Spontaneous generation is the debunked idea that life can, on a daily basis, arise from nonliving material. Abiogenesis attempts to explain how life on Earth began.
In modern science, it is understood that living things arise from other living things. This is cell theory; the knowledge that cells (the basic units of life) come from preexisting cells. But life had to begin at some point. So what is it that makes the discredited theory of spontaneous generation a fallacy and abiogenesis solid science?
Spontaneous generation is the belief that, on a daily basis, living things arise from nonliving material, and this idea was entrenched throughout most of recorded history.
Aristotle was one of the first to record his conclusion on the possible transition from nonliving to living. According to Aristotle, it was readily observable that aphids arise from the dew on plants, fleas from putrid matter, and mice from dirty hay; and this belief remained unchallenged for more than two thousand years.
In the 1600’s the first microscopes were crafted. These new instruments, pioneered by Robert Hooke and Anton van Leeuwenhoek, enabled scientific investigators to observe tiny living organisms that were previously unknown. Where did these tiny microbes come from? Did they generate spontaneously from nonliving material, or did microbes and other living organisms only arise from other living organisms.
The invention and refinement of microscopes heated up the debate over spontaneous generation, and spawned a slew of research, over the next 200 years, that would finally put an end to this idea.
Francesco Redi demonstrated that maggots come from flies, not from putrid material. Lazzaro Spallazani revealed that microbes could be eliminated from broth that was placed in sealed containers and heated to high temperatures, and Louis Pasteur, the French chemist and all around scientific overachiever, performed several experiments which demonstrated conclusively that life arose only from living predecessors.
Spontaneous generation was not a theory that addressed the origin of life, but instead, had been based on the belief that living things commonly emerge from nonliving matter. Although science ultimately established that living things arise from other living things, the question remained…”Where did the first living thing come from?” Abiogenesis is the theory that addresses the actual origins of life on Earth.
All living things have genetic instructions made of organic molecules called nucleic acids. These instructions are essentially the blueprint for each living thing. Therefore the question of how life on Earth originated, the investigation of abiogenesis, focuses on how the first nucleic acids came into being.
Fossil evidence and molecular biomarkers, such as carbon isotopes, show that microbes existed on earth 3.5 billion years ago. These cellular microbes were complete living cells, so the origin of genetic chemicals had to precede these live forms. But there was no solid theory on abiogenesis until 1924, when Aleksandr Ivanovich Oparin, a Russian biochemist, presented his ideas in his publication The Origin of Life. Oparin proposed a theory that life on Earth developed through gradual chemical evolution of carbon-based molecules within a primordial soup. Since Oparin’s significant contribution, scientists continue to investigate the specific sequence of chemical events that led to organization of the first nucleic acids.
* Sources *
Bauman, R. (2005) Microbiology. Pearson Benjamin Cummings.
Oparin, A. I. (1924) The Origin of Life. Moscow: Moscow Worker publisher (in Russian).
Park Talaro, K. (2008) Foundations in Microbiology. McGraw-Hill Companies.