Palaeontologists have a fine time of it. They fossick around in obscure parts of the world where there are few people and take a hammer to rocks.
They have done this for generations, found lots of fossils, and come up with some interesting conclusions.
Here are five of them.
- 444 million years ago 86% of species were lost.
- 375 million years ago 75% of species were lost
- 251 million years ago 96% of species were lost
- 200 million years ago 80% of species were lost
- 66 million years ago 76% of species were lost.
These are, of course, the five mass extinction events in the fossil record. The last one being the most famous when all the dinosaurs copped it.
Here is another pattern they found
Over time diversity has increased despite these mass extinctions and several smaller ones in between them.
There are more species alive today than at any other time in evolutionary history, despite the obvious fact that humans are kicking the sixth mass extinction into existence.
This is the history of life on earth. It is dynamic with huge shifts in diversity but with an underlying driver powerful enough to increase diversity over time.
If you believe this evidence then a few core concepts become clear:
- Extinction happens.
- Large extinction events happen often enough to make another one inevitable.
- After extinction events, diversity recovers
- And for at least 150 million years the trend is for diversity to increase rapidly, noting that the non-avian dinosaurs were lost during this time.
Diversity happens because there is time enough for mutation and natural selection to hone any number of specialisms. When organisms specialise they are successful in a relatively narrow set of conditions. A proportion of species become vulnerable to change in those conditions.
Enter human beings. Modestly specialised initially but with a distinct advantage. They had the brains and communication to adapt to a wide range of conditions, especially when they tamed fire and then much later discovered fossil fuels.
Once in control of energy humans have appropriated over half the global biomass production, removed vegetation, getting rid of wildlife and altered the composition of the atmosphere. More than enough change for mass extinction.
Humans affected the change but change would have happened at some point. Tectonic plates moving to cut off ocean gyres, volcanic eruptions, another meteorite strike, it would happen soon enough, maybe 50 million years hence.
Is the reality of extinction too painful?
Perhaps it is. Perhaps we are just too much in the present day to accept timeframes beyond ourselves. Certainly, there will be huge consequences of extinction for our production systems, the ecosystem services we rely on, and the very liveability of the planet for our species.
We’ll need a lot of adaptation to survive.
What we might also remember as we plan for change and seek to retain what we can of the diversity of life, that extinction is real and inevitable. It is as much a part of the process of evolution as the creation of new types.
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