Humans Getting Colder

[Huckleberry of Yore]

https://www.popsci.com/story/health/body-temperature-dropping-history/?linkId=80609907

The study suggests that the average "normal" or healthy human temperature has dropped over a couple of centuries.

If it's true I'd guess the major contributing factors are nutrition and general cleanliness both resulting in less infectious activity for the immune system to deal with.

Still, I wonder if evolution has hidden tricks up its sleeve.  Could there be genetic "cycles" experienced through generations?  I've heard some traits skip generations; twins, and the widow's peak, for example.  In the case of immune response or cell metabolism, perhaps nature has found it useful to "dither" biological functions to give the population a better chance at survival, a type of optimization.  Even in that case, it seems unlikely that the population would be synchronized.  I think.

[swansont]

If people have been getting taller over this span (better nutrition) then some basic thermodynamics might be a variable. Dud I miss something that addressed bias in any significant way? 

[Huckleberry of Yore]

I didn't see it but only read the article, might try to find the actual study.  Perhaps they recorded height and weight in the datasets.

Another factor I considered, is that over that time have people been living in warmer houses?  I have my winter thermostat at 65F which is low I think, but much higher than say my parents endured.  Perhaps the body adjusts to the ambient conditions to which one is exposed to, over a lifetime.

Looks like the study is here:

https://elifesciences.org/articles/49555

Edited January 21, 2020 by Huckleberry of Yore
Added link.

[Roamer]

40 minutes ago, Huckleberry of Yore said:

Another factor I considered, is that over that time have people been living in warmer houses? 

Not unlikely, i was thinking more affordable clothing.

[Huckleberry of Yore]

Could there be a link to the Flynn Effect, which suggests IQs appear to be rising?  Surveying the Wikipedia article, the effect is a bit controversial, and the data doesn't seem to go back 150 years.

[Ken Fabian]

Body temperature can be different according to diet. A lower calorie diet can cause a drop in body temperature. https://source.wustl.edu/2011/05/restricting-calories-lowers-body-temperature-may-predict-longer-lifespan/

[Huckleberry of Yore]

10 minutes ago, Ken Fabian said:

Body temperature can be different according to diet. A lower calorie diet can cause a drop in body temperature. https://source.wustl.edu/2011/05/restricting-calories-lowers-body-temperature-may-predict-longer-lifespan/

It'd be interesting to have more details about what exactly the "calorie restricted" diet was, what and how much did they eat.  Still, the article suggests longevity may be a consequence of genetics:

"The researchers also note that in an unrelated study called the Baltimore Longitudinal Study of Aging, scientists found that men who had lower core body temperatures, probably for genetic reasons, lived significantly longer than men with higher body temperatures."

[swansont]

8 hours ago, Huckleberry of Yore said:

Could there be a link to the Flynn Effect, which suggests IQs appear to be rising?  Surveying the Wikipedia article, the effect is a bit controversial, and the data doesn't seem to go back 150 years.

There can be biases in either set of samples, but I have a lot more confidence in the ability to measure temperature consistently than the ability to measure IQ consistently. Especially since difficulty in measuring IQ is a known problem.

7 hours ago, Huckleberry of Yore said:

It'd be interesting to have more details about what exactly the "calorie restricted" diet was, what and how much did they eat.  Still, the article suggests longevity may be a consequence of genetics:

"The researchers also note that in an unrelated study called the Baltimore Longitudinal Study of Aging, scientists found that men who had lower core body temperatures, probably for genetic reasons, lived significantly longer than men with higher body temperatures."

That could be because there is a common cause for both, and not necessarily that the lower body temp is the cause of anything.

[studiot]

I don't know (or want to know) who the hell Bonner Corp are but the OP link takes me to  a webpage called 'consent form' that requires me to accept unspecified uses by said Bonner Corp of my data, before I can proceed further. There is no evidence or promise of ever getting to the article.

[swansont]

9 minutes ago, studiot said:

I don't know (or want to know) who the hell Bonner Corp are but the OP link takes me to  a webpage called 'consent form' that requires me to accept unspecified uses by said Bonner Corp of my data, before I can proceed further. There is no evidence or promise of ever getting to the article.

here's a cleaner (I hope) link

https://www.popsci.com/story/health/body-temperature-dropping-history/

[J.C.MacSwell]

11 hours ago, Huckleberry of Yore said:

https://www.popsci.com/story/health/body-temperature-dropping-history/?linkId=80609907

The study suggests that the average "normal" or healthy human temperature has dropped over a couple of centuries.

If it's true I'd guess the major contributing factors are nutrition and general cleanliness both resulting in less infectious activity for the immune system to deal with.

Still, I wonder if evolution has hidden tricks up its sleeve.  Could there be genetic "cycles" experienced through generations?  I've heard some traits skip generations; twins, and the widow's peak, for example.  In the case of immune response or cell metabolism, perhaps nature has found it useful to "dither" biological functions to give the population a better chance at survival, a type of optimization.  Even in that case, it seems unlikely that the population would be synchronized.  I think.

Pretty doubtful. We're all in different parts of the cycle, are we not? Pretty much randomly. And would we even be on the cycle if our parents weren't both on the same part...which is most likely?

Even with a "male cycle" and "female cycle" we'd all be at different points.

[dimreepr]

14 hours ago, Huckleberry of Yore said:

Still, I wonder if evolution has hidden tricks up its sleeve.

What makes you think evolution is a thing?

[Huckleberry of Yore]

1 hour ago, dimreepr said:

What makes you think evolution is a thing?

Not sure what you are asking.  But as an example, calorie restriction appears to be a novel way for evolution to protect a population experiencing food scarcity.  A similar mechanism has been suggested where adolescents' transition into puberty may be accelerated in good times and delayed in times of famine.  So I was just considering what underlying genetic process might explain a trend of lower body temperatures; specifically, if inter-generational mutations are not entirely random.  (I had assumed such mutations were random, but perhaps I'm mistaken, which is often the case.)

[dimreepr]

20 hours ago, Huckleberry of Yore said:

Not sure what you are asking.  But as an example, calorie restriction appears to be a novel way for evolution to protect a population experiencing food scarcity.

evolution just explains what happens when inter-generational mutations are entirely random. So any trend of lower body temperatures is an accident, not evolution protecting us.