From New Scientist:
For the first half of Earth’s existence, there was no oxygen to be had. The air wasn’t breathable and life in the oceans was little more than primitive sludge. Even in this hostile world, though, small “oases” of oxygen-rich water persisted, fuelled by bacteria. Now it seems we have found the first hard evidence of one of these oxygen oases, preserved in ancient rocks.
If a person were to step out into this ancient world, they would die of asphyxiation within minutes. It wasn’t until around 2.4 billion years ago that oxygen flooded the oceans and gave rise to the air and seas we recognise.
“But many researchers have suspected that the first biological production of oxygen began long before that,” says Timothy Lyons of the University of California, Riverside. Rocks from 4 to 2.5 billion years ago often contain bands of iron-rich minerals. These formed when bacteria started pumping out oxygen, which reacted with dissolved iron in the ocean to form particles of rock that sank to the bottom. More.
The researchers investigated Steep Rock Lake in Ontario, Canada. They found a mixture of iron minerals, and stromatolites (ancient microbes) in the limestone, preserved from 2.8 billion years ago. Oxygen reacts with iron to produce iron minerals. The researchers believe that “the best explanation for the presence of the iron mineral is that bacteria pumped out oxygen, which reacted with all the iron in the water.” The limestone (calcium carbonate) can only form in the absence of iron.
Because oxygen is chemically reactive, when it first built up it was a deadly pollutant. Bacteria living in the oases would have been forced to evolve oxygen-defence mechanisms, or die. So the oases would have pushed early life to adapt to oxygen, before the gas went global.
Accounts like these, while intriguing, give one pause for thought. Think about the huge assumption here. Science writer Michael Marshall, who wrote the piece, simply assumes that bacteria “would have been forced” to evolve, as opposed to just going extinct. But why? Is there a natural law that mandates evolution in such cases? How? Why? Life forms do “want to” stay alive (stay organized at a high level of information?) But what drives them? How does it work, especially in life forms with no brain? That is, they can’t be forced to evolve if nothing is forcing them to. One can argue for law or design, using that language, but not chance. Thoughts? See also: Does nature just “naturally” produce life? Can all the numbers for life’s origin just happen to fall into place? and The Science Fictions series at your fingertips (origin of life) Follow UD News at Twitter! Here is a short clip on modern stromatolite colonies.