The invention that made us human: Fire
Did fire change the development of the human brain?
- The earliest evidence for fire dates back nearly 440 million years.
- Our hominin ancestors first used natural wildfires to flush out prey and forage for food.
- Richard Wrangham's cooking hypothesis suggests that a ready supply of cooked food allowed the Homo lineage to develop its large, complex brains.
Of humanity's greatest inventions, fire remains as important today as in the time of our ancient ancestors. If not as apparent.
We have replaced the hearth with electric ovens and central heating, but the burning of fossil fuels accounts for 63.5 percent of U.S. electricity generation. We still heat our homes and cook our food with fire — just in a more roundabout manner.
We even use fire in ways our ancestors couldn't have imagined. The internal combustion engine has replaced animals and our own wobbly legs as the preferred method of travel. We can go farther in a day than the vast majority of our ancestors did in a lifetime and even escape the confines of our planet. Thanks to fire.
But fire has done more than create the energy that makes our lives comfortable. By one Harvard professor's account, fire altered the course of our evolution.
Fire, a brief history
Wildfires, such as this one at Yellowstone National Park, have been a recurring phenomenon for more than 440 million years.
First, some Chem 101. Fire requires three elements for its reaction: oxygen, a fuel, and a heat source. Since two of the three elements are provided naturally by plants, the history of fire became intricately tied to them.
Some of our earliest evidence for fire goes back 440 million years to the Silurian period, when Earth's climate stabilized and plants and animals began to move to land. Of note, this period provides the earliest fossil evidence of vascular plants.
From this point, fire becomes a recurrent phenomenon with times of high and low activity based on environmental conditions. During the Carboniferous period, atmospheric oxygen hit a record high of 31 percent and plants spread across the supercontinent Pangea, so charcoal records suggest a lot of fire activity during this period. Conversely, the pittance of charcoal from the Triassic period suggests low atmospheric oxygen and fewer plants.
Jumping a few million years to the late Miocene, hominins moved to the grasslands and begun to further diverge from their ape relatives — likely due to the difference between the African savanna and the dense jungle. Here, they would have also encountered wildfires with far more regularity.
We didn't start the fire
Prometheus Brings Fire to Mankind by Heinrich Fuger. Our early reliance on nature for fire draws parallels to later mythologies.
Low-hanging references aside, Billy Joel was on to something. Popular culture conjures the image of a caveman banging two stones together. Sparks fly, and then the eureka moment. Yet, our ancestors' first usage of fire probably wasn't a matter of control or invention. It was more likely opportunistic.
In a review for the Royal Society Philosophical Transactions B, J.A.J. Gowlett hypothesizes that hominins took advantage of natural wildfires for foraging. "For hominins," he writes, "benefits could include retrieval of birds eggs, rodents, lizards and other small animals, as well as invertebrates. Although fire does not create such resources, it renders them far more visible, and chance cooking might well improve their digestibility."
Gowlett notes that analogues to this behavior exist in the natural world today. Savanna chimpanzees use fires to locate resources, and several bird species follow fires to snatch up any prey flushed out by the smoke and flames. There has even been anecdotal evidence of some raptors, such as Australia's "firehawks," picking up smoldering wood from one fire and carrying it elsewhere to start another.
Early hominins would have also begun to discover fire's properties by observing and interacting with these blazes. For example, if a meaty morsel proved too raw, they may have learned to place it on embers to continue the cooking process.
Given our early reliance on nature for fire, it's little wonder that the theft of fire theme has appeared time and again in the world's mythologies.
But we kept it burning
It's difficult to follow the development of hominin control over fire because of what Gowlett calls its "disappearing act." Fire isn't as well preserved in the archeological record as, say, middens or flint tools. And progress was incremental, with fire control being learned in different places at different times.
Certain archeological sites have proffered a bounty of stone tools, suggesting long-term quartering. Such occupancy could mean hominins learned to at least maintain fire as far back as 2.5 million years ago. But direct evidence is scarce.
As we move forward, we see more evidence of hominins' control over fire. Archaeologists have discovered campfire traces and charred animal and plant remains at Wonderwerk Cave in South Africa. These have been dated back to approximately one million years ago. And the oldest known hearth, found at Qesem Cave, Israel, dates back more than 300,000 years ago.
Interestingly, archeologists aren't sure which hominin species got cozy at Qesem. "It is clearly different than [Homo] erectus and has affinities of both [Homo] sapiens and Neanderthals," Ran Barkai, Tel Aviv archaeologist, told National Geographic. "Since Neanderthals appear very late in the Levant and are of European origin, and since the Qesem teeth bear more resemblance to early Homo sapiens in the Levant, we believe they are closer to Homo sapiens."
Hearths and campfires tell us hominins could maintain fires for cooking and warmth. They do not, however, prove our ability to create fire. After transferring a brand from a wildfire, a tribe member could have been given fire duty and tasked with fueling the fire to prevent its extinguishing.
Good evidence for fire creation appears around 120,000 years ago, when hominins had access to twine, a requisite to developing the bow drill. And archeologists have dated two glues used in hafting, bark pitch and gypsum plaster, to between 50 and 100 thousand years ago. Neither of these can be prepared without fire.
At this point, Gowlett argues, the invention of fire belongs to our ancestors. "[A]n understanding is emerging that fire use is not a single technology or process, but that several scales of use, and probably several intensifying technologies, evolved over a long period, intertwined, and sometimes eventually became bound together," he writes.
Fire (and food) for thought
Cooked meats are easier to chew and digest; as a result, our bodies can extract more nutrients from the same amount of meat. Similarly, cooking vegetables increases levels of healthy stuff like antioxidants. That's because the cooking process breaks down the plants' cell walls and, like meat, makes them easier to digest and process. (Though, it is a tradeoff. Some veggies are healthier raw, and it depends on how you cook them.)
Wrangham argues that the ability to create cooked foods shaped the brains and bodies of our Homo ancestors. Since our ancestors spent less energy digesting foods and could draw out additional nutrients, they had more to nutrients to spend, and evolution spent those dividends on maintaining larger brains — not to mention smaller teeth and jaws. Larger brains allowed us to process more information, create more dynamic social groups, and adjust to unfamiliar habitats. All of which benefited us evolutionarily.
With that said, the cooking hypothesis has its detractors. Some argue there is little proof that humans were cooking or maintaining fire in concurrence with Homo erectus' brain-size explosion (roughly 1.5 million years ago). It's also possible that a diet of raw meat and veggies could have provided the necessary nutrients for bigger brains.
Other hypotheses exist to explain the increase in hominin brain size. The social brain hypothesis, for example, argues our brains evolved to meet the challenges of living in large social groups. But even here, fire plays a role. Remember that before our ancestors could ignite fire, they had to maintain it. This required a division of labor, which is only possible in a species with a highly structured social network.
Fire may or may not ultimately prove to be principal in our evolutionary development. For any such hypothesis more evidence is needed — though fire, cooked food, and social networks likely all played a part.
Without a doubt, fire has proved a primary mover in the evolution of civilization. It helped us migrate to climates that would otherwise prove inhospitable. It was essential to the development of cuisine, agriculture, metallurgy, architecture, and a host of other industries. In short, the invention of fire has taken humanity places no other species has gone.
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Whether or not women think beards are sexy has to do with "moral disgust"
- A new study found that women perceive men with facial hair to be more attractive as well as physically and socially dominant.
- Women tend to associate more masculine faces with physical strength, social assertiveness, and formidability.
- Women who display higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, are more likely to prefer hairy faces.
Beards and perceptions of masculinity<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg0MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzkxMjM3N30.cH-GqNwP5GVqvstgJWAhBPn1B_lYpVEAI0I7iax7EQw/img.jpg?width=1245&coordinates=0%2C1900%2C0%2C849&height=700" id="caae6" class="rm-shortcode" data-rm-shortcode-id="cb0a355a4e8e1899789bc45f3f7aef56" data-rm-shortcode-name="rebelmouse-image" />
Photo Credit: Wikimedia<p>The study used 919 American (mostly white) women ages 18-70 who rated 30 pictures of men they were shown with various stages of facial hair growth. The photographs depicted men with faces that had been digitally altered to look more feminine or more masculine, with a beard and without a beard. The women rated the men according to perceived attractiveness for long-term and short-term relationships. The study found that the more facial hair the men had, the higher the men were rated on their attractiveness, particularly for their suitability for a long-term relationship.</p><p>Part of this might be attributed to facial masculinity — i.e. protruding brow ridge, wide cheekbones, thick jawline, and deeply set narrow eyes — which conveys information to a woman about a man's underlying health and formidability. Women tend to associate more masculine faces with physical strength and social assertiveness. It can also indicate a man with a superior immune response. The researchers suggested that their findings favoring bearded men could be due to the fact that facial hair enhances the masculine facial features on a man's face, like creating the illusion of a thicker jaw line. This could communicate direct benefits to women like resources and protection that would enhance survival among mothers and their infants. In other words, while a beard doesn't mean superior genetics in and of itself, it might be a primitive, ornamental way of saying, "Hey girl, I'm a testosterone-fueled lean, mean, pathogen fighting machine." <br></p><p>It could also be that a beard becomes its own destiny. The researchers in this study cite prior research that found that by growing a beard, men felt more masculine and had higher levels of serum testosterone, which was linked to a higher level of social dominance. They also tended to subscribe to more old-school beliefs about gender roles in their relationships with women as compared to men with clean-shaven faces.<span></span><br></p>
What does disgust have to do with beard preference?<p>Obviously, not all women dig beards. The researchers were particularly interested in what traits make a women prefer bearded men over clean-shaven faces. They looked into several factors including a woman's disgust levels on various concepts, her desire to become pregnant, and her exposure to facial hair in her personal life. </p><p>According to the study, women who were not into facial hair were turned-off by potential parasites or other critters they imagined could be in the hair or skin. Women ranking high on this "ectoparasite disgust" scale might have viewed beards as a sign of poor grooming habits. However, women who ranked higher in levels of "pathogen" did find the bearded men to be desirable, possibly because they perceived beards as a signal of good health and immune function. An intriguing discovery in the study was links to morality. Women who displayed higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, were more likely to prefer hairy faces. The authors opined that this could reflect a link between beardedness, politically conservative outlooks, and traditional views regarding performances of masculinity in heterosexual relationships.</p>
Additional findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg1My9vcmlnaW4uZ2lmIiwiZXhwaXJlc19hdCI6MTYyNDI1NjUyOX0.P9B8WbmJR0q4nfzYZKbuNSA-2SAigVWJgrQE-_Gxlds/img.gif?width=980" id="49143" class="rm-shortcode" data-rm-shortcode-id="2ed3b1d6f20fc170bf2974646e565e8d" data-rm-shortcode-name="rebelmouse-image" />Giphy<p>The correlations that existed between married and single women's rating on the attractiveness of beards were not particularly clear, although the researchers noted that single and married women who wanted children tended to find beards more attractive than the women who didn't want children. They also found that women with bearded husbands found beards to be more attractive, which might indicate that social exposure to beards influences how desirable they are perceived of as being. Or it could be that men with wives who like beards grow beards.</p><p>It's important to note that culture plays a huge role in how attractive women perceive certain male characteristics as being. This study looked at a small, culturally specific group of American women, so no big, universal claims should be made about masculinity, facial hair, and male desirability to women. However, research like this is important in highlighting how human grooming decisions are driven by much more than fashion trends. Sociobiological, economic, and ecological factors all play a part in the way we choose to present ourselves.</p>
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