>Your comments about what "people" were designed to eat also sounds pretty ignorant, since we're not genetically homogenous for starters. ...
Source for this? I don't doubt that there are groups with genetic adaptations to food (eg. genes for lactase persistence), but I'm not aware of anything for carbs.
It's not about a specific gene that says "you can/can't digest carbs" rather it's many variants of metabolic genes that dictate what hormones get triggered and what pathways get upregulated in such a way that eating carbohydrates causes fat gain/causes thermogenesis.
Source for this? I don't doubt that there are groups with genetic adaptations to food (eg. genes for lactase persistence), but I'm not aware of anything for carbs.