Do Organisms Change by Natural Processes?

The notion that organisms may change by natural processes were not investigated as a biological subject by Christian theologians of the Middle Ages, but it was, usually incidentally, considered as a possibility by many, including Albertus Magnus,(1200-1280) and his student Thomas Aquinas (1224-1274). Aquinas concluded, after consideration of the arguments that the development of living creatures, such as maggots and flies, from nonliving matter, such as decaying meat, was not incompatible with Christian faith or philosophy, but he left it to others (scientists) to determine whether this actually happened.  

 

The issue whether living organisms could spontaneously arise from dead matter was not settled until four centuries later by the Italian Francesco Redi (1626-1697), one of the first scientists to conduct biological experiments with proper controls.  Redi set up flasks with various kinds of fresh meat; some were sealed, others covered with gauze so that air but not flies could enter, and others left uncovered.  The meat putrefied in all flasks, but maggots appeared only in the uncovered flasks with flies had entered freely.