Oxygen is a gas we generally take for granted here on Earth thanks to the abundant flora that keeps its levels in our atmosphere nice and high. Not only it is vital for our bodies to power themselves, but it’s essential for quite a bit of our technology. Metallic alloys and plastics on which we rely to build everything from buildings to spacecraft, require fire to smelt, mix, and mold. Even something as basic as pottery and bricks still require an oven with a steady flame, and cooking food to kill bacteria and parasites, would be impossible without a nice, roaring fire. And if you want fire and heat without having to deal with a violent volcano belching noxious fumes, you need to have oxygen. I learned this as a kid in science class, giving it little thought until recently, when my girlfriend asked me if aliens living on a planet which didn’t have oxygen could ever develop a civilization as we know it since they’d never be able to start a fire to cook their food, much less build advanced technology.
Now, I really didn’t know how to answer her question, but after giving it some thought, I think she might have a very interesting point. After stone tools, the first major leap forward for humans was fire. With food that was far safer to eat and much easier to chew and digest, we could get more from our nutrition. On cold nights, a good fire would warm our caves and huts. And fire allowed for the next leap forward, the invention of metal tools and the ability to create lighter and more durable weapons to defend our farms and hunting grounds. And you may even say that fire was one of the technological catalysts for the emergence of human civilization as we know it today. For fire, though, we needed to have oxygen in our atmosphere. So what would’ve happened if the Earth produced macro life that didn’t need oxygen and the reactive gas was present only in very trace amounts? Say goodbye to caves that could be warmed on demand, creating custom tools from metal, or even making basic pottery wherever you want. And even if you could just walk up to a superheated volcanic vent, you would have a lot of trouble making tools that wouldn’t burn up or melt from the magma’s radiant heat.
Even if you’re extremely creative and manage to tap into a geothermal source, you can forget about controlling the temperature to create exactly what you need because it really isn’t as simple as moving what you need to heat to the right distance from the magma. All sorts of environmental factors would affect the heat that’s being put out of the vent and the exposure to noxious gases would be a major problem for any macro life. Basically, you really need to get heat on demand if you want to build cities close to easily traversable terrain, rivers, and seas, and if you want to make materials that require a very precise recipe, materials you can use in everything that’s needed to build computers, radios, TVs, lenses, and mirrors, you’re out of luck. Does that mean that we have to look for a world with oxygen in its atmosphere if we ever want to find alien cities, and not because we want to find high levels of atmospheric oxygen as a requirement for life, but because we’re looking for species that can discover fire? Maybe there’s a chemist in the house who could set us straight and let us know if there may be another way of creating a controllable heat source in an atmosphere without oxygen? And what do you think? Can one have a technological society without having to discover how to handle fire first?