I agree that "evolution" is usually a rather vague concept. In biology, however, we do have Darwin's definition based on the "strong principle of inheritance",

I agree that "evolution" is usually a rather vague concept. In biology, however, we do have Darwin's definition based on the "strong principle of inheritance", involving differences in fitness among hereditary variations. Both methylation and cultural change fail the "hereditary" criterion in this strict definition. It might be possible to analyze cultural change, to some extent, on these lines, provided the units of selection are well picked. (Dawkins made a brave attempt with "memes", but the only credible uses of that theory that I've seen involved peripheral phenomena, like earworms and various other inconsequential fads.) Methylation doesn't seem to fit that bill.