There has been a change in the healthy temperature of human bodies and the lenient drop in degrees is the new normal.

It has been over two-centuries since we got 98.6 degrees F as the ideal temperature of our body. The German physician Carl Wunderlich set the average body temperature, and anything above or below that would be the cause of disturbance or ailment in the body. However, what struck scientists is, there was a drop in temperature in healthy adults all over the world.

A study conducted in 2017 on 35000 adults in the UK found average body temperature lower than 97.9 degrees and the same research in 2019 done on Americans came down to 97.5 degrees F.

The research caused a stir all over the world. A multinational team consisting of anthropologists, physicians and local researchers operating under Michael Gurven, professor of anthropology at UC Santa Barbara as well as chair of the Integrative Anthropological Sciences Unit, and Thomas Kraft, a postdoctoral researcher working in the same department, has found a similar decrease in temperature among the Tsimane. They are an indigenous population of forager-horticulturists living in the Bolivian Amazon.

In a study spanning 16 years, Gurven, co-director of the Tsimane Health and Life History Project, and his fellow researchers have observed a rapid decline in the population’s average body temperature – a decrease of 0.09°F per year. Presently, their average body temperature stands at 97.7°F. The research has been published in the journal Sciences Advances.

The research is based on a sample of 18,000 observations in which almost 5,500 adults have been monitored. It also accounts for multiple other factors that may affect the human body temperature, such as body mass and ambient temperature.

Earlier, a similar study had been conducted on the US population since the time of the Civil War. However, the reason for the declining temperature could not be explained. Gurven thinks that something about human physiology may have changed. One popular hypothesis is that humans have contracted fewer infections over time because of clean water, improved hygiene, vaccinations and advanced medical treatment.

The question is, then, why have the body temperatures declined over time for both the Americans and Tsimane? It could be because people are in a better condition overall, or have easier access to antibiotics and other treatments. It is also possible that anti-inflammatory drugs such as ibuprofen may play a role. However, no theory can explain the decline definitely.