The fructose is identical, whether it is produced in corn and ends up as HFCS, or it is produced in flower nectar, fruit, or other plant tissues. The biosynthesis is pretty much the same in any plant.
Naturally occurring fructose is almost always complemented by a good mix of some of the 20 or so other sugar forms. (ribose, xylose, mannitol, etc).
Excuse my bluntness, but that's not relevant. No one eats pure fructose; it is always mixed with other ingredients. The enzymes that convert fructose to glucose in the body don't care about what is mixed with the fructose; they act on the fructose, and only the fructose.
You make a good point about epigenetics being a “later” process. But if it does turn out to be epigenetic-related, we are looking at the newborns immediate environment, which points to the womb and possible habits/lifestyle choices of the mother.
To expand on my epigenetics hypothesis: it is likely that we'll find gene variants that, have an epigenetic modification pattern that is different between normal and autistic children, even though the gene itself is unchanged. It would be like this: ATAATCG versus ATAATCG, where the letters in bold have been epigenetically modified, but the letters are the same. So a child could carry five gene variants that predispose towards autism but be normal because none of them happened to be modified epigenetically. And *none* of those epigenetic modifications would have happened in the child; they would have happened in the ovaries or testes of the parents. It takes years for epigenetic changes to accumulate; the time between conception and toddlerhood is just too short. (That is, the damage is done before the child exists.)
Whatever it is, it is interesting, and I’m not smart enough to say for sure one way or the other.
I try to keep an open mind about things, that’s all.
Just be careful. There are all kinds of pseudoscientific quacks out there, some of whom even have some sort of scientific training and know the language. There are ways to tell between genuine science geeks (such as myself) and quacks. One of those ways is that the quacks will often be trying to sell you something. They'll also be spouting all sorts of conspiracy theories (theory with the layperson definition, not the scientific definition, which is a different thing). An open mind is great, as long as you avoid the quackery.
I understand your epigenetic hypothesis but don’t totally buy it.
developmental damage can occur to the child in the womb that was not an inherited factor.
Caused possibly by malnutrition of the mother.
Look at FAS (fetal alcohol syndrome).
Look at the role of folic acid in preventing spinal bifida, clearly a developmental dysfunction that was not inherited, but is genetically regulated.