Hmmmmm.........so you don't think that going from eating a handful of sugar a year to over 12lbs a year will effect your metabolism? Interesting. So why is it that we can correlate the birth and sharp increase of:
Heart Disease
Diabeties
Cancer
with our increase of sugar intake over the past 100 years? Many diseases were not documented until 10, 15, 20 years after we started making such drastic changes to our diets. Mainly the introduction of coke and food processing. Look at the problems that Italians have as a whole and compare them to the French.
The problem is not carbs so much (as whole wheats, grains, etc). The problem is that many diets are high in carbs that consist of simple sugar and junk food that are coupled with hydrogenated oils and trans fats. We all know that i'm a fan of low carb simply because it works great for me, but i don't think for a second that high carb/low fat diets are bad. Our current pyramid scheme is a good one i think, but its designed for the person who exercises and doesn't eat a lot of crap. I didn't really start to gain weight until i started "trying" to follow the pyramid scheme, emphasis on "try".
It shouldn't take "millions" of years to effect our metabolism and other chemical functions. That should be evidenced by diseases like diabetes, heart disease and hypoglycemia that we have now that weren't observered until resently. Which, for me, my signs of hypoglycemia are purely dietetic. I've had zero problems with it since i started low carbing.
Granted, people may not have known what certain "modern" diseases were 200 years ago, but they sure as hell were cutting into cadavers. For century's man has been dissecting himself

I think its amazing to watch overweight, insulin dependant diebetics to go from being so unhealthy to improving themselves by what? Changing their diet and slowly cutting back on insulin *with their doctors aid*, increasing their exercise time and in turn slimming down and no longer needing to shoot themselves with a needle every day. Modern Medicine can't do everything, sometimes it takes a real lifestyle change on our parts to get where we need to be.