The Question of Primacy

When we ask “what came first, plants or fire?” the image of a flickering flame seems elementary, yet the scientific answer flips intuition: vegetation predates combustion by tens of millions of years.

Oxygen’s Role in Combustion

Fire cannot simply ignite in a vacuum. It requires a minimum concentration of molecular oxygen—approximately 13 % in the surrounding air. Below this threshold the oxidation reaction proceeds too sluggishly, and any heat generated dissipates faster than it can be replenished, extinguishing the flame.

An Oxygen‑Free Early Atmosphere

During the first two billion years of Earth’s history, the atmosphere was virtually devoid of free oxygen. Geochemical clues from ancient rock strata—such as the absence of rusted iron, peculiar chromium and molybdenum compounds, and the presence of sulfur species that only form under ultraviolet bombardment—confirm this oxygen‑poor environment. Without oxygen there was also no protective ozone layer, allowing relentless UV radiation to bathe the surface.

Rise of Cyanobacteria and Plant Life

The turning point arrived when cyanobacteria evolved the ability to perform oxygenic photosynthesis, gradually enriching the air with O₂. This biogenic oxygen surge transformed planetary chemistry and set the stage for terrestrial colonisation. Land plants emerged roughly 475 million years ago, taking advantage of the newly oxygenated atmosphere.

First Evidence of Fire

Archeological and paleontological records place the earliest unequivocal signs of fire at about 425 million years ago—approximately fifty million years after the first plants rooted on land. Charcoal deposits, soot layers, and burned plant fossils provide the hard data that scientists use to date this phenomenon.

In summary, the Earth’s timeline shows a clear sequence: an oxygen‑starved world, the advent of photosynthetic microbes, the appearance of terrestrial flora, and finally the ignition of fire. The flame that later shaped ecosystems, human culture, and technology was, paradoxically, a relatively latecomer.

Source: https://scientias.nl/wat-was-er-eerder-de-plant-of-het-vuur/