6
$\begingroup$

Human body temperature is a very complex and tightly regulated system. Hypothermia or fever of only 1-2K (i.e. changes of about 5%) already cause major symptoms and changes of 3-4K (i.e. about 10%) are life threatening. Many humans live under relatively cold outside temperature conditions and maintaining an inside 36-37 degree C in these conditions is very energy consuming (most probably a reason why the body temperature in the periphery is several degrees lower), indicating very strong evolutionary constraints on not changing the core temperature too much (I remember a professor in biology classes in university saying that most fungi have a growth minimum around 37 degree C). However, other mammals have higher or lower body temperatures than humans which suggests that the 36-37 degree C of humans are not a universal gold standard (in mammals).

Probably, for a long time in hominin evolution maintaining the core body temperature was not extremely energy consuming due to tropical conditions. This could have changed during the out-of-Africa migration some 100-60 thousand years ago. Of course this is somewhat difficult assess because early modern humans started to wear protective clothing. In fact, wearing clothes is a most probably adaptive trait to save energy while maintaining core body temperature. Still, it is unclear to me whether physiological adaptations took place as well. Furthermore, there is considerable variation between individuals and also within individuals, the latter in response to environmental conditions and/or behaviour (e.g. exercise), which in principle allows natural selection to change the trait and also shows that slight shifts in body temperature are not harmful individuals.

My question is: Are there significant differences in core body temperature between human populations? Please note that my questions is not why the (average?) human core body temperature has this particular value or why it is different from other mammals or birds.

There is a somewhat related question (also on Skeptics.SE) about lower core body temperature in Japanese people. As far as I know, this difference is rather a measurement thing than a real biological difference, so my question remains unanswered.

$\endgroup$
6
$\begingroup$

Yes there are different physiological temperatures in different ethnicities. To know which temperature range differences are inherited and which are learnt by living in different climates requires surveys of people who are from the same region.

This study states a 0.35 degrees difference between a japanese and a malaysian, 36.95 and 37.3, it's alot. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3929238/

The following study states states a 0.15 degree difference measured with similar precision, https://www.ncbi.nlm.nih.gov/pubmed/20824480

This graph shows that the human body temperature is 36.2 at rest, at night/morning and 37.5 in the middle of the day. : enter image description here http://millar.bio.ed.ac.uk/andrewM/WE%20book99/Part2-examples.html#tth_sEc8.3.4.2

That may account for the 1 degrees difference in Japanese studies, they measure first thing in the morning/ at rest/at night, and japanese body temperature of 0.15-0.35 lower that some other ethnic groups.

There are geographic differences if you test the homeostasis response of different populations, the inner body temperature responses, the temperature of the extremities, sweating responses, the physiological responses and the blood cell characteristics.

Mitochondria has also been shown to be selected by climate type. Populations living in colder environments have lower mitochondrial diversity and that the genetic differentiation between pairs of populations correlates with difference in temperature, and they have found certain genes mutations in the ND3 and ATP6 that seem to be independantly implicated in similar climate adaptations.

The temperature is measured in lots of zones of the body and of the extremeties and the capillary flow. That doesn't account for habituation and acclimatization to tropical or northern climates.

The tropical population was found to have different thirst and sweating efficiency, and to change temperature at different rates to compensate for the same ambient conditions and exercise.

Some schools in China enforce that children run around in shorts in the snow in the winter and at playtime so that they regualte their body in the cold. Some northern people are apparently able to override the unconcsious response of the physiology that can raise body tempereture very effectively, and be able to hold in cold tanks for surprisingly long times.

Cold and hot weather are a strong force on natural selection, as illustrated by mitochondrial adaptations, because an advantageous in temperature regulation brings about a global performance advantage. The physiology of temperature regulation has been subject to many theories and studies, and they have found physiological conditionings can be honed by genetic adaptations in different populations.

Even chimpanzees have similar temperatures:

The cycles of increasing and decreasing body temperature of chimps are exponential and symmetrical, with an amplitude of 2.6-2.9?F (2-3 AM - 2-3 PM) and a 24-hour mean of 99.0?F, or 98.7?F. The S.D. of the 17 daily means was 0.53?F; and of the values at any single hour, 0.63'F....Thus, in the bulk of the species the temperature ranges daily from 37.5- to 39+?C whereas the ordinary range in man is 36.5 to 37.5?C. Low values are similarly reported for several primitive primates.

some references: http://rspb.royalsocietypublishing.org/content/276/1672/3447 https://www.jstor.org/stable/1377087

Actually this study states a 0.35 degrees difference between a japanese and a malaysian, 36.95 and 37.3, and study referenced afterwards states states a 0.15 degree difference,

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3929238/

https://www.ncbi.nlm.nih.gov/pubmed/20824480

$\endgroup$
  • $\begingroup$ That is very interesting! Can you provide references for your claims, though? $\endgroup$ – AlexDeLarge Dec 11 '16 at 17:43
  • $\begingroup$ Hi, it's an interesting quesiton and it gives me a subject upon which to educate myself. I read through 4 papers and 10-20 graphs to get the figures, and saw also a dozen other related research papers. for example rspb.royalsocietypublishing.org/content/276/1672/3447 jstor.org/stable/1377087 ncbi.nlm.nih.gov/pmc/articles/PMC3929238 especially the ncbi page study which answers your quesiton with a high degree of certainty. ill add them to the text. thanks. $\endgroup$ – com.prehensible Dec 11 '16 at 18:05
  • $\begingroup$ Hi, I hadn't seen the above study, which measures a difference of 0.35 between malay and japanese, it's considerable, i had seen the following study from the same researchers states a 0.15 degree difference is similar conditions: ncbi.nlm.nih.gov/pubmed/20824480 $\endgroup$ – com.prehensible Dec 12 '16 at 7:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.