Fire has been part of the evolution of the entire history of our planet. What is fire/combustion technically? Combustion is a rapid chemical reaction, accompanied by flame, which releases light and more importantly heat. A fire needs three elements, which include heat, fuel, and oxygen, which we refer to as the fire triangle. The combustion process produces vast amounts of energy; however, the lack of reaction to carbon and the inertness of oxygen, determines how easily a fire will start. For instance, if there is too much moisture in the fuel, it will be harder to light a campfire or any other type of fire.
Research shows that hominids were building fires over a million years ago, which not all researchers believe. The research surmises that the transition of the use of fire correlates with the origin of Homo erectus from a few hundred thousand to 1.9 million years ago. Either way, at this point in history, the brain sizes began to expand, which made the hominid taller and smarter.
Hominids began by exploiting their foraging efforts to find food, by naturally occurring wildfires that would spring up from time to time. They were able to find cooked food such as tubers and rhizomes, which reduced the cost of processing the food, as it broke down fiber, making them easier to eat. Once hominids began to use fire for cooking, they figured out how to use it for warmth, warning off predators, and eventually they were able to use fire in manufacturing of tools and weapons.
In this article, we will discuss when we began using fire, the evolution of cooking, genetic mutation, smoke and disease, the importance of fire on humanity, and the medical applications of fire.
A. The Earliest Example of Hominid Fire
As discussed above, many researchers debate on the exact time in history when hominids began using fire. However, there is now hard evidence of one-million year old charred bones and plant remains, which hominids used in fire making.
Archaeologists investigated South Africa's Wonderwerk cave from the 1970's through the 1990's, finding Acheulean tools such as stone hand axes. In 2004, studies started up again in the cave and they were looking for other signs of hominids using fire. They came up with many signs of fire, including charred bones and burnt plants, as previously mentioned. The researcher found that the shape of the bone fragments and the level of preservation of the burned plants indicated that someone burned them inside of a cave. The new research involved the examination of the bones, plant ash, and cave sediment at a microscopic level, which revealed information that many archaeologists do not normally look for when finding new sites.
The research in 2004 also uncovered ironstone with fractures on early hominid tools that is indicative of heating. Using a technique called a Fourier transform infrared micro-spectroscopy; they were able to determine that the materials found in the cave were heated to over 900 degrees Fahrenheit, which indicates that hominids were using fire well before many researchers thought they did.
B. Evolution of Cooking with Fire
Since the beginning of our existence, humans have relied on two basic tools for survival, language, and fire. By cooking, early humans made more calories available from the existing food and reduced the caloric cost of digestion. This was also the technological breakthrough, which allowed humans to support a bigger brain. Cooking may also have helped to shape our society and our mating system.
Chimpanzees eat many raw foods that we as humans cannot eat, suggesting that hominids evolved away from that ability. In fact, people today that only eat raw food normally do not get enough calories, until they break it down such as in a blender. The blender acts as a pre-digestion device for modern day humans. We as humans have evolved to cook our food and there is a possibility of starving to death even while eating only raw food. Many people in the wild can only survive for a few months without cooking their food, even if they can obtain protein from nuts, fruits, and berries. Evidence suggests that modern humans that eat only raw food will often become underweight and some women may even lose their menstrual cycle.
Cooking provides different chemical processes for starches, meats, and other connective tissues, which increase the amount of calories in the food that is actually available to the human digestive system. Cooking our food also reduces the energy cost of human digestion. For instance, gorillas have to chew their food all day to absorb enough energy to survive for that one day.
There is only a fraction of the calories from raw starches and proteins absorbed by the body, directly by way of the small intestine. The remaining calories pass into the large bowel and break down by way of microbes, while consuming many calories for themselves. When we cook the food, it enters the colon mostly digested. The same amount of calories that our bodies ingest is around thirty percent more energy and comes from cooked oats, wheat, and potato starch as compared to eating them raw. It is not enough to consume just the calories into the human body, what matters is what happens to the calories once they get into the human body. After subtracting the calories spent while chewing, swallowing, and digesting, the body must determine how much useful energy it provides and what to do with it in the human body.
Calories from food will only carry the human body so far, as we are constrained by our energy budget. For most humans, the calories we burn power the heart, digestive system and especially the brain, silently moving molecules around, within, and among the one hundred billion cells contained within a human body. A human body at rest dedicates around one-fifth of its energy to the brain, regardless of brain activity. Therefore, the great leap in our brain size almost two million years ago had to either come from added calories or diverted from another function in the human body.
Cooking not only includes heat but also mechanical processes such as grinding and chopping our food, which helps in human digestion, so our bodies can extract more energy from our food, and has less energy expenditure when digesting the food. Cooking our food breaks down collagen, which is the connective tissue in meat, and softens the cell walls of plants in order to release the starch and fat.
The development of a large brain relative to the stomach size of a human comes from cooking, as it frees up more metabolic energy available to do other things, such as hunting during prehistoric times. There is a hypothesis called the "expensive tissue hypothesis", in which scientists believe that adding meat to our diet was the breakthrough for human evolution. The amount of calories needed to fuel bigger brains, came at the expense of energy-intensive tissue located in the stomach, which was also shrinking around the time of hominids beginning to cook food. Cooked food is easier to digest, which made the hominid stomach shrink, freeing up energy they could devote to the fueling of the evolution of bigger brains, which are very expensive to maintain in terms of energy expenditure. Brain tissue requires twenty-two times as much energy to maintain as the equivalent amount of muscle tissue.
Cooking also frees up time that we can spend in other pursuits. For instance, many ape species will spend most of their day chewing, not expending much energy; which is not an activity that produces as much intellect in apes, as it does when humans cook food that allow them the energy to pursue other activities. This supports the theory that cooking may be the breakthrough event in hominid history, which allowed our ancestors to evolve into the modern day human.
C. Genetic Mutations
Scientists identified a genetic mutation within modern humans that allow us to metabolize certain toxins at a safe rate, including toxins found in smoke. However, they did not find the same genetic mutation in other primates including ancient hominids such as Neanderthals and Denisovans. Researchers believe that this mutation occurred in response to breathing in toxic smoke, which increases the risk of respiratory infections, suppresses the immune system, and disrupts the reproductive system.
Other animals that did not master the art of fire may not be the best models in the examination of how we process food and detoxify certain substances. Researchers speculate that a genetic mutation gave modern humans an evolutionary edge over Neanderthals. If the postulation is correct, a mutation may have gave modern humans adaptations to reverse the negative effects of fire and smoke.
A genetic mutation may have given modern humans other adaptations to better handle, or even take advantage of the byproduct of a fire in the food they ate. Investigating a fire's harmful effects and the way in which it shaped human evolution and history may provide us with a good look at the relationship between biology and culture. Maybe we evolved biologically to guard against the harmful effects of inhaling smoke, which in turn may have caused humans to pick up the cultural practice of smoking.
D. Smoke, Fire and Disease
Early humans discovered how to use fire and life became much easier in many ways. They would use the fire for warmth, light, and protection. They also used fire to cook their food, which gave them more energy than just eating a diet of raw food. Socialization became easier, which may have gave way to cultural traditions such as storytelling.
Fire may have made life easier on early humans, but fire also comes with its adverse effects. The smoke would probably have stung their eyes and scorched their lungs. Their food also likely had a coating of char from the fire, increasing the risk of certain types of cancer. In addition, a big congregation of people in one place could easily allow for the transfer of disease.
Studies suggest that hominids may not have been able to adapt to all of the dangers associated with fire and smoke. Fire may have been advantageous for early hominid societies, but it also came with a new type of danger, disease. Scientists believe that the early use of fire may have helped spread tuberculosis throughout a community, which damages the lungs and causes uncontrollable coughing.
Scientists simulated how ancient soil bacteria may have evolved to become highly infectious tuberculosis agents. The probability of the tuberculosis agents emerging was low without the presence of fire; however, when fire was added, the likelihood of tuberculosis emerging jumped by several degrees of magnitude. To this day, it remains one of the deadliest infections ever evolved. The discovery of controlled fire most likely caused a major shift in the way humans were interacting with other humans and the environment, factors known to drive airborne infectious diseases.
Another negative consequence with fire that continues to leave an imprint on humanity includes the inhalation of smoke over the centuries, possibly leading to the discovery of cultural smoking.
E. Importance of Fire on Humanity
It is an inescapable fact that fire is important in the evolution of human history; however, the extent of the importance has not been explored fully yet. Early hominids probably used fire for warmth, extending their day, hunting, warding off predators and insects, and enabling them to cook their food. Campfires include flickering light, crackling sounds, warmth, and a very distinctive smell, which sometimes has relaxation effects, which probably promoted socialism among communities.
In the wild, the sight or smell of smoke will reveal a cook's location for a very long distance, which would potentially attract hungry humans to the cook's location. It is easy to imagine the effect of fire on Homo erectus during the early years of use. Females were smaller and physically weaker than the males at this time. The larger males who wanted food also bullied them for food. Therefore, the females would obtain the protection of a male by forming a special bond with them. The female's bond with her male protected the food she collected from other males, in exchange for a portion of that male's food. These bonds were critical for the successful feeding of both genders. They generated a particular kind of evolutionary psychology that shaped the female-male relationship required for reproduction that lasts to this day.
