This article is not meant to serve as nutritional advice and not intended to promote the eating of meat, nor is it implied that the author eats meat or recommends such. For advice regarding nutrition, please consult an independent expert.
Australopithecus, an ape-like creature and ancestor of humans, was originally a herbivore. Between 2.5 and 2 million B.C., forced by drought it started eating some meat to supplement its diet, probably by picking up small crawling animals and scavenging (so not necessarily by hunting initially) and it is thought the extra nutritional value of (and/or certain substances in) the meat allowed Australopithecus' brain, and therefore intelligence, to grow over generations, resulting in the first human, Homo erectus, around 1.8 million B.C.
More precisely, in this period of drought Australopithecus split up into two variants: One is called "robust", and followed the strategy of eating thick dry leaves to survive in dry conditions. The other is called "gracile", and it is this second variant that ate meat, and as a result underwent an unprecedented growth of its brain, allowing more intelligent forms of behaviour, including the making of stone tools, at which point they became of the genus Homo. These first tool-makers are called Homo habilis, and the successor thereof Homo ergaster. Then followed Homo erectus, with a cranial capacity in the bottom range of current humans.
Important is that brain cells require very much energy compared to other body cells, and therefore a large brain as typical for the genus Homo could perhaps not have evolved or been sustained on a herbivorous diet, if only because vegetable food did not contain enough energy (note there was no bread, pasta, cornflakes or the like in those days to provide energy; energy-rich starch foods came much later, with agriculture).
This implies that eating meat is what caused human intelligence, and thus humans, to come into existence, and that even the earliest real humans (Homo erectus) ate meat. But then, the brain works on glucose, a carbohydrate, which can not be derived from meat, so meat can not have been the direct energy source of the brain, but rather an addition to vegetable food in times of famine or starvation, or to increase total energy intake. The fat attached to the meat can have functioned as brain food though, since the brain can work on ketones, which are derived from fat.
Relevant too in this respect are archaeological findings showing that caries (tooth decay) occurred much in groups of humans whose diet contained grains, and very little in those who mainly ate meat. This suggests that humans were eating meat before they started eating grains.
Some vegetarians say humans were originally herbivores, based on a number of physical features we share with other herbivorous animals. They are right in the sense that our ape ancestors — the genus Australopithecus — were herbivores. Actual humans — the genus Homo — never were. Meat-eating and having a big brain with human intelligence have gone together from the start on. On the other hand, it must be said that the human teeth and digestive tract have always remained like those of herbivores, suggesting that meat was at best an addition to a plant-based diet.
The largest brains in human evolution were those of the Cro-Magnons, who were European ice-age hunter-gatherers. Meat is an major source of nutrition in the hunter-gatherer diet. The second largest brains, incidentally, were those of the Neanderthals — also hunter-gatherers — whose diet consisted mainly of meat. Current Western Europeans, according to recent D.N.A. studies, are largely descended from European ice-age hunter-gatherers, but their brains are about 300 cc smaller. This reduction in brain volume must have taken place after the transition from hunter-gatherer to agricultural diet; in the latter, carbohydrates from grain products, potatoes, rice and the like form an additional major source of energy that did not exist before the invention of agriculture, thus reducing the need to eat meat.
This does not mean it is wrong to stop eating meat in individual cases. Being vegetarian or vegan does not seem to have too many bad effects, and nowadays with agricultural and industrial technology we can make non-meat foods that contain any nutrients we need (except that we have no idea which nutrients we need, and except that some vegetarians are inclined to a "natural" life style and thus confronted with the paradox that a healthy vegetarian diet is only possible thanks to the use of modern technology). Although one could wonder about the warped beliefs, violence and terrorism of some animal rights activists, who of course do not eat meat. It is probably not caused or worsened by their diet — more likely is that rigid, obsessive-compulsive individuals who like to live by strict schedules feel attracted to especially veganism because of its simplicity and the ease with which it can be fitted into a scheduled life — but we can not exclude that possibility entirely yet.
Long after writing this article I was in the local supermarket named after a large four-legged animal with a trunk, when I saw a young man and woman at the coffee machine. They were apparently not buying anything but only there for the free beverage. The man uninterruptedly stared at me with an angry, aggressive, hateful look on his face, slowly turning his head to follow me with his eyes as I passed the two. He did not speak.
When I left the building, the same two people were standing on the street corner as if waiting for me. When I passed them, the man stared at me again, and after I had left them a few metres behind me began to speak loudly: "Yes, I would stoop in shame too with all those pigs around here! Pigs! Pig head!" He went on like that, gradually raising his voice even more, until I was out of hearing range about 80 metres or so further.
In the days thereafter while running or cycling, I found messages on the pavement near various farms in the surroundings, spray-painted through a template, saying Pigs… you do not see them, but they are there. It dawned to me that the two must have been animal rights activists. And something tells me the man was a vegan.
It has been claimed that not the eating of meat, but rather the cooking (heating) of food has caused our brains to grow, as it enabled more nutrients to be absorbed. While the latter is in itself entirely correct, it in no way contradicts the role of meat-eating as explained above. The two processes took place in entirely different eras, with a million years between them. The brain growth related to meat took place 2.5 to 2 million years ago, the effect of heating food took place after the mastery of the fire by Homo erectus, which happened in many places independently, about a million to half a million years ago.
In recent years the following arguments have been proposed in favour of vegetarianism, or at least in favour of eating less meat and more vegetable food:
To 1., the following responses need to be given:
To 2., the following response is needed:
A general reply to both arguments 1. and 2.: The real question is whether or not it would be better for one's individual health to change to or toward a vegetarian or vegan diet. The answer to that question depends on which expert one asks, in other words is a matter of belief. There appears to be no objective and conclusive advice currently as to what we should eat to stay or become healthy.