Hinduism and Jainism teach vegetarianism as moral conduct whilst Christianity and Islam generally do not. Buddhism in general does not prohibit meat eating, while Mahayana Buddhism encourages vegetarianism as beneficial for developing compassion.
Humans, are they supposed to be vegetarians? Quotes from the holy scriptures:
"Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in that which is the fruit of a tree yielding seed; to you it shall be for food."
In Genesis (1:30)
"And to every beast of the earth, and to every fowl of the air, and to every thing that creepeth upon the earth, wherein there is life, I have given every green herb for food; and it was so."
"He that killeth an ox is as if he slew a man."
When Jesus spoke of meat he was talking of food Close study of the original Greek manuscripts shows that the vast majority of the words translated as "meat" are trophe, brome, and other words that simply mean "food" or "eating"
St. Luke (8:55)
"Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel. Butter and honey shall he eat, that he may know to refuse the evil and choose the good."
The Manu-samhita, the ancient Indian code of law, states, "Meat can never be obtained without injury to living creatures, and injury to sentient beings is detrimental to the attainment of heavenly bliss; let him therefore shun the use of meat."
In another section, the Manu-samhita warns, "Having well considered the disgusting origin if flesh and the cruelty of fettering and slaying of corporeal beings, let him entirely abstain from eating flesh."
More recently the Hare Krishna movement has introduced these ethical considerations around the world. Srila Prabhupada, the movement's founder-acarya (spiritual master), once stated, "In the Manu-samhita the concept of a life for a life is sanctioned, and it is actually observed throughout the world.
Emphasizing the Vedic conception of the unity of all life, Srila Prabhupada then stated, "Everyone is God's creature, although in different bodies or dresses. God is considered the one supreme father. A father may have many children, and some may be intelligent and others not very intelligent, but if an intelligent son tells his father, 'My brother is not very intelligent; let me kill him,' will the father agree? ... Similarly, if God is the supreme father, why should He sanction the killing of animals who are also His sons?"
The Quran, 6:38
All creatures on earth are sentient beings. "There is not an animal on earth, nor a bird that flies on its wings - but they are communities like you."