Not only that but the "primitive atmosphere" of methane and ammonia necessary for that first cell to emerge is now irrelevant.
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Not only that but the "primitive atmosphere" of methane and ammonia necessary for that first cell to emerge is now irrelevant.
Quote & full article:
Early cells may have used membrane pigments to protect themselves from the then intensive UV. The excitation of these pigments could become coupled to proton pumping and the resultant gradient used to drive ATP synthesis. Bacteriorhodopsin does this in some modern bacteria. Modern proteobacteria split hydrogen sulphide to provide electrons for this process, and this probably pre-dates oxygenic photosynthesis. However, water is obviously very abundant so there would have selection pressure to split water and so release oxygen. Initially, oxygen released by photosynthesis was absorbed by iron (II), then abundant in the sea, thus oxidising it to insoluble iron (III) oxide (ie, rust!). Red 'banded iron deposits'of iron (III) oxide are marked in marine sediments of ca.2500 mya. Once most/all iron (II) had been oxidised to iron (III), then oxygen appeared in, and began to increase in, the atmosphere, gradually building up from zero ca.2000 mya to approximately present levels ca. 500 mya. This was the "oxygen revolution". Oxygen is corrosive, so prokaryotic life then either became extinct, or survived in anaerobic (oxygen free) environments (and do so to this day), or evolved antioxidant protective mechanisms. The latter could begin to use oxygen to pull electrons from organic molecules, leading to aerobic respiration. The respiratory electron transport chain probably evolved from established photosynthetic electron transport, and the citric acid cycle probably evolved using steps from several biosynthetic pathways (it still has key links to biosynthesis today).
http://www.staffs.ac.uk/schools/sciences/biology/Handbooks/evolearly.htm
Okay, so UV light is not only not a problem for the formation of life, it was probably essential. I found another source which I can't pin down at the moment, which stated that in an addition to the poisonous presence of oxygen causing a major round of extinction, the development of the ozone layer also forced the extinction of those UV-dependent life forms.
Next will come lots of naysaying about the use of the words "may have" and "probably" in the above quote