…a species developed that was not like the other species. In the course of doing its thing, over time, it changed the environment so much that many of the other species found it hard to survive. Eventually, it remade almost the entire planet in such a way that many, if not most, of the species that were around when it first arose were driven to extinction.
We’re talking, of course, about the first cyanobacteria.
For some untold eons prior to the evolution of these cyanobacteria, during the Archean eon, more primitive microbes lived the real old-fashioned way: anaerobically. These ancient organisms—and their “extremophile” descendants today—thrived in the absence of oxygen, relying on sulfate for their energy needs.
But roughly 2.45 billion years ago, the isotopic ratio of sulfur transformed, indicating that for the first time oxygen was becoming a significant component of Earth’s atmosphere, according to a 2000 paper in Science. At roughly the same time (and for eons thereafter), oxidized iron began to appear in ancient soils and bands of iron were deposited on the seafloor, a product of reactions with oxygen in the seawater.
“What it looks like is that oxygen was first produced somewhere around 2.7 billion to 2.8 billion years ago. It took up residence in atmosphere around 2.45 billion years ago,” says geochemist Dick Holland, a visiting scholar at the University of Pennsylvania. “It looks as if there’s a significant time interval between the appearance of oxygen-producing organisms and the actual oxygenation of the atmosphere.”
The cyanobacteria wiped out species of anaerobic bacteria – and caused climate change:
Free oxygen is toxic to obligateanaerobic organisms, and the rising concentrations may have wiped out most of the Earth’s anaerobic inhabitants at the time. Cyanobacteria were therefore responsible for one of the most significant extinction events in Earth’s history. Additionally, the free oxygen reacted with atmospheric methane, a greenhouse gas, greatly reducing its concentration and triggering the Huronian glaciation, possibly the longest snowball Earth episode in the Earth’s history.
Of course, *we* – and the whales, polar bears, great apes, tree frogs and every other oxygen-breathing creature – would not exist if it weren’t for oxygen producing bacteria, and the green multi-cellular plants that followed them. Tough break for all but a few anaerobic bacteria, though.
So, Question: if cyanobacteria are natural and good, yet they caused both a mass extinction and climate change that dwarf in severity anything people have done or are likely ever to do – why, exactly, do we say that people are bad when we do things that cause extinctions and (maybe) change the climate? It can’t be because mass extinctions and climate change are bad in themselves – they are as natural as nature can be.
If you answer: because human beings are different, then answer: how are we different? How are we, and everything we do, not just as natural as what cyanobacteria did? If we are to be held to a higher standard of behavior than plants and animals – why? Where did that standard come from? What compels me – or should compel me – to adhere to that standard?
My answer: I like a beautiful planet full of interesting and beautiful plants and animals; I like vistas of rampaging seas, purple mountains and amber waves of grain. I love my children, and want them and everybody else’s children to be able to live on a beautiful planet as well. Therefore, I will try not to needlessly destroy natural beauty. But please note: it is completely unnatural, in the sense that what plants and animals do by nature, to want this. No plant or animal gives a second, or even a first, thought to ‘saving the planet’ or any other species or any particular environment. Only Man worries about such things.
If the species Man is just another part of the natural world, nothing we do can be judged as unnatural, evil or destructive; if not, we must be something more than natural.