I am going back over a hundred years, on both sides of my family - mother's side and father's side - spread over a vast area of England. We come from as far South as Devon and as far north as Nottingham. And I believe we have some Welsh blood, too.
One of my great grandmothers, who came from Nottingham, would be well over a hundred by now - I can't go any further back than my great grandmothers. We do not eat the same things she ate! Because that theory doesn't take into consideration location, income, tastes, - my great grandmother adored boiled tongue - I wouldn't touch it with a barge pole. My ancestors had a heavily meat-based diet - my paternal grandmother worked for a butcher! But my maternal grandmother was practically vegetarian. I myself have never liked meat very much.
Then, we have two world wars to take into consideration, which drastically changed things food-Wise in England. There were so many food shortages that people had to drastically alter their diets. Bread was out for a start! At least, where we lived when I was a child. Food was rationed, we had one egg per person, per week. And no sweets or chocolate.
However, when I was married, we were fairly well-off, so food choices changed again. My eldest son married a Vietnamese, so no way did he eat the same as me. Didn't stop him developping thyroid problems, though.
You might just as well say that all people in England eat the same. Or all people in France eat the same. Or that French people eat the same as English people - although that definately isn't true. But if it is true, then why are there people with Hashi's all over the world? You cannot possibly say that we all have the same food tradition. The highest incident of Hashi's is in Japan. What is the Relationship between my diet and a typical Japanese diet? There isn't one.
Sorry, but your theory just doesn't hold water. At least, not as far as I'm concerned.