> does anyone ever suggest a prion LUCA[1] Yes, it totally makes sense to talk about a common ancestor! There's one known prion-disease-causing protein in hum

> does anyone ever suggest a prion LUCA[1] Yes, it totally makes sense to talk about a common ancestor! There's one known prion-disease-causing protein in humans, the "major prion protein". You can see the gene containing the code for this protein in human DNA, and any mammal DNA has a similar gene that is still very closely related. This suggests that the protein has some important function(s) in mammals, and has a common ancestor before these species existed. Genes that have a shared history but are less closely related (and don't appear to cause disease) can be found for example also in zebrafish ('Shadoo' gene) and in humans ('Doppel' gene). https://pubmed.ncbi.nlm.nih.gov/15449459/ https://pubmed.ncbi.nlm.nih.gov/15449459/