Lindau Longread: Illuminated Storytelling

Apr 9, 2015

Photo by Jason Hickey, distributed udner Creative Commons (CC BY 2.0).

By Jalees Rehman

The history of humankind is also the history of controlling fire. Myths and folklore from all over the world attest to the central role that fire has played in our history. Matarisvan in the Hindu Rig Veda and Coyote in Native American legends are credited with gifting fire to humans. The Greek legend of Prometheus recounts how Prometheus – always looking out for human welfare and development – angered Zeus by sharing the secret of fire with humans. As a punishment for his humanist deed, Prometheus was chained to a rock. He endured the pain of an eagle preying on his liver, which would regenerate each day and thus perpetuate the daily trauma of having part of his liver ripped out by an eagle. The magnitude of this Promethean torment only underscores the significance that the Ancient Greeks attributed to the usage of fire by humans.

We do not need to rely on ancient myths to understand the importance of fire in our history. The discovery of burned bones and plant remains in a cave in South Africa suggests that our hominid ancestors used controlled fire at least one million years ago, and there is ample evidence for regular fire usage approximately 350,000 years ago. Was controlled fire just one of the many tools that hominins harnessed and used or was fire essential for the evolution of our species? There are obvious benefits to using fire such as staying warm when it is freezing cold outside or fending off potential predators. The primatologist Richard Wrangham famously formulated the “cooking hypothesis” which stated that central benefit of fire usage was that it enabled hominins to cook their food. Cooked food allowed our ancestors to increase the amount of energy their bodies could extract from food. Instead of wasting energy trying to digest raw food, fire-controlling hominins could utilize this additional energy to grow bigger brains and evolve cognitively.

An even more intriguing perspective for the indispensable role of fire has been put forward by the primatologist Frances Burton from the University of Toronto in her book, aptly titled, “Fire: The Spark That Ignited Human Evolution”. Burton does not discount that fire provided warmth and a means for cooking but she proposes that the key benefit our ancestors derived from controlling fire was that it allowed them to generate light. Instead of having to rely on natural sunlight, hominins used fire as a light source at night to artificially extend the day. Burton suggests that the light emitted from campfires changed the hormonal patterns of our ancestors. It suppressed the hormone melatonin which is released by the pineal gland in our brain at night and functions as an important regulator of our internal biological clock. According to Burton, the changes in hormonal patterns by campfires liberated our ancestors from the natural light-dark cycles and seasonality and increased their ability to reproduce.

As intriguing as Burton’s idea is, there is little scientific evidence to back up the notion that light emitted by the campfires of our ancestors was sufficient to propel human evolution forward by affecting internal biological clocks. Humans, like other animals and plants, have an internal biological timekeeping system called a circadian clock. The name “circadian” is derived from “circa” = ‘approximately” and “dian” = “one day” and refers to the fact that our internal clock runs at a period of approximately 24 hours, mirroring the 24 hour day/night cycle of the earth. The internal circadian clock allows our body to anticipate the external time of the day. Our body temperature, hormones and many other important processes in the body would keep on cycling in a 24 hour rhythm even if we were to spend a few days in continuous light or in continuous darkness.


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10 comments on “Lindau Longread: Illuminated Storytelling

  • If you go camping where there is little artificial light, your wake-sleep cycle rapidly syncs with sunlight. You don’t stay up more than a few hours after sunset. This time around the fire is traditionally story-telling time. It would certainly help to build and cement culture.



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  • @OP – As intriguing as Burton’s idea is, there is little scientific evidence to back up the notion that light emitted by the campfires of our ancestors was sufficient to propel human evolution forward by affecting internal biological clocks. Humans, like other animals and plants, have an internal biological timekeeping system called a circadian clock.

    There will soon be plenty of detailed scientific evidence on circadian clocks, to add to earlier work at polar bases:

    http://www.esa.int/Our_Activities/Human_Spaceflight/Blue_dot/Medical_research
    Our bodies know roughly what time of day it is, making us feel sleepy at night. Our biological clock follows Earth’s 24‐hour cycle but reacts to sunlight. In our modern world, many people live outside of the natural cycle, staying up late or working night shifts. As a result, problems with sleeping are common but not fully understood.

    Astronauts experience 16 sunrises and sunsets every day on the International Space Station as it circles Earth. The Station offers a unique place to study circadian rhythms. No other place near Earth offers 90-minute days that put a serious strain on people’s body clocks.

    How his biological clock reacts is of interest to the next generation of astronauts as well as people on Earth who work irregular hours such as doctors and emergency workers. The data will be shared and compared with studies in isolation such as ESA’s Mars500 and in places that experience the opposite to short days, such as the four months without sunlight at the Concordia research base in Antarctica.

    The Circadian rhythms experiment measures an astronaut’s temperature and melatonin, a hormone linked to sleep. Alexander’s readings are measured continuously using Thermolab, a new and patented sensor that monitors temperature without impractical thermometers.

    The findings will help in finding out how to rest effectively and be alert when most needed, a skill that many would benefit from, especially astronauts who need to be ready for spacecraft dockings at irregular intervals.



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  • The science here seems rather poor and inexcusably so. Our circadian rhythms as Professor Sam Berman discovered are driven not by light sensed by the normal rods and cones of our retina but by that detected in some non-imaging ganglions also distributed over the retina with a peak sensitivity in the range 485 to 491nm (turquoise, I guess). These same light sensors are the ones that drive our iris dilation control, and can be imagined to derive from very early ocelli type sensors in some bygone, aquatic state or other.

    Camp fires are not great generators of turquoise so the stimulation of the these photo-sensitive ganglions by their already gloomy light seems very unlikely indeed.

    This does, however, explain why candlelight is quite so romantic. Not just flame-softened and fluttery light on our faces but light quite unable to to make our irises contract. We look at each other, pupils still fully dilated by the lack of turquoise, but not, as we fondly imagine, from an oxytocin surge.



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  • Hi Phil,

    As I mention in the essay, Burton offers very little evidence to support the circadian hypothesis. I am not so concerned about the wavelength. I think the low level of light intensity that reaches individuals at a campfire is the major weakness regarding her hypothesis.

    Regarding wavelength sensitivity in humans: Multiple groups have identified circadian effects in humans using blue (446-483 nm) light. My own circadian research focused on algae, which are exquisitely sensitive to blue light. However, Christian Cajochen and Anna Wirz-Justice, who have really amassed an extraordinary amount of data on human circadian clock sensitivity, routinely observe melatonin suppression and/or circadian clock phase shifts with blue light pulses. Here is a link to one of their open-access papers: Acute exposure to evening blue-enriched light impacts on human sleep.

    Thanks,
    Jalees



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  • Thanks for the paper. Jalees. I shall read it with interest. I note in the abstract-

    Our data suggest that exposure to blue-enriched polychromatic light at relatively low room light levels impacts upon homeostatic sleep regulation

    which sort of implies that for homeostatic sleep regulation, low light level (~25lux) is not the problem so much as blue deficiency. (I do though wish they had worked with cleaner light sources.)

    This stuff is finding application in the field of office lighting where eco concerns are dropping ambient levels from 300lux to 100 and below in some experiments (but 300 to 600lux at the desk) but with “cirtopic” blue added to the ambient for better circadian syncing.

    I do, though, take your point. Whatever, camp fires really can’t cut it.



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  • Thanks for your thoughts, Phil. I agree with you about the need for more studies with “cleaner” light, i.e. light with well-defined wavelengths. This is also a big focus area in light pollution research. Due to the fact that the wavelength sensitivity of vision and the circadian clocks differs (as you pointed out in your original comment), it would be best to use monochromatic light sources at night that allow us to see but do not affect the circadian clocks.



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  • phil rimmer
    Apr 11, 2015 at 8:06 am

    Our data suggest that exposure to blue-enriched polychromatic light at relatively low room light levels impacts upon homeostatic sleep regulation

    which sort of implies that for homeostatic sleep regulation, low light level (~25lux) is not the problem so much as blue deficiency. (I do though wish they had worked with cleaner light sources.)

    This stuff is finding application in the field of office lighting where eco concerns are dropping ambient levels from 300lux to 100 and below in some experiments (but 300 to 600lux at the desk) but with “cirtopic” blue added to the ambient for better circadian syncing.

    This looks like giving interesting details. With research at polar bases and on the ISS, plus targeting specific areas of the spectrum, prospects for building an overall picture look promising.



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  • While I accept the counterargument that firelight didn’t necessarily contribute to human evolution via the circadian rhythm, I remain unconvinced that it couldn’t have contributed in other ways. Perhaps more importantly to humanity today, it surely contributed to the evolution of society. That extra hour or three just before drifting off to sleep is the perfect time for language to have evolved, for planning to occur, for councils to be held, for stories to be told. It’s time that couldn’t be properly spent in most physical work (hunting/gathering), but could easily be spent in intellectual work.



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  • Wil, the role of campfires in promoting society, language and communication are all potential ways by which the extended day could have contributed to human evolution.

    I focused on the storytelling aspect in my essay because this is what the research on modern day hunter/gatherer societies has shown, but I agree with you that the consequences of storytelling could also include societal bonds.
    Thanks,
    Jalees



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  • Caspari and Lee in a paper from around 2005, 2006 observed that in the Aurignacian the appearance of old folk (grandparents) in the archeological record shot up by 400%. Whilst I have my own theories about what was going on, it is notable that this period included a great flourishing in all aspects of the culture including art. Old folk have always been available to look after children but something specific appears to have happened then that made old folk more valuable, worth feeding still when they couldn’t feed themselves. If language became much more useful then with the advent of abstract thinking, emotional content and future and past tenses, (perhaps in concert with art and its reification and abstraction of the world) then maybe old folk could at last “sing for their supper”, convey advice and experience and extend it with made up stuff when they ran out. (“Not that one again, Gramps!” “Ah, but did I ever tell you about the time when……”)

    I wonder if camp fires made an increased appearance in this period also?…..



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