If you feel like you spend your whole life waiting around because of delays, you might want to count your blessings that you weren’t around on Earth back in its middle ages.
That’s because scientists have now revealed that the evolution of our planet was halted for a (rather lengthy) two billion years because oxygen in our atmosphere was trapped at chronically low levels.
Around 2.4 billion years ago, the ‘great oxidation event’ was responsible for first bringing oxygen into our atmosphere. But scientists were baffled as to why, despite photosynthesis occurring, the oxygen was set at about 10% of the levels we have today.
Now Professor Tim Lenton and Dr Stuart Daines believe that plate tectonics were the missing part of the puzzle.
The shifting of the earth’s crust helped to force a build-up of organic material in sedimentary rocks to the surface.
After that the material was able to react with oxygen in the atmosphere for the first time and establish a regulatory mechanism where oxygen was consumed at the same rate at which it is produced.
It was only then that the rise of plants could occur, doubling the levels of photosynthesis and overriding the control on oxygen, rising to the levels needed for humans.
Professor Lenton said: “This time in Earth’s history was a bit of a catch-22 situation. It wasn’t possible to evolve complex life forms because there was not enough oxygen in the atmosphere, and there wasn’t enough oxygen because complex plants hadn’t evolved.”
Who knows, perhaps humans could have appeared sooner than 200,000 years ago if earth hadn’t stalled for quite so long.