The earliest oxygen-breathing bacteria (Evolution)

by David Turell , Sunday, October 23, 2011, 20:08 (4588 days ago) @ dhw

Konhauser, however, says the water-based bacteria constituted the “first primitive oxygen-dependent life form”, and “our ancestors started off in a pool of highly acidic water”. The water didn’t become highly acidic until land-based bacteria that were ALREADY oxygen-dependent had broken down the pyrite, in which case I still don't understand why they weren’t the ancestors that started us off. Apologies if I’m being obtuse, and I promise not to badger you with this again!

If the atmosphere had no oxygen or a tiny amount we must assume that organisms could use only what was present and that was not oxygen. These organisms were not oxygen dependent. When there was a substantial increase in oxygen then some organisms could mutate and use oxygen. Oxygen is an extremely caustic and dangerous substance. Think of rusting iron tools; we consume anti-oxidents to protect our bodies. Our bodies use oxygen with many protections. Those pyrite organisms had to carefully adapt to oxygen. At the same time those pyrite eaters acidified the water. That is what they do today. In brief, image that several factors are changing at once, and bit by bit as oxygen became more and more available from oxygen producing organisms, more and more organisms learned to use oxygen. That is the best explanation I can give. Remember, first no oxygen, then a gradual increase. The environment we have today developed bit by bit.