The ancient Hebrews, like their neighboring tribes in the Fertile Crescent, practiced human sacrifice in order to appease their god. But they eventually quit. The story of Abraham being ordered to sacrifice his son on the mount is reflective of that fact but was also told as an explanation why human sacrifice was no longer needed. Animal sacrifice was deemed to be sufficient to satisfy God's blood lust.
At the time of the legendary Jesus, animal sacrifice was practiced in Israel. The various "Christ"
groups of the time also believed in the efficacy of animal sacrifice. For example, in Mithraism, a bull became the "sacrificial lamb" and in some cases initiates stood in a reservoir beneath the bull to be baptized in its blood thereby becoming a full member of the sect.
The Christ sect, as promoted by the apostle Paul, reverted to a belief in the efficacy of human sacrifice and Christians have honored that tradition in various ways up to the present day. Although the theology is inconsistent and confusing it basically evolved in this manner: Yahweh, the Hebrew god, sent himself in the form of a human, who was his "son," conceived by the Holy Spirit in a young Israelite girl who was already betrothed to a man named Joseph.
[How a "spirit" could produce human or human-like sperm is not usually addressed. A spirit is a spirit is a spirit, without flesh and form and could not impregnate a pomegranate much less a teenage girl.]
The "son" who later theologians insisted was actually Yahweh (God) in human form, is reported in the Gospels (which are not historical records but evangelical tracts created to give Paul's "Christ" a foundation in history, for Paul's "Christ" lived not on earth but in the first of his seven heavens) to have lived between one and three years, teaching and preaching, acting as a prophet, sometimes exercising Zealotry, inconsistent and often angry, petulant (killing the fig tree even though it wasn't the season for figs), and contradictory.
The story is a familiar one to most people in the western hemisphere, telling how the Jesus figure is hauled before an illegal Jewish court and condemned and then brought to the Roman governor, Pilate, who orders him crucified. None of this is historical, either, but the point is that before long the "Christ" people who evolved in the sacrifice-rich culture of the Mediterranean in the first and second centuries (C.E.) under the guidance and gradual dominance of the "orthodox" accepted the doctrine that Jesus (called now the Christ or Messiah or Anointed One) who was crucified by the Romans was the sacrifice the Hebrew god demanded for the sins of human beings. This notion was based on the prior belief (assuming also that Adam and Eve were real historical figures) that because Adam and Eve (the progenitors of the human race) had sinned, everyone was tainted with what was called "original sin." This, in spite of the fact, that even the ancient Jews had tossed the belief that the children are responsible for the failings of their fathers/mothers.
To sum up: Orthodoxy taught that everyone is a sinner and destined to spent eternity being tortured by fire in a place called Hell. [The development of the doctrine of hell is also interesting but that's for another time.] The ONLY way that God can forgive our sins is by a human sacrifice, ergo the sacrifice of Jesus on the Roman cross.
In the later view developed by protesters in the Middle Ages known as Protestants, that sacrifice is a one-time thing, its efficacy made available by those who believe this story and accept God's love and forgiveness and try to live holy lives. The Roman Catholic Church, disagreed vehemently, for they from early on had developed (probably borrowing from Mithraism) an act of worship which was known as the Eucharist and then the Mass in which Christ is offered up for sacrifice each time the mass is performed. Followers of Romanism receive the benefits of that sacrifice each time they partake of the bread and wine in the mass, for the bread and wine become the actual body and blood of Christ when the priest says the magic words.
The point is this: human sacrifice is still the central salvatory act for the human race in the Christian religion in whatever form that religion is practiced. Without the sacrifice of Jesus on the cross there is no Christian religion.
Again the theology behind all this is incredibly murky and can be swallowed only with a huge dose of mythical castor oil. Jesus is not just God's son, says the writer of the Gospel of John, he is God himself, the creator of all that exists. So, the so-called human crucified on the cross was not a human at all but God himself. [God, of course, is without gender but is usually referred to as a "he".]
Furthermore, if God was on the cross, then he couldn't die because God can't die, nor can he experience pain as that is beyond God's purview and he would not need to be raised from the dead for he never died in the first place. In the end, the circle closes here: God sent himself into the world by being born from the womb of a Jewish teenager after being artificially inseminated by God himself (for the Holy Spirit is also God). He walked around the ancient ground of Palestine for a few years, healed a few people, did some other miracles, told some interesting stories, but sometimes ignored the needs of people and was downright mean to his mother and family. Evidently he made the Jewish leaders angry and they hauled him to the Roman ruler who ordered him crucified which was done, but shortly thereafter God appeared again on earth only in a more mystical form and then was whooshed up to heaven after promising he'd come again and make everything right, something he failed to do on his first trip.
That mythology still reigns. Christians of whatever stripe insist that Jesus' death on the cross was and is essential for salvation (getting into heaven). In Christianity, people would go to hell without the sacrifice of God's son on the cross, and will go to hell if they do not acknowledge this sacrifice and live by the rules God laid out so many years ago. Roman Catholics take all of this a step further by re-enacting that sacrifice at every mass and offering the opportunity for believers to participate in that sacrifice by the ritual eating and drinking of the actual body and blood of Christ.
Today there appeared in the Huffington Post an article telling about the finding of a skull which was probably from a human sacrificed according to the beliefs and rituals practiced by the Aztecs of Mexico some 500 years ago.
The article concludes with this sentence: "A formidable people, the Aztecs believed the sun god Huitzilopochtli required human blood in order to move the sun across the horizon [...] Sometimes volunteers would give themselves up for the honor, and other times prisoners were sacrificed.
Well, it is important that the sun moves across the horizon and if it takes human sacrifice to do that, so be it. A perfectly reasonable conclusion considering the fundamental beliefs of the people.
But I would be willing to bet that millions of Christians today would read that story and think of how awful human sacrifice was and what nonsense it was to think that the Aztec gods could be appeased by the offering of human blood.
