It's not just sugar - any carbohydrate which a bacterium can easily metabolize to sugar (i.e. most of them) is a hazard. Grains, tubers, etc. are all dangerous from a dental perspective and have only been consumed in calorically significant quantities after the advent of agriculture.
You're correct that any carbs can help form plaque, but humans have been getting significant numbers of calories from them since before we were H. sapiens.
This is only plausible for humans in tropical areas. It does not stand to reason for humans north of (conservatively), say, 40º. Even in humans in areas with calorically significant quantities of carbohydrates available, fossil records suggest they probably preferentially ate ruminants, same as anyone else.
Most of human evolution occurred below 40N, so even if that point were correct, it would at best be limited to the adaptive behaviors of a very small group of human ancestors.
However, there's plenty of evidence suggesting that there wasn't any such regionally adaptive behavior. The original find that suggested starchy plant consumption in H. erectus was analysis of the Dmanisi fossils at ~41N. Later work tying these sorts of results to typical European Neanderthal diets has been done for North Sea sites (~50N). Of course, Neanderthals never went much farther north than that due to the climate. As for AMHs, I've seen papers of sites near Smolensk (~55N) indicating moderate to heavy starchy plant use. That's not far from the glaciation line.
Moreover, there are fairly convincing arguments that a nearly pure-meat diet doesn't work in winter due to the general lack of fat (e.g. https://doi.org/10.1016/j.quascirev.2009.11.016 ). There are caveats and workarounds here, but this whole idea that high-latitude hominins had limited, homogeneous diets is on increasingly shaky ground.
They are only dangerous if you don't brush or floss. With respect to ancient cultures a little twig is a damn effective dental cleaner and about as good as a modern toothbrush.
People today who brush regularly still have way more rotted-out teeth than people who didn't eat significant quantities of carbohydrates. They are dangerous even if you brush.
Growing up, my dad often said that raw carrots are "nature's toothbrush" and he would encourage us to end any picnic lunch with carrot sticks, not with a sugary dessert. Can carrot sticks function like a little twig in terms of knocking undesirable food gunk off teeth?
Anecdotally, I don't consume a whole lot of refined sugar but any time I do, I can feel the plaque building up almost immediately. But at least in terms of apples and grapes this isn't the case, nor does it appear to be so with complex carbs including bread and potatoes. Additionally I've noticed most candies and soda tend to leave residual taste in my mouth for hours. So I'm partial to pointing the finger specifically to refined sugar.
I think you mean tarter, not plaque. Plaque takes a while but you obviously will feel tarter only teeth at the end of any day if you've had sugary or carby foods. White bread starts breaking down into sugar as soon as it hits your mouth due to enzymes in saliva.
Are you sure? My wife is allergic to corn syrup, and we find it in EVERYTHING. 95%+ of spaghetti sauce, even in canned vegetables. It's surprising how sweet things are these days. Our standard for starting a new recipe is to cut the sugar by 1/2 to 1/3rd, that way you can taste the other ingredients.
Even buying tea is tough, many are very sweet. Sadly the sugar lobby has been successful in blocking imports, setting price floors, and generally keeping sugar higher priced than corn syrup, which from what I can tell is worse for people's health.
In my family its as clear as day. The boomers in the family grew up on soda and all have had dozens of cavities and currently sport gold teeth. Not the case for the older generation who grew up in the great depression off of water alone, or the children of the boomers who were raised better than a constant supply of 7 up as the only source of liquids.
Abundance of sugar in modern diets maybe to blame.
"Intake of added sugar, particularly from beverages, has been associated with weight gain, and higher risk of type 2 diabetes and cardiovascular disease. Natural and added sugars are metabolized the same way in our bodies. But for most people, consuming natural sugars in foods such as fruit is not linked to negative health effects, since the amount of sugar tends to be modest and is "packaged" with fiber and other healthful nutrients. On the other hand, our bodies do not need, or benefit from, eating added sugar. https://www.health.harvard.edu/blog/are-certain-types-of-sug...