Since humans began dwelling on this planet, they've been eating animals. It's therefore genetic. Nobody can claim to be genetically vegetarian. The concept of vegetarian food arose and spread mainly from Buddhism which considers it wrong to harm or slaughter any animal.

Eating veggie food or meat etc has nothing to do with any religion. In all holy texts,you'll find that eating other animals is more or less justified. Even Hindus who profess to be vegetarians forget that their holy book, the Srimad Bhagwad Gita specifically mentions Lord Krishna as explaining there are 3 types of food- Satvik, Asatvic and Tamasik ( or food obtained by violence, meaning slaughter of animals. I mention Hindus here specifically since most of them claim that harming animals or eating flesh is "banned" by their religion, when that's not the case.

The use of meat as food can be found in the Holy Quran, the Holy Bible and other texts of major faiths.

Humans, for the sake of economics and ease, consume only those animals or birds that can be bred fast and in captivity. If we did not eat these animals, there could be a boom in their population. And, in case such animals...for example, a chicken, got bird flu....the consequences would be disastrous considering the millions of chicken that would be around. Or, the mad cow disease...

Humans need to eat animals ( including birds and fish) because they are a rich source of protein and other nutrients, are easily available and renewable source and affordable as well.

Please dont bring in issues such as cruelty to animals to justify vegetarianism. Even plants feel pain and have feelings...so, killing a plant is no less a sin than killing a lamb. Eating meat can cause cancer, high blood cholesterol levels etc. But that's also true in the case of vegetables. Health problems dont arise from food. They arise from unhealthy lifestyles.