Cultures in which sexual activity is regarded as sinful or frowned upon by one of more of their gods often include virginity in the ritual so the best and most powerful effect is obtained by the blood sacrifice of a virgin, and best of all a human virgin.
This has lead to the notion that a god made angry by transgressing one of it's rules, or simply by not worshipping it enough, or in exactly the right way, or even by just being born and existing, can be persuaded to forgive that 'sin' by a blood sacrifice.
The earliest accounts of human sacrifice cannot be distinguished from myth with any certainty but the existence of those myths in the first place with their assumption that human sacrifice to appease or simply to please gods, is indicative of a cultural assumption and a vestigial belief.
According to Roman historians, the Celts of Europe, including the British Isles practised human sacrifice. This is supported by archaeological evidence. It has also been suggested that the 'sacred groves' of Druids, rather then places of natural beauty where one could be as one with nature, as is romantically assumed, may have been fearful places of human sacrifice where human body parts were hung up as offerings; a grotesque tradition which may have an echo in dressing the Christmas tree. See Kingdom Of The Celts by John King.
There is evidence of human sacrifice during early Greco-Roman times. The god Artemis saving Iphigeneia, who was about to be sacrificed by her father Agamemnon, by replacing her with a deer, may be a version of the Abraham and Isaac myth of the Hebrews where the deer has become a ram.
One form of human sacrifice, the retainer sacrifice, where a powerful person's servants were killed and buried with him, was common across Euro-asia from earliest times and was in some areas, an integral part of the comitatus system by which a ruler gathered a trusted band of supporters, often tied with blood rituals and oaths of personal loyalty. The comitatus system found it's way into early Islam following Islam's expansion into Central Asia. The stories of the putative Christian founder, Jesus, having a small band of loyal disciples may also be a form of this.
|Hawaii Human Sacrifice|
|James Cook Witnessing Human Sacrifice|
In pre-Columban America Mixtec, Aztec, Maya and Inca people all practiced human sacrifice.
And of course all three Abrahamic religions trace their origins back to a legendary Bronze Age nomadic tribal leader, Abraham, who according to tradition, seems to have accepted that it was perfectly natural for a god to demand a human sacrifice, albeit one which is stopped at the last moment. There is nothing in the legend to suggest that Abraham found the idea strange, or grounds for doubting the divinity of the voice he was hearing, so very clearly the culture in which the legend arose saw human blood sacrifice as a normal way to appease gods,
Later on, as the Hebrew legends develop there are accounts of the slaughter of defeated enemies being ordered by their god and of its demands that anyone who transgresses the more important of its 'laws' were to be killed to appease it or its wrath would be visited on those who had allowed the sin to go un-punished. This is still to be found in the religions which have evolved out of this primitive Bronze Age legend.
And of course there is the Hebrew scapegoat tradition where the sins of a people can somehow be transferred to an animal which is then ritually sacrificed to the god who then forgives the people for their 'sins'.
And finally, we see the blood sacrifice represented by the death of the legendary Jesus of Nazareth, an act which even today followers of that tradition believe somehow 'saved' them from the wrath of the very god of whom the sacrificial victim was supposedly a manifestation. What sacrifice could possibly better the blood sacrifice of a mere mortal other than the blood sacrifice of a god itself, and a virginal one at that? You will still even hear people today claiming their 'sins' have been 'washed away' by the blood of Jesus as here and here.
In 1099 when Crusaders captured Jerusalem after a long siege, they ritually slaughtered all the Moslems and Jews who had defended the city, so the the city was said to be 'knee-deep in blood'. When Saladin re-took Jerusalem for Islam in 1187, in order to contrast Islam with Christianity, the inhabitants were spared and the former Moslem holy sites were restored and 'cleansed', not by washing them with sacrificial blood as the Christians had done, but with rose water.
A more recent example of the blood sacrifice can be found in Irish history. It is said of the Irish patriot Patrick Pearce:
"For Pearse, the idea of a blood sacrifice had additional appeal. Even as a child, he had unusual fantasies of self-sacrifice for his country, derived from Celtic myths and religious writings. He later fused together his nationalism and his Catholic faith. His Christian devotion had always centred on Christ’s Passion and Crucifixion, and he gradually developed a consuming yearning for martyrdom, in conscious emulation of Christ’s sacrifice on the cross. He wrote: ‘One man can free a people, as one man redeemed the world’.Pearce led the 'Easter Rising', the timing of which was probably deliberate, and was executed for his part in it, as were thirteen others, in an act by the British authorities which resembled ritual sacrifice and which turned Irish popular opinion even more solidly behind the revolutionaries. The 'blood sacrifice' had worked, but not in some magical, mystical way, but by public revulsion at those who had carried it out.
Pearse was also influenced by a mystical belief in the assumed benefit to mankind of blood spilt in violent conflict. He wrote in 1913: ‘Bloodshed is a cleansing and sanctifying thing'".
Strangely, in all of this there is never any explanation of just how a blood sacrifice works. It seems to be something buried so deeply in the primordial human psyche that some people just assume it's so obviously true that it requires no explanation. It has been said that the frequent calls for the death penalty for particularly heinous crimes may be a demand for a blood sacrifice and that the burning of heretics and witches were forms of it.
Obviously our memes have picked up some strange mutations during their long evolution, and, as one would expect of a parasitic memeplex, it's component parts serve the needs of the meme, not their host. Possibly these demonstrations of power by a ruling and priestly class came to be accepted as having power in their own right; that rather than being demonstrations of power, the acts of human blood sacrifice was actually the source of their power.
Clearly there are people who are still infected with a memeplex which includes the acceptance of the magical power of blood sacrifice, although they will usually recoil in horror at the thought of followers of other gods, or people from earlier, less civilised times, practising it and yet their religion would not have gained any traction in a society in which the idea of human blood sacrifice was unknown or abhorrent.