Although I have no reference available for this, I have read that the ancient oracular practice of examining animal's intestines was similarly manipulated and c

Although I have no reference available for this, I have read that the ancient oracular practice of examining animal's intestines was similarly manipulated and contracted for. The priests knew that some plants (containing teratogens) created mutant offspring whose insides (if they lived at all) would be messed up. By feeding some animals those plants, they could offer up either a bad omen or a good omen (regular animal, normal intestines, liver etc) at will as their leaders wished. Because teratogens were beyond the imagination of the ordinary citizen, it had to be the Gods' speaking, 'cause they usually did give pretty good advice.