There is a lesson in Archaeological discussions that: if the human race were wiped out, and 1000 years later others would arrive from another planet, see the Christ on cross imagery, and translate some of the text about Heaven &c, they'd likely think Christainty was a 2000 year-old cult that sacrificed people on crosses so that they could get to the afterlife. At least in Soylent Green the old people became food. In any event, I think it's terrible practice to sacrifice people. They're also not tasty, or so I've read.