The headline on that article says "of prion disease," but it's prions' origin they found. Some prions are useful in our body.
Amazingly enough, it appears that prions are related to a couple proteins called ZIP6 and ZIP10, which are metal ion transporters that help zinc into the cells.
I say "nailed down" in the 1st paragraph, but we know that something like this isn't going to be "nailed down" without a lot more evidence. Still, the indicators that the ZIP molecules and prion molecules diverged way back when the chordata phylum was formed, which would be hundreds of millions of years ago, are so strong that researchers said:
Schmitt-Ulms is confident that the many corroborating pieces of evidence collected and, equally important, the absence of any conflicting observations, allow no other conclusion to be drawn.
So what kind of evidence are we talking about?
- Prion and ZIP proteins contain extensive stretches of similar amino acid sequence.
- Respective segments within ZIP and prion proteins are computationally predicted to acquire a highly similar three-dimensional structure.
- Multiple additional commonalities between ZIP and prion proteins.
And what are those "multiple additional commonalities"? I wouldn't ask. The chances are you and I won't be able to understand most of the answer to that. But if you want to, I looked up the original article on the online journal PLoS ONE. Feel free to click that link.
You'll probably find the answer under "Quantitative interactome analyses" :-D.
DNA, its consistency in mutation, and all we know about its ability to code and thus change cells and life is really pretty astounding proof of all Darwin predicted in his theory of "the origin of species by natural selection" or "modification with descent." That Darwin could have seen all that without knowing about DNA or even about genes is impressive. Very impressive.