Unfortunately for the sake of our argument my proof is not very scientific but more anecdotal. However I will state a few things and you can refute them as you see fit. First and probably most scientific of my evidence is autopsy results. You will find that those who have clogged bowels and who are obese are those who are meat eaters. I dont know many obese vegans. Admittedly I do know some who appear to be underweight however and this can be just as unhealthy as someone who is slightly obese.
My second offering of anecdotal proof comes from myself and from some of my friends. I have eaten meat my entire life and will continue to do so. However, as I get older I find that I have a harder time eliminating the day after eating a large amount of meat. In particular, steak is a problem for me. If I eat a large amount of steak the day before I will have problems the entire next day eliminating.
"Please explain and how this is conclusively due to meat consumption (as opposed to refined sugar/carbohydrates, chemical exposure, aspartame etc, chemical in food etc)."
I simply cant. I dont believe that meat is the root of all evil either and is 100% responsible for the majority of health problems today. I am not even convinced it is responsible for say 25% of our health problems. The consumption of meat along with perhaps many other things such as what you are quoted as stating in the above passage could very easily be the problem. I dont blame meat alone. I believe a major problem with the North American diet is the consumption of refined sugar/carbohydrates. We have diabetes to thank for this. The amount of chemicals we put in our food is insane and the long term effects are not well understood.
I understand the point you are making about tools and how they have allowed us to consume meat. However, I think you misunderstand my point. I am willing to completely agree that the human being has physiologically adapted over time (the last 2.4m years as you say) to better consume meat. However, I believe that these changes are incomplete but that perhaps someday we will evolve to be able to consume meat like carnivors can but right now we cant. To my mind, the biggest limitation is how we eliminate. While the carnivor has the teeth to chew its meat to digestable sizes as we use tools to do this job, the carnivor also has short and wide intestines to easily eliminate waste which we do not. Yes I accept that man has adapted over time to be able to better consume meat but our transformation is incomplete.
I would like to say one more thing. Scientific proof is a funny thing. What is proven safe one day often is anecdotally shown to be unsafe the next and then finally scientifically proven to be unsafe. Take the example of Vioxx. How many years went into the scientific research of that drug to prove that it was both useful and safe? I believe the average drug takes 10 years to get approval from the FDA. 10 years of scientific proof went into proving the drug was safe to use and a few years of its use proved, anecdotally, that the drug was unsafe. Science will now explain why it is unsafe or what combinations of certain situations made that drug unsafe but science failed us from the very beginning. Now, having said that do I believe we should crawl back to the dark ages and reject all scientific advances? No. I just believe we cant afford to believe in science to always be right.
I suppose in short I really just do not trust science very much. I use it more as a guide but not as proof. I have a personal history where science (doctors) nearly killed me but even more recently they have helped to rebuild my knee. So I dont ignore science or believe it is without any use but I constantly question it and the value many place on scientific research. Perhaps this leaves us at a point where we agree to disagree.