The Holy Bible is full of animal sacrifice. (Indeed some religions still practice the ritual slaughter of animals )
We did this when we became more”civilised,” replacing human sacrifice with animal life (although in some cases, as with the Wicker Man of the Druids, both species were consigned to the flames!)
When we became even more civilised we replaced animal life with plant life. Good incense (such as that from Baiedo Japan) is made purely from natural flora (roots, saps, balsams, woods…).