Bryson, Bill - On the Reasons for the Extinctions
Type of Spiritual Experience
A description of the experience
There appear to be three reasons why extinctions occur:
- Some events remove species that have reached the biological endpoint of their tree of life – their evolutionary cycle. In other words extinction events selectively target species that have reached their full potential from a design and functionality increase point of view
Bill Bryson - … there is one extremely pertinent quality about life in earth: it goes extinct. Quite regularly … species crumple and die remarkably routinely. And the more complex they get the more quickly they appear to go extinct.
- Some events target species that have achieved their objective as an agent of change. There are some species that are not there to increase functionality, but have been introduced to help as agents of change environmentally. In effect they are there to provide the conditions necessary for the next stage. Once they have achieved that change they effectively die out.
Bill Bryson - One reason life took so long to grow complex was that the world had to wait until the simpler organisms [cyanobacteria, stromalites etc] had oxygenated the atmosphere sufficiently. It took about 2 billion years, roughly 40% of Earth's history for oxygen levels to reach more or less modern levels of concentration in the atmosphere ….. once the stage was set and apparently, quite suddenly, an entirely new type of cell arose – one containing a nucleus and other little bodies called organelles
- Some events target life forms that would threaten the evolution of the ones planned.
Bill Bryson … extinction is always bad news for the victims, of course, but it appears to be a good thing for a dynamic planet. Crises in the Earth's history are invariably associated with dramatic leaps afterwards. The fall of the Ediacaran fauna was followed by the creative outburst of the Cambrian period. The Ordovician extinction of 440 million years ago cleared the oceans of a lot of immobile filter feeders and somehow created conditions that favoured darting fish and giant aquatic reptiles. These in turn were in an ideal position to send colonists onto dry land when another shakeout in the late Devonian gave life another sound shaking. If most of these events hadn't happened just as they did, just when they did, we almost certainly would not be here now.