This is just a personal theory, no real meat (pardon to pun) to back it up...

In the long-long-ago time all of the early civilizations were very close together proximity wise. As different religious theories grew they regularly traded back and forth ideas and practices. Sacrifice may have just been another practice that had been practiced for so long that the judaic religions just adopted it by for no greater reason than everyone was already doing it, so they just kept on doing it.

Sure, it may have eventually been transformed into a tool for the church to acquire meat, but considering those times I'd say it's likely that the birth of the idea of sacrifice wasn't founded with any ulterior motives. But like most things organized religion found a way to profit off of anything that provided opportunity.

As in, once-upon-a-time you could perform your own sacrifices. Then you needed a priest to do it for you. Then it had to be done in a "holy room", which incidentally was out-of-sight. There are actually recorded cases of priests taking the sacrifices and not even killing them... just takin them out the back door and shuttling them off to their private herd.

Nifty.

I think most religions have had some sort of sacrifice along the way. Sometimes animal, sometimes human and sometimes ritual. Some religions still proscribe the ritual killing of animals to be fit for consumption by the faithful.
Maybe the animals were shuffled out the back door because a lack of refrigeration prevented slaughter until needed. :D