An uncountable number. Billions and billions of simple multicellular organisms reproducing, until one (or some) of them develop this mechanism and use it to drastically increase their survival and chance at reproduction.

It makes me wonder at what stage of evolution it appeared. I'm thinking the simple wormlike animals of the early Cambrian era.

Probably none. Neurons are destroyed all the time.

I didn't know. Or maybe I just broke my dna wrong.

Looks like the 2015 research was with isolated neurons, whereas the 2024 research is with live mice and gives actual evidence that memory is affected.

Interesting. Maybe this is just a deeper dive into that?

The team pinpointed the cause of the inflammation: a protein called TLR9, which triggers an immune response to DNA fragments floating around the insides of cells.

No, neuron DNA isn’t passed to offspring.

We know a lot about connectivity” between neurons “and neural plasticity, but not nearly as much about what happens inside neurons”, she says.

I don't think it's necessarily describing that so much as what happens to the neurons during that process.

Granted, I only posted the article because I thought it was an interesting read and don't necessarily understand a lot of the finer points of it.