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Spanning The Globe- July 2023

It’s time to go spanning the globe for anatomy news and notes:


Infographic!


We love a good infographic as much as anyone and the folks at Visual Capitalist have published one that’s right up our alley: “Human Evolution: From Protocells to People.”


See the full infographic here.


As the title suggests, the narrative starts with protocells and moves through multicellular life, animals, fish, tetrapods, mammals, Great Apes, and Homo sapiens.


An accompanying article highlights the key factors in this long process. It also makes a few key points about the future.

“As humans continue to evolve, we can expect to see significant changes in our physical and cognitive abilities over the next 10,000 years,” states the article. “With the rise of technology and the increasing interconnectedness of the world, we may see a shift towards a more globalized and homogeneous human population, with less genetic diversity. This has been described as ‘The Great Averaging,’ where genetic diversity minimizes and we start to become more alike.”

As the old saying goes, “time will tell.”

(It always has.)


Mudskippers


Blinking eyes! They are critical to life here on land as we humans move around a world of dust and grit and blowing winds. Ask any mammal or tetrapod and they would all likely endorse the importance of good, working eyelids. But how did that feature of anatomy evolve?


Researchers at Georgia Institute of Technology released a study that look

at an amphibious fish called the mudskipper, a fish that blinks. The study is titled, “The origin of blinking in both mudskippers and tetrapods is linked to life on land.” And it strengthens our understanding that the blink, for many organisms, was in response to all the new pressures that came with the shift out of water.


It's important to note that mudskippers developed the ability to blink on their own. The ability of tetrapods to do so was a separate accomplishment. And when you go to check out a video, you’ll see it’s an entirely different blink!



To study the blinking mudskippers,

researchers used a large tank and high-speed cameras to see how the strange-looking fishes move between land and water. (Mudskippers can “walk” across land on their fins.) The researchers found that the mudskippers barely blinked under water but blinked much more frequently on land.


And they found that researchers found that mudskippers blinked for the same reason that tetrapods do—to wet, protect and clean their eyes.


Surviving Heat


We touched on issues of heat on the human body last year in a blog post about the hypothalamus.


Now a study from the United Kingdom is working to find the human body’s upper limits for withstanding high temperatures. It’s kind of important, one might think, because climate change is bringing extremely hot temperatures around the globe.


The researchers found that some people experience an increased metabolic rate at extremely hot environments—and that’s not a good move for the body because increased metabolism means the body is producing even more heat. Other individuals, however, stayed cooler. To conduct the study, researchers submitted a small group of people to temperatures that reached 122 degrees Fahrenheit and up to 50% humidity for an hour.


As we all likely know, humidity doesn’t help the body’s ability to cool itself because sweating involves evaporation of water from the body, which is harder to accomplish when the air around you is wet.


So at what point is the body unable to cool itself?


Compared to the baseline of 82 degrees, the study found that participants experienced a 16% increase in heart rate at 104 degrees and a 64% increase at 122 degrees with 50% humidity.


So what’s the upper limit? Well, no test subjects perished in this study so we don’t really know. (That’s a good thing.)


But let’s hope that we don’t find out from the natural causes as a result of global warming. The study was published in early July, 2023—following a month that was the hottest on record in the UK.

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