For some time now I have been writing in this space that our Achilles Heel as a species may have come at a fork along our evolutionary biology pathway many millions of years ago. Relatively few others of our fellow creatures decided to follow our lead, and for good reason. We decided to sweat.
Having sweat glands conferred an immediate advantage, the type of advantage our kind also seems to select for, rather than thinking through the more distant implications. Only primates — such as humans, monkeys, and apes — and horses have skin covered by sweat glands to regulate their body temperature through evaporation of water. Maximum sweat rates of an adult human can be 2-4 liters per hour or 10-14 liters per day. Dogs and cats, which have just a few such glands, accomplish temperature regulation by panting, which evaporates water from the moist lining of their oral cavity. Elephants manage it with capillaries in their giant, flapping ears (Woolly Mammoths, unfortunately, lacked those and were hunted to extinction).
As bipedal athletes, our ancestors could not dash as fast as deer, boar, or zebras but had the advantage of sweat. We could keep up a fast pace longer than our prey could. As the prey overheated, they were forced to slow down. As we overheated, we only needed to refill our water reserve— hence the gourd. It became as important as the spear. Fear, anxiety, stress, and pain can also cause us to sweat because our biological instincts kick in and prepare us to run.
Ugo Bardi teaches physical chemistry at the University of Florence, in Italy. I have been following his writing on biophysical economics, system dynamics modeling, and metahistory for more than 20 years. His blog in English is Cassandra’s legacy. His most recent book in English is Extracted: How the Quest for Global Mining Wealth is Plundering the Planet (Chelsea Green 2014). He was also the author of The Limits to Growth Revisited (Springer 2011).
Mineral treasures that took millions, even billions of years to form are now being squandered in just centuries…www.chelseagreen.com
In essays just this month so far, he seems to have debunked the notion that the Roman Empire fell from climate change, but raised the possibility that its fall caused a climate change; described how Earth’s ecosystem controls climate by the biotic pump; how the mountain Ebih “melted into a vat of sheepfat” in the 3rd Millennium BCE; and how in times of crisis the panicked elite do not react with reasoned debate, but with the usual combination of lies, damned lies, and propaganda.
I was delighted to have the chance to experience Ugo in person when he gave a lovely workshop entitled, La Grande Transizione — Da Dove e Per Dove (The Great Transition — From Where and To Where) at the annual convergence of GEN-Europe in Comune di Bagnaia, Italy, this week. What was surprising was not what he said, because he left many of the questions he raised unanswered, but how he lectures.
How did these small humans in their rowed boats kill these leviathans, he asks. Why didn’t these mammals, who were much faster and stronger, merely swim away? He holds up the gourd.
In whaling, the gourd takes the form of an empty oak cask, attached to a line. If the harpooner can toss a barbed dart into the thick skin of the whale as it passes his boat, the whale is doomed. The barb may cause some superficial bleeding but is not fatal by itself. Attach a cask to its line, however, and now the whale is unable to dive to safety. As it swims, pursued by the rowboat, the drag of the line wears it out. Eventually, the boat overtakes the whale and delivers the coup de grâce, usually by a lance driven through the creature’s heart.
In a 2004 post to the Oil Drum, Bardi wrote:
In his 1878 book, Alexander Starbuck cited several factors for the decline of production of the whale fisheries in times that for him were recent. He seems to have believed that it was not the extermination of the whales that caused the decline but, rather, the increase of the human population which led to “an increase in consumption beyond the power of the fishery to supply.” But it was also clear to him that the cost and the length of voyages had increased beyond reasonable limits. He did cite “the scarcity and shyness of whales” as a problem, but he stops short of saying that the whale stock was depleted beyond recovery. Most likely, the concept of “extinction” was alien to him, as it was to most of his contemporaries.
Our perception problem with crude oil is equivalent to that of Starbuck, and indeed it is perhaps more severe. The concept of the terminal depletion of a mineral resource is alien to us, since there have been no worldwide precedents. In addition, we are apparently just near the midpoint on the production curve, so we still have to experience the peak, the associated price rise, and the decline. What the future has in store is uncertain: perhaps an energy equivalent of the “rock oil” of Starbuck’s times will materialize in the near future. But if it does not materialize we will have to live with depletion and before long begin to see lamps going out.
So what is our lesson here? Bardi never really got to that, but my takeaway was that we humans have immense technological hubris but little empathy. Bardi said we have developed empathy for honeybees, pandas, and whales but are unlikely to do that for mosquitoes and cockroaches. Unless we can imagine ourselves within the web of life, instead of seeing ourselves as its masters, we are doomed.
I think we risk destruction by many separate routes. We can fill our gourds to slake our thirst, but these days the water is likely contaminated with microplastics. The plastic spear Bardi used to illustrate his whale story is killing more whales now when it is discarded than Ahab could have with forged iron at the tip of a wooden pole.
One real problem we will face stems from that evolutionary decision about sweat glands that our ancestors made.
Orcas, thanks to subcutaneous fat stores, can withstand water temperatures ranging from 0° to 30–35°C (32–95°F). Certain species of tardigrade, including Mi. tardigradum, can withstand and survive temperatures ranging from –273 °C (near absolute zero) to 150 °C in their anhydrobiotic state. Humans have no such tolerance.
Certain sharks, tuna, billfishes, birds and mammals, including ourselves, are endothermic, or “warm-blooded” in common parlance. We have a larger number of mitochondria per cell than ectotherms, enabling us to generate heat by increasing the rate at which we metabolize fats and sugars. If we get too hot, we sweat. If we get too cold, we shiver, sit in strong sunlight, bundle in furs, or burn fat faster.
To sustain higher metabolism, we need several times the food intake of ectothermic animals. Endothermism has its advantages, such as a constant core temperature for optimum enzyme activity. We are not only ourselves under the skin but an entire community. Our human microbiome is optimally advantaged at 37°C (98.6°F).
But endothermism also has disadvantages. If we get too hot we try to slow our metabolic burn. That is what happens during sleep when our core temperature drops typically 1°C. It’s also why the greatest threat to life during heat waves may be during the night when bodies cannot stay cool enough to survive.
When relative humidity is 100%, sweating does nothing to cool us. Hotter air can store more water than colder air. When the human body is exposed to constant temperatures of approximately 55°C (131°F) longer than a few hours, death is almost inevitable. In the early stages, we may try to slow heat generation by ceasing activity. If the heat persists, the effects of our diminished metabolism damage our central nervous system first, especially the brain and those parts concerning consciousness; then heart rate and respiration decrease; judgment becomes impaired as drowsiness supervenes, becoming steadily deeper until we lose consciousness. Mammalian muscle becomes rigid with heat rigor at about 50°C (122°F), with that sudden rigidity of the whole body rendering life impossible.
Humans may catch lethal hyperthermia when a wet-bulb temperature (heat index) is sustained above 35°C (95°F) for six hours. In these conditions, if the temperature of the surroundings is greater than that of the skin, the body actually gains heat by radiation and conduction.Peter Sinclair writes: "Stepped outside yet today? Today in the midwest is what a normal summer day will be like in a few decades." National Geographic: "In less than 20 years, millions of people in the United States could be exposed to dangerous "off-the-charts" heat conditions of 127 degrees Fahrenheit or more...."
Sadly, hyperthermia occurs in birds, insects, fishes, land animals, and plants of course, too. The sacred lotus (Nelumbo nucifera) can sustain 20 degrees C (36 degrees F) above air temperature while flowering by breaking down starch in their roots, consuming oxygen at a rate of a flying hummingbird, but lacks a similar ability to cool itself. Many plants do not flower, do not fruit, and do not reproduce themselves when it is too warm.
We will need better tools than gourds if we are going to survive this time. We need to discover empathy. And then plant a whole lot of trees.
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Thanks for a great blog always, read it every week. I have a question unrelated to this post, I have lost a podcast I saved that you recommended many many posts ago. I think you called it your favourite climate related podcast, they interview climate scientists and it is called something ending with FM. Thanks!
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