It has long been thought, to sustain sufficient numbers for the large and sometimes growing demand for sacrifices by the people, dozens of ibis breeding farms (called ibiotropheia by Herodotus) were established, initially throughout the regions of Egypt, but later centralised around the main temples, each producing around a thousand birds for mummies annually. An examination of the mitochondrial DNA disputes this and suggests that not only were wild birds caught and added to the captive flocks, but that they provided the bulk of the supply. The mummified birds were often young and were usually killed by breaking their neck. The head and bill were often placed between the tail feathers, and a piece of food was often placed in the bill (often a snail). The particulars of the mummification ritual often differed. The mummies could be stored in ceramic jars, wooden chests or stone sarcophagi. Not all mummies contain whole birds; some (cheaper ones) contain only a leg, an eggshell, or even dried grass from the nest. Birds were given different burials according to their status; as pets, offerings or holy individuals. Special sacred birds were afforded special mummification, transported from their cities to the temples long after normal offerings were sourced from temple farm flocks, and honoured with more luxurious burial. Different regions in Egypt observed slightly different practises regarding the ritual beliefs. Ibis mummification started by at least 1,100 BC and petered out by approximately 30 BC. Although the numbers of burials peaked at different times depending on the region and temple, the rituals were most popular from the Late Period to the Ptolemaic Period. Mummified specimens of the sacred ibis were brought back to Europe by Napoleon's army, where they became part of an early debate about evolution. According to Herodotus and Pliny the Elder the ibis was invoked against incursions of winged serpents. Herodotus wrote: Josephus tells us that when Moses lead the Hebrews to make war upon the Æthiopians, he brought a great number of the birds in cages of papyrus to oppose any serpents. Due to perhaps a mistranslation of the Greek of Herodotus, before the early 18th century Europeans were convinced that these ibises had human feet. Pliny the Elder tells us that it was said that the flies that brought pestilence died immediately upon propitiatory sacrifices of this bird. According to Claudius Aelianus in De Natura Animalium, and Gaius Julius Solinus,