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  • If I were to ask you what you think the average human body temperature is, you'd probably respond with 37 degrees Celsius, or 98.6 degrees Fahrenheit.

  • It's a handy number to know if you're trying to game the thermometer to get out of school.

  • But new studies have uncovered that the rial average human body temperature is actually lower than that, and it's dropping.

  • So where does this classic number of 37 degrees Celsius even come from anyway?

  • Well, in 18 51 a German doctor named Carl Wunderlich conducted a years long study.

  • He went room to room in his hospital with a thermometer, taking the temperatures of some 25 different patients to try and pin down the average human body temperature.

  • And he did 17 years later when he published a paper with that well known metric of 37 degrees.

  • He also gave us the first quantitative measurement for determining if someone has a fever 38 degrees and above.

  • That's a favor, baby, and then for the next 140 years, we just accepted this number as correct.

  • Despite the fact that Doctor of Wonderlic collected this data using a comically large foot long wooden thermometer that had to be held in a patient's armpit for 20 minutes.

  • Because, believe it or not, portable thermometers small enough to fit under your tongue weren't invented until 18 66.

  • So it wasn't until the 19 nineties that another doctor decided to revisit this question using more modern equipment.

  • And he found that, yeah, the average human body temperature is actually around 36.8 degrees Celsius on it varies throughout the day throughout someone's hormonal cycle throughout someone's lifetime.

  • So determining whether or not someone actually has a fever depends on a lot of different factors, which is pretty important to account for in a clinical setting.

  • And then ah, 2020 study out of Stanford University took hundreds of thousands of measurements and found that the average body temperature was around 36.4 degrees Celsius.

  • This made them ask, what if this drop in average temperature isn't entirely due to the difference in thermometer accuracy, but is instead because average human body temperature is actually falling?

  • To answer this question, they embarked on a fascinating research journey that took a historical view of human temperature data in the U.

  • S.

  • They used huge existing data sets ones measuring from 18 60 to 1940 1971 to 1975 2007 to 2017.

  • To get a sense of how human body temperature may have changed over the past 150 odd years.

  • And each of these groups, after adjusting for age, height, wait and other variables show a clear decrease in average temperature over time.

  • There's also a drop between groups as we move from past to present.

  • Even with groups were comparable thermometers were used, so it's clearly not just in equipment issue.

  • So what he's going on?

  • The researchers hypothesize that this decrease in average body temperature over time could be due to a decrease in resting metabolic rate.

  • Essentially, that's how hard your body is working when at rest.

  • They also take it one step further, saying this reduction in resting metabolic rate could be do toe lowered overall inflammation.

  • See, modern populations typically have lower chronic infection, better dental hygiene and just generally improved living in hygiene standards.

  • This could be why people in wealthier countries like the U.

  • S.

  • Are experiencing this drop in body temperature over time.

  • But there's other data that throws that hypothesis off because another recent study tracked the average body temperature of over 5000 members of the demonic, a community in the remote Bolivian rainforest.

  • That doesn't have as much access to that modern health care that the Stanford study proposed as the potential cause of the temperature drop.

  • And even still, the average Toumani body temperature in 2002 was around 37 degrees Celsius, while the 2020 average was 36.5.

  • So now we have a clearly documented decrease in body temperature in populations that are in very different parts of the world, and we still don't know exactly why it could still be due to that improvement in healthcare and sanitation that we mentioned already.

  • It could be due to greater temperature control of our surroundings through things like electric fans and air conditioning.

  • It could be because people are less active than we were 200 years ago and get this.

  • Some scientists have even suggested that using MAWR antibiotics has reduced our bodies microbial diversity so much that it's had an impact on our overall temperature like because we no longer have the heat from all those microbes were now colder people, which is totally wild, so there's still lots to explore here on board.

  • Whatever the reason, the fact remains, no matter how dorky you may feel like you are, humans are getting cooler over time.

  • On speaking of human body temperature, one place you really want to keep cool is the Australian Outback.

  • Be sure to check out lightspeed, our new docuseries on an incredible solar car race across the continent.

  • New episodes will be released every Monday through January 4th.

  • And make sure you subscribe to seeker so you don't miss one.

  • Thanks for watching, and I'll see you next time.

If I were to ask you what you think the average human body temperature is, you'd probably respond with 37 degrees Celsius, or 98.6 degrees Fahrenheit.

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