Fire destructs. Not always though. Ask the scientists who suggested that invention of cooking was a watershed moment in human evolution. They attribute increase in human brain size to fire – the use of fire. Good on those ancestors then who first chose to play with fire. We wouldn’t be us without them.
Devastating forces are all around us. The key lies in control. We have learned to control fire and make use of it. This risk taking has brought dividends to us. Did life come out of similar such risk taking in the first place?
What do we really mean by fire? Two substances – oxygen and fuel – cause fire when they come together in presence of heat. When the heat reaches a threshold, it triggers the first oxidation reaction. The fuel breaks down into simpler chemicals. The reaction is exothermic meaning it gives out energy. The energy in the form of heat triggers the next fuel molecule to ‘burn’ and a chain reaction begins. It ends with exhaustion of either oxygen or the fuel or when some external factor draws energy out of the system. The ‘light’ part of the energy makes us see the fire as flames. The end products of the chain reaction are water and carbon dioxide that go up in the atmosphere.
Do the two substances remind us of something close to our hearts? Our cells run a similar process with sugar as fuel and oxygen. We consume sugar as food and breathe in oxygen as air. The end products are water and carbon dioxide and a whole heap of energy in the form of ATP molecules. You got it right. The process is cellular respiration.
Alright, so you’ve noticed my clever omission of the role of heat in the above cellular process. The energy part is the real trick here that makes ‘life’ so interesting. Here is how.
We take in the sugar and the oxygen. Both are produced by the plants. In that sense we animals are parasites though science does not label us as such. The plant, via another outstanding life process photosynthesis, binds the light energy into sugar molecules. If we see the life in totality, the energy consumption part of the process happens in the plants. The strong chemical bonds of sugar molecules store the energy. During respiration, that stored bond energy is released which drives us to ‘burn’ more sugars.
The fire at the cell level is that photon which life has learned to control and capture and make use of to produce food for its processes. Life’s evolution, if not the origin, is thus fuelled by fire in the form of sunlight – the only regular external input into the earth system. Some primitive form of life – perhaps some microbe – first dared to play with that fire and here we are today, alive and kicking.