I read this, but I think the researcher overstates the case. The prions adapted, they didn't evolve. They are the exact same proteins, just folded somewhat differently. The missing element is variation/mutation.

These prions found an optimal way of folding based on their surrounding environment, but no new variations of the prions were created. To say that these prions evolved would be to say that ice crystals evolve when they find optimal ways of forming snowflakes in various atmospheric conditions. Sometimes you get big fluffy puff balls. Sometimes you get tiny icy pellets, sometimes you get sharp hexagonal flakes. It all depends on the atmospheric conditions and the crystallization properties of water, but you're not ever going to get regular pentagonal snowflakes or octagonal ones, and you're not going to get any snowflakes that can withstand greater than 0 degrees celsius. You won't find snowflakes adapting to the weather in the Bahamas, for instance.

Prions are strangely folded proteins that interact with *existing* proteins and cause them to also fold into strange shapes. Some strange folds are more likely to cause other proteins to take on the same strange folding. However, you will never get a *new* protein suddenly appearing. The folding is more akin to snowflake crystallization -- where ice crystals interact with existing water molecules to create a particular shape of snowflake -- than it is to actual DNA evolution, where the actual information encoded in the DNA can mutate and those mutations can subsequently be inherited. You'll never find a prion evolving into a different protein.

It's also similar to epi-genetics, where gene (de)activation sites are passed from one cell to its daughter cells. The actual DNA code has not changed, so the 'evolution' is not permanent, it's just a phenotypic adaptation, not true evolution. Reset the cell's markers and you get the original genome back.