Your misplaced confidence that Type II diabetes is a lifestyle disease for which you can just judge the victim is questionable.

I have never been overweight, I eat healthy (mostly plants, very little refined carbs), and I am active and run 5k regularly. That didn't prevent me from inheriting T2 from both my parents by the time I turned 60.

I'm pretty certain T2 was widespread 50 years ago. We just didn't test for it and people just lost their feet or went blind or had heart attacks as they got old. Was there even an inexpensive, rapid test for HbA1c in 1975?

If your read carefully, you'll note that I said largely. There is clearly a genetic component and non-lifestyle environmental factors.

You don't need to go back to the 1970s even. In 1990 fewer than 5% of Americans had Type II diabetes and now that number probably exceeds 15%.

A lot of them are probably not copying errors but errors in which parts of the genome are turned on and which parts are turned off.

(Agree entirely about type 2 diabetes.)

Sure DNA methylation can also just happen for any number of reasons.

I don't methylation is the only mechanism for that.

Also a lot of environmental factors that can cause cancer are out of your control if you live in an urban area.

The cancer rates are relatively comparable in urban vs rural zip coeds in the US[1].

[1] https://pubmed.ncbi.nlm.nih.gov/38801414/