"What's our current scientifically-based understanding?"
I have no question that epigenetics is critical to even pretty simple life forms.  It is part of what regulates gene expression.  That includes turning off some genes permanently in various tissues as you do not want those genes to ever function in that tissue.  For example the genes that produce the pigment melanin  are turned off in most tissues other than skin and brain in mammals, fish, birds and reptiles.  After all, it is a total waste of metabolic energy to makes lots of melanin in bones.  Yet there is a mutation in chickens that does exactly that.  The mutation blocks the epigenetics from shutting down melanin production in that chicken's bones.  Our understanding of how a living organism knows which genes to turn off in which tissues is for all practical purposes non existent.  We know weird stuff impacts what gets epigenetic marks and how many such marks.  Identical twin studies often show dramatic differences between the epigenetics of the two twins.  We know sending someone into space for a while causes all kinds of epigenetic marks to be added.  Yet there is very little evidence that those differences result in anything phenotypical that can be measured.  So, are they really important at all?  Or simply random accidents of no consequence?  Give us 50 years and maybe we will have some hints.

All is well and good when you talk about specific tissues in a specific animal.  Now suppose there is some environmental stress that induces such changes in some tissue and that change allows that organism to out reproduce others.  Suppose the change is something going on in the fat body that makes the critter more resistant to the deformed wing virus.  Gee, such a change could be a huge advantage.  You are still faced with a big problem.  You changed the epigenetics in the fat body tissue but how do you get such a change into an egg or sperm?  This is really, really hard.  A queen or drone at emergence already has all its sex cells and does not make brand new clones of sex cells.  Yet, you need to stuff some changes into its DNA or perhaps its histones.  Maybe you want some gene to over express and need to acetylate a very specific tiny region in the histone protein.  Is there any way to get information from the fat body to that histone?  Well, maybe there is.  No living person knows the answer to that question today and likely will not know it for quite a few years.  In general an adaptation means doing more of some biochemical metabolic pathway, not less.  There is an energy cost to doing more so there has to be a significant benefit or the organism will not compete reproductively.  We do not know of any epigenetic changes to DNA itself that allow doing more rather than less.  Methylation turns gene functions down or off not up.  So, are there kinds of epigenetic changes possible to DNA that would up regulate genes?  In genetics the answer usually is if you can dream up some weird idea if you look long enough you are likely to find an example.  So, maybe someone on here will get insprired and look long enough and find something akin to Barbara McClintok's jumping genes in corn and win a Nobel prize.  But, if anyone cares to put money on that I get the it ain't going to happen side.
Dick

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