This was the question posed by New York Times. Following is my entry.
Evolution, Health, Resource Utilization, Animal's survival, all require that we eat meat. I am touching upon these major reasons in this note.
Humans evolved from Primates. It is a very well established fact that eating meat and their fatty brains and marrow was a very crucial factor in the growth of human brain, which made us human. Humans evolved as omnivores eating meat and plants both. It is what we are. With time and tools we learnt to be a skilled hunter, and caused extinctions of a large number of mega fauna species. Later we learnt agriculture and domesticated animals which provided a stable source of food. This allowed us to stay in one place and form societies, and improve technology. Slowly with agriculture we started transforming the landscape, destroying forests and the livelihood of animals staying there to create agriculture farms. Now humans are so advanced and so much in control of the planet that the only way animals can survive is by hiding from us, or providing us some value. Yes they can be kept in small sanctuaries or zoos. The largest stock of animals in the present times are the animals that are used for food. If humans became vegans, we will render all these animals extinct, because they will not be required.
We are too many on this planet. To feed the whole world we should try to utilize as much solar energy as possible. This can be done by growing more plants and utilizing as much as is possible of it. When we grow plants there are many things that we cannot eat. The problem is that currently we are too fixated on grains. Through cereal crops we utilize only the seed part of the plant. The rest dries out before we can obtain the seeds. This is a collosal waste of energy. Instead we should use plants that give edible food while they are alive. The unedible parts of the plant can be fed to animals, and the edible parts can be eaten by us. The animals will convert the unedible part of the plant, into edible meat. This will maximize energy utilization. Also land that does not grow anything except grass can be utilized. Only an omnivore society can maximize utilization of the production of plants.
We have evolved as omnivores. The longest continuously vegetarian society is in India, which started only some 2500years ago. Veganism has only come into being since 100 years ago. Veganism more than vegetarianism requires technology to be possible. This in itself means its not a natural diet for us. Although we know how to make vegetarian way of eating sustainable for a number of generations, this experiment has still to go for several generations for veganism. There are no uncivilized tribes that are vegetarian. Yes we could equate being vegetarian with being civilized, but for me that is arrogance. It takes a lot of hubris to say that we are better than other animals, and the body that mother nature created for us, should have been created differently. We are not herbivores, we don't have the ability to digest cellulose, doesn't matter how much we may want to. Nor are we carnivores, our brain needs a lot more glucose than those small brained carnivore animals.
Lets remember our place in the world and be omnivores as mother nature intended us to be, for our sake and for the animals that feed us. Growing animals for food in a humane way is possible and is required of us as ethical humans.