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In the nearly two centuries since German physician Carl Wunderlich established 98.6°F (37 C) as the standard "normal" body temperature, it has been used by parents and doctors alike as the measure by which fevers—and often the severity of illness—have been assessed.
Over time, however, and in more recent years, lower body temperatures have been widely reported in healthy adults. A 2017 study among 35,000 adults in the United Kingdom found average body temperature to be lower (97.9°F / 36.6 C), and a 2019 study showed that the normal body temperature in Americans (those in Palo Alto, California, anyway) is about 97.5°F (36.4 C).
A multinational team of physicians, anthropologists and local researchers led by Michael Gurven, UC Santa Barbara professor of anthropology and chair of the campus's Integrative Anthropological Sciences Unit, and Thomas Kraft, a postdoctoral researcher in the same department, have found a similar decrease among the Tsimane, an indigenous population of forager-horticulturists in the Bolivian Amazon. In the 16 years since Gurven, co-director of the Tsimane Health and Life History Project, and fellow researchers have been studying the population, they have observed a rapid decline in average body temperature—0.09°F per year, such that today Tsimane body temperatures are roughly 97.7°F (36.5 C).
"In less than two decades we're seeing about the same level of decline as that observed in the U.S. over approximately two centuries," said Gurven. Their analysis is based on a large sample of 18,000 observations of almost 5,500 adults, and adjust for multiple other factors that might affect body temperature, such as ambient temperature and body mass.
The anthropologists' research appears in the journal Sciences Advances.
Journal Reference:
Michael Gurven, Thomas S. Kraft, Sarah Alami, et al. Rapidly declining body temperature in a tropical human population [open], Science Advances (DOI: 10.1126/sciadv.abc6599)
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @09:20PM (2 children)
Also CO2 is heavier than oxygen so it will tend to sink down displacing oxygen. It's not like gasses in the atmosphere are evenly distributed. Lighter gasses tend to move up relative to heavier ones. More CO2 lower down = less oxygen lower down as the heavier gas will displace it.
CO2 is also more soluble in water than oxygen.
Unfortunately when trying to do a Google search on changes in O2 concentrations over the years there is little information on the altitude of the measurements.
Reduced O2 concentrations could also be a bigger problem for enclosed regions where a lot of oxygen is being burned up and the CO2 has no place to easily escape and may sink relative to oxygen.
Overall I think you seem to have a point but I'm just trying to be thorough.
Thanks for your thoughts as well.
(Score: 0) by Anonymous Coward on Sunday November 01 2020, @09:42PM
It should also be considered that it's not like CO2 concentrations are evenly distributed across the globe either. CO2 concentrations may tend to be higher where human activity is more prevalent and this may result in reduced O2 concentrations in those areas since the CO2 may sink relative to the O2 when it first gets expelled from the sources that consume O2. So CO2 and O2 concentrations are neither evenly distributed vertically or across the globe so if we are consuming more O2 then we might be exposed to lower O2 concentrations.
So the studies intended to measure overall O2 concentrations and that notice only a slight difference because they try to filter out the noise overall may not be that relevant as the noise is what matters in these situations since the noise is where humans tend to live the most.
(Score: 1) by khallow on Monday November 02 2020, @04:28AM
The atmosphere is pretty well mixed up to the transition to the stratosphere. There's not enough CO2 to allow for such stratification with Earth weather to mix things up.