Abstaining from meat eating or eating a vegetarian diet has been given many interpretations in the light of religious, ethical, moral and medical reasons. For a moment lets step away from these traditional and contemporary view points and approach this issue from a rather different and interesting angle, which looks more compelling. (at least to me)
Mankind is absolutely dependent on vegetation to meet the entire nutritional requirements. Plants are the only producers of energy. The produce their food by means of a photochemical process called as photosynthesis. All other living creatures in this earth are dependent on this energy either directly or indirectly and the same energy flows through different levels.
As a thumb rule, when energy flows across different levels, only 10% of it is transferred to the next level. The graphic below represents what is known as an ecological pyramid showing the energy transfer rates across various levels.
The amount of energy possessed by the primary consumer for instance, a goat is 1/10th the energy possessed by the producer i.e. the plants. In other words, if a given amount of plants could support 100 people and if people are eating goats instead, only 10 people can survive because the energy transfer from plants to goats is only 10%. To make it even simpler one can say that if 1000 calories are available from plants directly, only 100 calories are available from the goats, which feed on the 1000 calories. If people are vegetarians or dependent on plants alone then a larger number of people can be supported with the available resources.
This could be the true rationale behind having vegetarian food habits or abstaining from eating meat, given the fact the human body and the biological systems within it are well adapted for meat eating.
If eating meat was not good for human health, why in the first place is our digestive system equipped to digest them and why do we have ‘canines and incisors’ tooth that are designed for cutting and tearing meat? Often people fail to differentiate between eating and over eating.
On the other hand we need to take into account the scientific advances which mankind was able to achieve. From a subsistence agriculture that was largely dependent on the forces of nature for water and essential nutrients, agriculture today has gone to different levels. Even barren lands can be cultivated these days. Commercial and intensive agriculture has its downsides too but thats a different story altogether. The fact of the matter is that dependency on plants has been brought under control, at least in theory.
The second but not so important reason for avoiding meat could be the disruption in the food chain it might cause. The food chain is an intricate inter-linkage between different organisms in the process of energy flow. Even if one component of the food chain is altered in numbers, then the upper levels might not get enough food while the lower levels might over grow thus leading to chaos. Given the fact that consumable meat is grown on an industrial scale the problem of disrupting the food chains seems to be invalid.
Its all about the individual's choice and conscience when it comes to the question of eating meat because both the arguments seem valid. Evolution of species guided by the survival of the fittest theory is the one which has shaped all the living organisms and one of the basic principles of the survival of the fittest story is meeting the nutritional requirements. Deer, which is long believed to be a herbivores (yes thats what most of the schools teach, at least i was taught so) may not be one anymore. There are evidences caught on camera about the Red Deer in the Scottish Island of Rum eating the head and legs of live sea birds to meet the calcium requirements so that it can grow its antlers better, which is the sign of a healthy male. The size of the antler plays a significant role in the choice of mate/healthy male for reproduction. If this practice gets coded in their genes, there may come a time when the deer eating the sea birds would become a part of their food habit and it may not be called a herbivore.
PS: The dear story is true. If interested, it may be checked here.