Origin of Life: Miller's Experiment

Study Notes

In 1953, Miller conducted experiments on molecular evolution, exposing a mixture of H2, CH4, NH3, and H2O to high electric discharge, resulting in the formation of advanced molecules, including CO, CO2, N2, and amino acids like glycine and valine.
The experiment led to the formation of a liquid condensate phase, including a variety of amino acids and other organic molecules.
During this period, certain compounds that favored molecular evolution survived, while those that disfavored it were destroyed by predator molecules like hydrated electrons and poly anions.
The culmination of chemical evolution was the polymerization of monomers, resulting in the formation of biopolymers like proteins, polysaccharides, lipids, and polynucleotides.
Certain polymers like histones and protamines, which are positively charged, enclosed polynucleotides, protecting them from predator molecules.

The hypothesis was confirmed by the tracer carbon technique and chromatographic identification of the products (Arnon, 1960).

The evolution of the chlorophyll molecule was a landmark in the origin of photosynthetic life, as it is capable of emitting electrons when excited by radiant energy.
The evolution of photosynthetic life could change the reducing environment to an oxidizing one due to the release of oxygen.

At the time of the origin of animals, the atmosphere contained N2, CO2, and O2 gases, while the land mass contained soil rich in soluble nitrates, sulfates, phosphates, and organic materials.

Jean Baptiste de Lamarck (1744-1829) proposed the theory of inheritance of acquired characters, also known as the "Theory of Use or Disuse of Organs".
According to Lamarck's theory, as giraffes stretched to reach high branches, their necks lengthened, and this was passed on to their offspring.
The basic ideas of Lamarckism are:
- Complex plants and animals are produced from simpler ones over time under the influence of nature.
- Living organisms have a tendency to continuously increase in size.
- There is a change in the needs of an animal due to changes in the surrounding environment, leading to the formation of new organs.
- If an organ is used continuously, it becomes more powerful, and if it is not used for a long time, it weakens and eventually disappears.
- The characters acquired during the lifetime of individuals are transmitted to the next generation.

Lamarck based his idea of use and disuse on the evidence of vestigial organs and rudimentary organs.
The idea is true, but it cannot be treated as a basis of evolution.
Weismann (1890) provided experimental proof against the theory of inheritance of acquired characters, showing that changes in germ cells are inherited, not somatic changes.

A few scientists, including Herbert Spencer, Haeckel, and Gadow, have supported Lamarckism in a modified form, known as Neo-Lamarckism.

Charles Darwin joined a sea voyage on the HMS Beagle, collecting flora and fauna from many continents and islands.
Darwin noted unexpected patterns among fossils and living organisms, leading to the development of his theory of how species might change over time.
Fossils resembled but were not identical to living organisms in the same area where they were found.
Finch species on each of the Galapagos Islands differed from each other in small but significant ways.