Nearly 2 million years ago, our ancestors, Homo erectus, began using fire. The use of fire paved the way for our evolution. But how important was fire to the development of civilizations? A recent study reveals an interesting connection between atmospheric oxygen and the possibility of fire-powered civilizations on other planets. This leads us to the question: is atmospheric oxygen (and fire) a necessity for the development of technological civilizations?
Homo Ignus – Possessor of Fire
Nearly 2 million years ago, our upright ancestors Homo erectus began to harness the power of fire. The shift from the casual use of natural fires to the mastery of fire creation laid the foundation for human evolution. We became beings defined by fire, relying on it for cooking, heating, and lighting. But this begs the question: is it possible for civilization to evolve without fire?
The existence of fire is linked to the presence of oxygen in the atmosphere. An open fire requires an atmosphere containing at least 18% oxygen; a reliable fire may require 20%. Our current atmosphere consists of 21% oxygen, but it has only remained above 18% for the last 200 million years. Thus, fire has been unavailable for most of Earth’s history. This highlights that planets that support fire may be rare in the universe, potentially limiting the emergence of civilizations elsewhere.
A recent study sheds light on the narrow throat of the
A recent study published on the Arxiv pre-publication server explores the conditions required for an oxygen-rich atmosphere and shows that they are extremely specific. There are two main ways to create free oxygen: biologically by photosynthesis and abiotically by splitting water vapor into hydrogen and oxygen by ultraviolet radiation.
The study emphasizes that the predominant mechanism depends on the size and temperature of the planet. On Earth, free oxygen requires living organisms. A planet that is too small does not have enough atmosphere for life, and if it is too large, its atmosphere, composed mainly of hydrogen and helium, cannot produce enough oxygen to pass the 18% threshold. Consequently, the inhabitants of a super-Earth with temperatures similar to Earth’s may not have access to open fire.
The case for hotter planets
For warmer planets, the abiotic process becomes dominant, but only if the planet is larger than Earth. Smaller hotter planets, such as Venus, do not create a thick enough layer of water vapor to generate significant amounts of oxygen. If we find super-Earths with oxygen-rich atmospheres, it probably arose from abiotic processes, potentially allowing life forms to use that oxygen even for fire-based civilizations.
The article does not delve into every detail of atmospheric oxygen, but seeks to outline the limitations to the emergence of fire on potentially habitable worlds. As we explore the cosmos in search of signs of life, we will have to distinguish between worlds that support life and those that harbor civilizations.
