trait that's actually beneficial! This means that even though each change by itself wasn't helpful, when they're combined together, they can create something important.

For example, imagine that you have a stack of blocks, and each one is a slightly different size. It might not matter much if you pick up one block that is slightly bigger or smaller than another. But if you keep picking up bigger blocks and adding them to the stack, eventually you'll have a tower that's much taller! Each individual block didn't make a huge difference, but when you added them all up, you ended up with a big change.

In biology, constructive neutral evolution could happen if different versions of a gene (like different sizes of blocks) are maintained in a population, even if they don't make a difference to how well an organism functions. Then, over time, a combination of those neutral versions could create a new trait that ends up being really useful! This kind of evolution is different from something like natural selection, where traits have to be immediately beneficial in order to stick around. Instead, constructive neutral evolution allows for traits that are built up over many small changes.