Animal sacrifice is an ancient practice that goes all the way back to prehistory. To understand how and why the offering of living things were made to deities you have to understand what those deities represented to those ancient peoples.
Left to their own devices, primitive people were shockingly warlike, and agriculture only made it worse in many many ways. The lion’s share of the harvest went to the army once labor specialization became a thing. At least one enormous battlefield was discovered in what is now Northern Germany where the dead are estimated to have numbered around a thousand.
Imagine living in these ancient times. Today there are endless forms of entertainment to sink your boredom into. Even before technology and the Internet, there were books to read. Read enough of them and you can consider yourself educated.
The ancient world had no books, which wouldn’t become possible til the Middle Ages. Lucky civilizations had access to papyrus, which was a form of paper that was cheap enough to be accessible to ordinary people. But in general, the main form of entertainment was people telling stories to each other.
Think a little bit about what it means to tell a story. To tell a story is to attempt to come up with a meaning, a reason, for why the events occurred. For an entire people to tell the same story with similar meaning each time is the act of creating culture. It was simply what people did in order to make sense of the things they had to do to survive.
These cultures reflected their societies. Warlike societies had warlike gods. Remember what it means to tell a story, to ascribe meaning to the seemingly meaningless, even if only for entertainment. But when all of society starts telling the same story about itself, suddenly it becomes more than just a story.
The meaning behind the story assumes greater significance, today we call it divine significance. It’s natural for humans to assume that meaning grander than the individual to still stem from a person-like source. Meaning greater than human conception, must have a greater-than-human source, because otherwise the stories eventually fail to make sense. And if all of society can agree on the larger meaning behind the things it has to do in order to survive, we now call that cultural agreement religion, and those greater-than-human personages deities.
Religions ordered the society of ancient peoples to an extent we could only today call mind-boggling. Ancient Egyptians demanded that Pharaoh build a pyramid tomb, and judged him on its size and splendor. We used to believe that grave robbers stole all the wealth in these tombs, but now we know the deceased Pharaoh’s family would regularly retrieve buried valuables.
The pyramids were thus a symbol of Egyptian wealth and power. Elaborate, beautiful, useless. As technology and wealth concentration allowed greater collection of resources, the pact made between the rulers and the ruled demanded ever grander splendor.
And so animal sacrifice became one of these beautiful uselessnesses. The Hebrews believed in three kinds of sin graded by severity. Sins of omission, of commission and finally of overt rebellion against God. It is only the first form of sin that can be forgiven through animal offering. But the offering isn’t the only thing that must be done to earn forgiveness. Sincere repentance, acknowledging that a sin was committed, and also restitution must be made to the person you sinned against.
Hebrew offerings could only be made at the place in which God dwelled. Before the construction of the Temple, this was accomplished at the Tabernacle, which was an elaborate mobile structure built to painstaking measure and ritual. The Bible recorded instances of God striking people dead for mishandling divine artifacts. Such is the power of belief. Many ancient cultures recorded divine laws that were punishable by death, and it wasn’t executioners that did the killing.
So why animals? For the same reason the Egyptians built pyramids, because doing useless things with expensive resources was seen as being pleasing to capricious larger-than-life beings with the power of life and death. Celebrations commemorating alliances and victories would involve the sacrifice of sometimes shocking numbers of animals.
Contrary to popular belief, the offerings were usually cooked and eaten, rarely just burnt. You had to be atoning for a very serious sin in order to be called on to completely destroy the animal. What made it expensive and useless was the fact that it wasn’t done for survival, it was out of the normal routine of life. To have a feast every single night just wasn’t practical. The Hebrews gave much of their offerings to the poor.
Hinduism is a term given to a dizzying number of ancient local customs / religions, some of which at various points practiced animal sacrifice, for the same reasons as in the West. The dynamics underpinning human behavior don’t change all that much, though the reasons given and thus the cultures formed do indeed vary largely according to geography.
However India’s fertile farmland caused it to develop huge civilizations very early on. Resource-intensive, useless, practices tend to get stamped out the larger the civilization gets simply because they need to preserve economies of scale rather than just throw away their excess resources.
The traditions still live, but the actual sacrifices being made nowadays are vegetarian stand-ins. Some hold-outs to this day still actually kill animals, but it’s pretty rare.