The Formation of Life in the Universe:
Life from Non-Life
Author: Sara Cole
Wayne State University
Astronomy2010 - Dr. Claude Pruneau
Both classical and modern science have striven to determine the origin of life. Some Many thoughtful contributions to the study of life’s origin exist, but none are easily testable. It is generally agreed upon that life came from non-life: research still ambitiously seeks to discover exactly how.
The origin of life is a question at the center of a web of studies. As a result of the marriage between man’s sense of self and his cognitive faculties (both fittingly enabled by the evolutionary process), man has been able to not only ponder on but also uncover the scientific truths about the origin of life. How did living matter come from non-living matter? In what conditions did it form? Although not yet able to recreate the exact conditions nor reproduce the precise moment of transformation in the laboratory, many viable hypotheses exist about the origin of living matter. Several studies examine important aspects of the origin of life: the probable conditions, the probable materials, and the probable cause – whether it had been a “spark”, or a gradual process – that allowed for life to come about. What can be said about the division between non-life and life, and the origin of this division?
The Definition of Life
Physicist Erwin Schrödinger elegantly postulated that life is that which “avoids the decay into equilibrium” , basing his definition on the fact that that every known, non-living, physical type of matter in the universe equalizes itself with its surroundings over time – hypothetically and ultimately leading to a universe of total uniformity in temperature and structure in a process called entropy. Living matter has been observed to postpone this process by taking in and metabolizing nutrients, as well as propagating itself through reproduction.
This process distinguishes that matter from that which is non-living. Erwin Shrodinger, although a physicist by profession, concerned himself with studying the link between physical matter and living matter. He is famous for Shrodinger’s Paradox: in a random world, organisms continue to exist and grow by importing high-quality energy from outside their bodies (for example, energy from the sun). They increase their order at the cost of higher entropy around them.
Other scientists propose similar definitions: all of which refer to some qualities of the terrestrial life that observed on Earth– for example, matter may be classified as living if it is self-propagating, capable of metabolizing nutrients, capable of reproduction, comes with instructions, capable of adapting, or is subject to mutation. However, it is currently impossible to say which of these qualities that unobserved life may exhibit, if any. While the definition of life is important when considering its origin and must include extraterrestrial life which may exhibit unconsidered qualities, terrestrial life is postulated to have been brought about by non-living components. Scientists have been so far able to create the building-blocks required to make a cell, but have not yet managed to create the proto-cell to bridge the gap between life and non-life.
The Study of the Origin of Life in History
Life was, at one time, believed to be spontaneously occurring. Aristotle wrote that it was “a readily observable truth” that mice came from dirty hay; aphids from the dew; and crocodiles from the bottom of a bog. Most famously, maggots were believed to generate from rotten meat– that is, until 1668 when Fransesco Redi isolated a piece of meat from the elements, and proved that without flies present to lay their eggs, maggots do not appear. Further research, especially after advances in the understanding of bacteria, spores and the transmission of disease, supported the idea that organisms do not spontaneously occur from non-living material. Life could only be generated from other life. The 17th century saw the diminishment of previous hypotheses and “Omne vivo ex ovo” (all life comes of the egg) became the dominant thought.
After chemist and microbiologist Luis Pasteur discovered – among many other things – that microbes do not grow on their own without a nutrient-rich medium, question of microbial genesis arose. If only able to generate from each other, from where did the first microbe originate? If all organisms, including humans, have evolved from simpler forms of life, from where did that life originate?
Charles Darwin, in 1871, suggested an answer. Darwin guessed that life may have begun “in a warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat and electricity, present, so that a protein compound was chemically formed ready to undergo still more complex changes". Darwin also pointed out that to recreate the moment when, let alone predict the unimaginable conditions in which the first life formed would be next to impossible in a world now full of life – to attain that ultimate sterility would be next to impossible.
Research of the 20th Century
Darwin’s “primordial soup” theory was further developed in the 20th century. Until 1924, oxygen was considered necessary component. Aleksandr Oparin, however, postulated that early earth little or no oxygen in its atmosphere, and instead consisted of methane, ammonia, hydrogen, and water vapor. It was from these that the first life had probably been borne. He observed that some molecules self-organize into droplets and layers, which would be an important step in the formation of cells.
In 1953, Stanley Miller expanded on Oparin’s research by actually making simple cellular building-blocks out of a simulated primordial soup. Miller simulated the reduced conditions of early earth, by mixing together the methane, ammonia, hydrogen, and water and sealing it in tubes and flasks. The liquid water was heated to create water vapor in the system, and lightning was simulated with electrical sparks. After one week of cycling through heating, cooling and electrifying, 12% of the carbon molecules within the closed system had turned into organic compounds. 2% of those were in the forms of amino acids, including 2 recognizable amino acids that are used to make proteins in living cells; sugars and fats were also formed, as well as the building blocks of nucleic acids.
Miller demonstrated that when exposed to an energy source such as electricity, or ultraviolet light from the sun, inorganic compounds could react to form amino acids and the building-blocks of nucleic acids.
Researcher Sidney Fox studied the formation of peptide structures out of amino acids using compounds found in early earth, and showed that peptides could be coaxed to form spherical membranes, similar to that a cell might require.
In 1969, the meteorite called the Murchison Meteorite was recovered and found to have contained over 90 different amino acids, 19 of which are known on Earth, including some of the basic amino acids produced in the Miller-Urey experiment. Since there is evidence for comets heavily bombarding young earth, it is possible that the building-blocks of life were delivered from environments different from earth’s own, making it difficult to study with certainty the conditions under which the compounds formed.
Meteorites have been shown to include many pre-organic or organic molecules. The most common meteors to be collected on Earth are carbonaceous chondrites, usually rich in water and organic compounds. The addition of these compounds could have possibly kick-started the creation of life on earth.
Many researchers have contributed to the study of the origin of terrestrial life with different hypotheses, including theories of life emerging in earth’s oceans near extremely hot volcanic vents, by ocean waves creating bubbles and sea foam on a warm shore concentrating pre-biotic material, or a creation of organic compounds brought about by richer uranium (and a more highly radioactive) content in the soil caused by a closer moon. All of these are viable hypotheses, but not easily testable.
The current scientific consensus is that terrestrial life arose from non-life, although no scientific experiment has been able to create a living cell. Geologic evidence points to the abundance of methane, ammonia, hydrogen, and water on young earth; it was most likely from these elements that living things form. Scientists like Stanley Miller were able to create amino acids and other organic molecules from these compounds, and Sidney Fox encouraged the growth of peptides from amino acids forms from inorganic materials, which spontaneously formed into a spherical membrane, a shape similar to that a cell would require. So far, the only life has come from previous-existing life; as scientists research the cell and its parts, they inch closer to being able to create a cell in the laboratory.
Perhaps scientists are close to completing this task with the current technology. Perhaps technological innovations are necessary to see it through. The first use of bioengineering spliced a gene in bacteria, inducing it to produce insulin; before that, insulin was procured from cattle and pig pancreas. If complete control is
given over the engineering of a cell, then the operation of the cell can easily be understood more
From where did life come? Most likely from a world of methane, hydrogen, water, and ammonia. The day that life will be able to create life without reproduction will be a remarkable event in history - the creation of a tiny building-block of life may bring with it possibly unprecedented consequences.
1. Erwin Shrodinger Article, “The Material Basis of Life”. http://intothecool.com/energetic.php
2. Spontaneous Generation – University of Cincinati’s Biology Website
3. Darwin, Francis, ed. 1887. The life and letters of Charles Darwin, including an autobiographical chapter. London: John Murray. Volume 3. p. 18
4. University of Arizona, Lecture on the Origin of Life. http://nitro.biosci.arizona.edu/courses/EEB105/lectures/Origins_of_Life/origins.html
5. “The Murchison Meteorite” on the Timeline of Life at PBS.Org. http://www.pbs.org/exploringspace/meteorites/murchison/index.html
6. Carbonaceous chondrites at The Encyclopedia of Astrobiology, Astronomy, and Spaceflight. http://www.daviddarling.info/encyclopedia/C/carbchon.html