Dissect a cow and human cadaver on the living room floor, to demonstrate the extensive differences in colon sizes and organ structures (such as the rumen). Form follows function.

Ok, so that still might not convince him - but it would be funny to see his face though, yes?

Seriously though, if he is willing to accept TV show material like that so readily and absolutely, you are probably facing an uphill battle.

Perhaps the TV show relayed information about distant human relatives (2 million years back) which were primarily frugavore? Even chimpanzees eat meat from time to time.

The most notable explanation for meat eating is relayed by simple examination of the human gut. The smaller colon means less ability to digest fibrous plant material through bacterial fermentation, leaving a more extensive small intestines to handle meat and such.

Everybody knows that they used to hunt everyday, they also made the cave paintings showing their everyday life style...It's an historical fact... Good luck on it

Have him watch Cordain's Origins and Evolution of the Western Diet lecture. He makes a pretty solid case.

Beyondveg.com generally has some good information.

Paleolithic Diet vs. Vegetarianism

Cows eat 30-70 lbs of dry plant matter per day, which can be 100-150 total lbs depending on moisture content, according to what I found on the internet. I would be impressed if a human could eat 10 lbs of plant matter, even including moisture. Even if it were possible for humans to eat like cows, who would want to? They spend pretty much their entire lives chewing and re-chewing their food. I prefer eating steak and being done with my day's eating in 30 minutes, so the rest of the day I can be living life without toting around a 30 lb bag of green vegetables.

You could just hand him an anthropological textbook. 5.6 million years ago our ancestors probably WEREN'T eating any meat, but by the time these strange primates became close to humans, there is plenty of evidence from isotopes and butchered animal bones. The expensive tissue hypothesis also provides a rationale for why it became so importnat. There is no anthropologist who would dispute this and it's right there in any anthropology textbook worth its salt.

As for cows, we are NOT ruminants. We do not have four stomach compartments to do that kind of work. What we do have is a large hungry brain that needs a high-quality food like meat as fuel. Cow brains? They aren't very bright and their brains are quite small.

Its easy, go to a local forrest and see whats there is to eat. Here when i go to wilderness. Theres tons of mushroom, berries, herbs, some roots, deer and some game birds etc. I can image how much more of everything there was before. Never seen a tree there that grows bread, thats for sure. But maybe i am not picking up the right mushrooms :D

Look at out digestive system, our teeth, anthropological evidence of weapons and tools. I think we can confirm that we hunted, and ate what we caught. Except for when animals and game were scarce, it was likely a big portion of our daily calories.

This cant even be argued without ignoring huge amounts of evidence to the contrary. Does it mean we -never ate more than 50% of out diet in vegetables? No, I imagine that durign scarcity we are what was available and ate as much as we could find. Meaning, I am sure, that sometimes we -only ate meat, and sometimes -only- vegetation.

Meat is probably ALL we ate:

http://tinyurl.com/3jqbmuo

The guys hunted, the gals gathered crawdads, until Evil Eve ruined everything.