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A brief history of Organic Geochemistry
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A relatively recent science
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Origin of Coal
Humans use coal and petroleum since thousands of years but the origin of these fossil fuels was only elucidated over the last two centuries. Coal was recognized early as being derived from plants as it often contains unambiguous plant fossils. The continuum of plant to peat to coal was quickly understood. In 1896, Edward A. Martin wrote in a booklet entitled 'The story of a piece of coal' that "there are few now who do not know what was the origin of the coal which they they use so freely, ..." meaning that the origin of coal was known to the general public by the end of the 19th century.
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Illustration from the book "Story of piece of coal" by Edward E. Martin (1896) showing fossil plants found in coals and associated sediments. |
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Origin of Petroleum
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Treibs (1936) identified porphyrins in oil and related these compounds to chlorophyll
From biomolecules to geomolecules |
In contrast, the origin of petroleum was fiercely debated well within the 20th century. In 1924, a United States Geological Survey report on natural hydrocarbons indicates: "No subject in geochemistry has been more discussed than the origin of oil". Some still advocated a cosmic origin for petroleum (delivered to Earth during the consolidation of the planet and since emitted from the Earth's interior). Others favored a synthesis of hydrocarbon from carbon dioxide in the interior of the Earth and subsequent polymerization. Most already favored an organic origin, with oil deriving from marine organisms. Microscopic algal remains had already been observed in petroliferous rock formations.
It is broadly considered that the proof for a biological origin of oil was provided in the 1930's with the work of the German chemist Alfred Treibs. In 1936, Treibs identified porphyrins in bituminous sediments and related these porphyrins to their precursor in living plants, chlorophyll. For the first time, a molecule derived from the geosphere (geomolecule) was related to a precursor in the biosphere (biomolecule). This evidence reinforced the paradigm of the biological origin of petroleum. For many, Treibs' seminal manuscript represents the birth of organic geochemistry. 
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Further readings
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A more detailed history of organic geochemistry can be found in the following publications:
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