GHung wrote:Time for life (fairly advanced life, in the case of the Greenland fossils) to evolve from a primordial soup? Or evidence that the planet was being bombarded all along with seeds of life, until conditions were suitable for life to take hold?
There are many problems with the old primordial soup theory and panspermia is pretty fringe. Perhaps there was a much simpler, more direct way for life to begin. Here is one of the best lectures I have ever seen:
Inevitable life?https://www.youtube.com/watch?v=ElMqwgkXguwMany researchers have supposed that the emergence of life hinged on a sequence of improbable events, at the same time as they have taken for granted the ability of life on earth to persist indefinitely and to "freeze in" the consequences of early accidents. Smith argues that there is ample evidence for a different interpretation: the emergence of life was an inevitable outcome of geochemistry on the early earth, and the same forces responsible for emergence have continued to support the persistence of life ever since.
I think this is the most compelling explanation for the origin of life. It turns out that life is an inevitable biochemical process. Life was pushed into existence because it is the best way to release the energy trapped in hydrogen and carbon dioxide that builds up because of geothermal processes. Hydrogen can give electrons to carbon and oxygen to form methane and water. That is the most energy energy available from the system. Life had to begin to release this constantly building trapped energy, providing a downhill run to lower energy molecules. There is no other chemical process that can do it. It has to run through the molecules of life (fatty acids, amino acids, sugars, cofactors, and nucleic acids). Krebs cycle (in reverse, actually).
The emergence of life is a chemical breakdown. The metabolic processes of life began before life did. Life exists and persists to enable metabolism. The biosphere arises from the geosphere. Life began at the bottom of the oceans around hydrothermal vents. Some of the oldest forms of life ever discovered are autotrophs that live around hydrothermal vents.