Mutations don't always grow weaker. Some mutations have a positive effect on the organism in which they occur. They are called beneficial mutations. They lead to new versions of proteins that help organisms adapt to changes in their environment. Beneficial mutations are essential for evolution to occur.

One example is MRSA, it's bacteria that mutated to be antibiotic resistant. For that bacteria, that is a positive mutation. It sucks for us, but it's great for the bacteria.

I won't bother with the rest of the tweet if the first few words are wrong.