For most of Earth’s history, fire could not be made due to lack of oxygen.

The first signs of charcoal in the fossil record, an indicator of forest fires, do not appear until 420 million years ago.

This means that there was no fire on Earth for 90 percent of its entire history. The reason? That 420 million years ago, oxygen levels exceeded 13 percent for the first time.

Prior to those dates, atmospheric oxygen levels on Earth were so low that combustion simply could not be sustained, even if there were volcanic eruptions. As Lewis Dartnell explains in his book Origins:

Thus, the increase in this not only allowed more complex life to evolve on Earth, but also gave humanity fire as a tool. We first use it to get rid of the night chill and to keep predators at bay, to cook food and to clear the land.

The most complex multicellular life depends on oxygen to survive, as well as an ozone layer to protect the planet’s surface from ultraviolet radiation. Thus, while many organisms were poisoned by reactive oxygen or relegated to anoxic havens, complex life came pouring in like fire did.

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