RNA Hypothesis
The hypotheses of the origin of life on the planet Earth have always been numerous. Darwinian Theory explained everything but the appearance of cells as the smallest units of life. The theory of prebiotic soup seemed to fill in the gap when Miller passed the electricity through the mixture of “water, methane, hydrogen, and ammonia” and obtained the “soup” in which the primitive life forms appeared (Robinson, 2005). But this theory was defeated by the experiments that proved the atmosphere of earth to have different chemicals proportions under which the electricity would not create life. After this, the RNA hypothesis appeared like the way to explain how cells emerged, developed, and multiplied. As DNA is the cell-building basis, scholars doubted if RNA can carry some genetic material applicable for cell replication, but experiments prove that RNA can be the lacking part of the cell appearance hypothesis.
Metabolism-First Hypothesis
The metabolism-First hypothesis is the theory that opposes the RNA hypothesis. The essence of the hypothesis, formulated by Wächtershäuser in 1988, is in the assumption that the initial life forms appeared not by way of replication but through the metabolism of inorganic compounds containing “carbon dioxide, hydrogen sulfide” (Robinson, 2005). The ability of iron disulfide to catalyze simple chemical reactions has been long known to scholars and they assumed that this element might serve as an impact on the beginning of life on Earth. Given the harsh conditions on Earth of the time, the supporters of the metabolism-first hypothesis assumed the above reactions to take place “at deep-sea hydrothermal vents” (Robinson, 2005) and at higher molecules concentrations than assumed by the RNA theory, whose conditions are called by the supporters of metabolism to be impossible in reality.
Astrobiology and Panspermia Hypothesis
There are some other theories of the origin of life on Earth. One of them is the Panspermia theory formulated first in 1865 and based on the assumption held by the astrobiologists that the simplest forms of life could have been brought to Earth from space either by comet crushes or in any other way (Shwartz, 2000). The Panspermia theory argues that there are several areas in the universe, except Earth, where there are fitting conditions for life development, and the simplest organisms from those areas, including Mars and Europa, could have been brought to Earth and could have survived the terrible boiling or freezing temperatures that were observed on Earth four billion years ago. Having tested the microorganisms of the kind, scholars proved that they can stand the temperature of 10Gs for four days and remain alive and active (Shwartz, 2000).
Mineral Mica Hypothesis
The mineral mica hypothesis, formulated by Hansma in 2007, argues that life could have begun in the protected layers of the mica mineral mixtures observed at the deep sea. The layers of the mica are separated and filled with water and chemicals necessary for replicating the biomolecules and first simplest cells (University of California, 2007). Moreover, the mentioned isolation of the layers facilitates the Darwinian evolution theory and connects it with the mica hypothesis. Also, Hansma explains that her theory explains both RNA and metabolism hypothesis and makes them all possible in the layers between mineral mica formations. Accordingly, the latter theory is the most credible and comprehensive in its scope.
Works Cited
Robinson, Richard. “Jump-Starting a Cellular World: Investigating the Origin of Life, from Soup to Networks.” PLOS. 2005. PLOS Biology.
Shwartz, Mark. “New field of astrobiology has scientists pondering extraterrestrial origin of life.” News. 2000. Stanford Online Report.
University of California. “New Hypothesis For Origin of Life Proposed.” UCSB. 2007. Santa Barbara.