You're misunderstanding what I'm saying. 150 years ago people weren't taking in nearly as many carbs as we are now, nor were they living as long.

Diabetes, as a disease, is the breakdown of the process of your body using insulin. This happens naturally, in everyone, but happens at an increased rate when people have foods high in carbohydrates.

So the comment that people are guaranteed is to say, "If we all lived 300 years, you'd eventually have diabetes", not that everyone gets it, period.