Theories of the origin of life on Earth
There are different answers to the question of how life began. According to religious and philosophical views, life results from divine creation; this is a matter of faith that cannot be tested by experiment, so science does not assess it and treats such views with respect. Science studies natural causes through hypotheses that can be tested. In ancient times people thought life arises spontaneously (maggots from rotting meat, mice from mud), even Aristotle held this. F. Redi (1668) left some meat jars open and others covered with gauze and showed that maggots appeared only in jars where flies could lay eggs. L. Pasteur (1860s) proved that boiled nutrient broth in long swan-neck flasks stays clean: under present conditions life comes only from life (biogenesis). This discovery underlies food canning, pasteurisation and sterilisation in medicine. The panspermia hypothesis (S. Arrhenius, V. Vernadsky and others) holds that life may have been brought from space; this only moves the question elsewhere, because how life arose there is not explained. The basis of present scientific hypotheses is chemical (abiogenic) evolution: on the ancient Earth simple organic substances formed from inorganic ones and became more complex up to the cell. Part of this hypothesis has been tested by experiment, but exactly how life arose is still an open field of scientific research.
“Design the experiment”: groups redesign Redi’s experiment with their own materials (in writing only, no experiment is done), identifying the control.