Human body temperature generally decreasing due to unknown reasons

Anthropologists working with the Tsimane people can dig into more details. Researchers can obtain the clinical diagnosis and biomarkers of infection and inflammation for each patient, which means they can test for different factors.

One of the previous mainstream hypotheses was that improved hygiene, clean water, and better medicines reduced the number of infections people experience, thereby lowering their temperature.

Although the inflammation of the Tsimane family is indeed related to higher body temperature, the improvement of hygiene alone is not enough to explain the sharp drop in body temperature.

"For Europe and the United States, it can be explained by the rise of modern medical care and the low rate of lingering mild infections compared with the past." Gurven said, "but, although health conditions have generally improved in the past two decades, infections in rural areas of Bolivia are still widespread."

In the end, the researchers failed to find any single explanation. They said it was probably a combination of multiple factors.

It may be that human living conditions are better today, and our bodies don't have to work so hard to resist infection. It may also be related to easier access to antibiotics, vaccinations or other medical methods.

For more developed communities, it may even be related to modern luxury goods, such as air conditioning or heating, which makes it easier for our bodies to maintain internal temperature.

"Although the body temperature of Tsimane people does change with time and weather patterns, they have not yet used any advanced technology to help regulate body temperature," admitted Thomas Kraft of UCSB Research Anthropology. "However, compared to before the industrial age, there are indeed more opportunities to get clothes and blankets."

We need to conduct more research on various groups of people around the world to figure out what happens to our body temperature and why.

The research was published in "Science Progress".