According to Greek legend, the titan Prometheus so angered the gods, he was punished by being chained to a rock and having his liver pecked out by an eagle for all eternity. What crime was deserving of such a punishment? Prometheus stole fire from Mount Olympus and gave it to mankind.
The part fire has played in the development of the human species has a long history in our culture. Just as Ancient Greece had its Promethean legend, so too does the relationship between fire and human development play a role in modern stories. In Alien 3, for example, Ripley asks the inmates of a prison colony if they have the capacity to make fire, implying that, should they lack this capacity, they are living in a pre-civilised condition.
It’s not too difficult to see why fire so fascinates us. It’s beautiful but deadly. It protects us with light and warmth but it is also destructive. In this essay, I want to share some things I have learned about fire and the ways it has contributed to our development.
According to the website Moral Science, “the Prometheus story is a great metaphor of the struggle between science and religion”. We might suppose that ‘fire’ is really meant to represent technology. In thinking about how fire first influenced the development of the human race, one might think in terms of its role in the production of metals. A species that has the capacity to make fire has the capacity to make bronze, and iron; to make tools and weapons like scythes and swords. 
However, the capacity to make fire rewarded us with one very important feature of humans long before we discovered how to work with metals like bronze and iron. Without fire, the human species would never have developed such large brains. Just like anything doing work, brains need energy. In fact, the human brain needs more energy than any other organ, accounting for up to 20% of the body’s total haul. We have to get that energy from somewhere, and it comes from our food.
One reason why humans are such brainy animals is because they have meat in their diets. Carnivores’ prey has a habit of running away and adopting other strategies to avoid becoming a meal, and that encourages the evolution of cunning, strategy and second-guessing on the hunters’ part. Also, the best building material for meat is meat. It is a complete protein package, containing all 20 amino acids and energy-rich fat. Herbivores eat plants, which take far less skill to subdue, and is far less able to feed hungry brain tissue. So, for these reasons, carnivores have larger brains compared to herbivores.
But that does not quite explain how come humans have such large brains. Pre-tech primates would find it impossible to supply a brain as large as ours with sufficient calories. Somehow, there has to be a way to extract more energy out of the food available. Most primates have guts that weigh more than four times as much as their brains, but humans are an exception because the human brain weighs more than the human intestine. How were we able to pull this trick off?
Well, in a sense, our digestive system does not just reside within our bodies. We cook our food, and that makes it more digestible, meaning we can get away with having a smaller gut. Also, cooking food causes starch to gelatinize and proteins to denature, thereby releasing far more calories compared to uncooked food. It was cooking our food that enabled us to afford brains larger than our guts.
But that was not all fire and the invention of cooking did for us, it also freed up more time.
Most animals spend a great deal of their time eating their meals. Chimps spend six or more hours a day masticating their food. For chimps, food takes no time to prepare- as soon as you have caught it or gathered it, you are ready to eat- but actually eating it takes time. For humans, the situation is reversed. Cooked food takes time to prepare but only minutes to eat. Fire is kind of like cooked food in that both are much easier to share than to make. Thomas Jefferson once said, “he who lights his taper at mine, receives light without darkening me” (a nice analogy for non-zero sum exchanges). While it takes skill and effort to start a fire using stone-age technology, it takes negligible skill to share fire. Just hold some sticks in the flames until they catch alight, and use the lighted sticks to catch other combustible material alight. If sharing is easy to do and confers benefit (such as creating non-zero sum exchanges like credit and debt in the form of favours owed and paid back) it is likely to spread. Because cooked food can be eaten so quickly, this means that somebody else can eat as well as the person who prepares a meal.
But it wasn’t just simple sharing, because the sexes tend to favour different kinds of food. It is well known that there is division of labour in hunter-gatherer tribes. According to the stereotype, men hunt and women gather. Some might suppose this is because men are free to hunt whereas women are left holding the baby. But even in societies where women don’t face a hard choice between child care and hunting, they will still seek different kinds of food from their menfolk.
In nutritional terms, women tend to collect dependable carbohydrates, whereas men are on the hunt for precious protein. Combine cooked food that is easier to share than to prepare yourself, and sexes tending toward seeking different kinds of food, and you get the beginnings of bartering, of credit and debt. The first instances of economic exchange were probably between the sexes. As Matt Ridley wrote, “there is a neat economic explanation for the sexual division in hunter-gatherers..combine the two- predictable calories from women and occasional protein from men- and you get the best of both worlds…Everybody gains, gains from trade”.
As is well known, hunter-gatherer tribes eventually gave way to agriculture. Again, fire played a role in bringing this about. Today, environmental types bewail the practice of ‘slash and burn’ whereby forests are set alight in order to clear land to grow crops on. One reason why farming rapidly spreads once started is because crops become less easy to grow as time goes by, and this encourages people lacking technology to seek out more virgin land. When a forest is burned down, you are left with soft, friable soil covered with fertilizing ash. It does not take much beyond poking a digging stick into this soil, planting seeds, and waiting for the crop to grow. After a few years, however, sunlight made available by removing the forest canopy will have caused weeds to grow, and the soil will be compacted and in need of hoeing. Eventually, tough grassroots will need to be broken up and buried in order to provide a decent seedbed, and for that you need a plough pulled by an ox or horse. But these animals require food as well, which means some land must be set aside for pasture.
For these reasons, the first farmers were more willing to adopt a policy of ‘slash, burn, plant, move, repeat’. In other words, burn down forests in order to clear land for the planting of crops, and then move on as the land becomes too difficult to work with. It remains popular with many tribal people in forests to this day. Some have suggested that, as slash and burn farming expanded in Neolithic Europe, and more people turned to a form of farming that produces nine times more carbon per head compared to today’s farming, the carbon dioxide released by those fires might have helped warm the climate.
As the human race has grown, we have faced the constant challenge of providing sufficient energy for our needs. In 1798, Thomas Malthus wrote his Essay On Population, in which he claimed food supply could not keep pace with population growth because of the finite productivity of land, and much technological ingenuity has been devoted to averting his bleak prophecy of a population crash brought about by starvation.
One of the biggest contributors in averting this disaster was the invention of the internal combustion engine. Recall that working animals need feeding, and that requires land set aside for pasture. At its peak in 1915, America’s horse population was 21 million animals and they required about one-third of all agricultural land in order to be fed. Moreover, three million acres of agricultural land went unused because it lay over 80 miles away from any railway, and a five-day trip by horse wagon cost thirty percent more than the value of grain. The invention of the internal combustion engine meant far less reliance on animals to pull ploughs and stuff, thus opening up previously inaccessible tracts of land.
I would imagine that, when considering uses for fossil fuel, most people would think of the petrol or diesel that is used to run vehicles. But, in fact, as far as agricultural energy consumption is concerned, 31% is spent on the manufacture of inorganic fertilizer, compared to 19% for the operation of field machinery and 16% for transportation. During the 19th century it did seem at times that we would run out of fertilizer and bring about the Malthusian crash. We exhausted the best deposits of guano (rich in nitrogen) and so miners turned to saltpetre deposits (which was actually ancient guano). But, by the beginnings of the 20th century, stockpiles of fertilizer were growing dangerously low. Two years before the turn of the century, the British Chemist Sir William Crookes argued that we would face catastrophe unless a way was found to chemically fix nitrogen from the air.
15 years later, Fritz Haber and Carl Bosch invented a way of making large quantities of inorganic fertilizer from steam, methane and air. According to the essay ‘Eating Fossil Fuels’, “between 1950 and 1984…world grain production increased by 250%…The energy for the Green Revolution was provided by fossil fuels in the form of fertilizer (natural gas) pesticides (oil) and hydrocarbon-fuelled irrigation.
In one way or another, we have relied on solar energy for our capacity to do work. At the base of every food chain we find organisms that use photosynthesis in order to obtain energy from sunlight and so, by consuming plant matter or consuming animals that feed on plant matter, we ultimately rely on the Sun to provide our energy. And fossil fuels are stored solar energy, so reliance on these is also, ultimately, dependence on the Sun.
Fossil fuels are in finite supply and are non-renewable, at least on timescales relevant to humans in their current mortal condition. They do have one great advantage, though, in that by the time a species has developed to the point where it can exploit coal, oil and gas as an energy source, vast reserves of fossil fuels have built up. Timber, cropland, pasture, peat and water all self-replenish, but too slowly to avoid being used up by a swelling population. Prior to the adoption of fossil fuels, every economic boom ended in a bust because renewable energy resources ran out. If you think of all the resources that have actually run out, all of them are renewable (I am talking about species extinction). 
But coal never ran out. On the contrary, it became cheaper and more abundant as time went by. By 1870, burning coal in Britain was generating as many calories as would have been expended by 850 million labourers or, to put it another way, was providing fuel equivalent to the output of 15 million extra acres of forest to burn. 
The reason why fossil fuels have become more, rather than less, abundant as time has gone by, is because the human race is a technological species. This means that resources for us are not a fixed quantity but rather dynamic variables that change as our knowledge and technical capability change. All forecasts of doom (and there have been many, and they continue to be issued to this day) take current practices and extrapolate them out into the future. But we do not carry on as we always have; we invent new practices, adopt new technologies, accumulate and edit knowledge and in so doing unlock resources that were hitherto inaccessible while also making other resources less relevant to our needs, or no longer relevant at all. Who needs whale oil to provide them with light these days? 
For much of human history, we could extract far more energy from fossil fuels compared to any renewables we could practically exploit, and that meant that, for all its bad reputation as a source of pollution, we actually did far less environmental harm using fossil fuels than would have been afflicted had we tried to support such population growth and rise in affluence with renewables. Non-renewables, in other words, were, for most of human history, the greenest source of energy available that could support a population that would ultimately number in the billions, with expectations of liberating their own from slavery and providing decent standards of living. 
But then, as I said before, resources change as scitech changes. If solar panels could be mass produced at $200 per square metre and with an efficiency of 12%, that would generate the equivalent of a barrel of oil for $30. It would then, of course, make greater economic sense to rely on solar power rather than spend $40+ dollars mining a barrel of oil. Also, we should not forget that, for all our ingenuity in finding more fossil fuel to extract, it is in finite supply and so peak energy must eventually result unless we can make fossil fuels irrelevant as an energy source by exploiting vast and renewable energy reserves that had to go untapped by our ancestors because of their lack of technological capability. 
From using fire to cook and providing ourselves with sufficient energy to build large brains, to adopting slash-and burn agriculture that maybe ended the ice age, to inventing the internal combustion engine aiding in the expansion of our food supply and the burning of fossil fuels as our primary energy source, to maybe being on the cusp of a renewable energy revolution that harnesses the fires of the Sun, this was my essay on what fire did for us.

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