New research challenges the 19th-century body temperature norm

The body temperature of a healthy individual, initially determined in the 19th century, has long been considered to be 98.6 degrees Fahrenheit. Recent research, however, suggests this standard has evolved. We delve into the factors influencing this change and what the current appropriate temperature is.

The globally accepted norm for a healthy person's temperature stems from the work of German doctor Carl Wunderlich in the 19th century, who first set the benchmark at 98.6 degrees, later adjusted to 98.1 degrees.

However, modern studies indicate that these historical standards, while accurate at the time, no longer mirror today's reality. A healthy individual's temperature now averages slightly below 97.9 degrees Fahrenheit.

In 2017, studies in Great Britain supported the 97.9-degree benchmark, yet subsequent research in the United States suggested a further reduction. By 2019, the average body temperature for residents in Palo Alto, California, had dropped to 97.5 degrees Fahrenheit.

This decline isn't only observed in urban settings but also in remote communities like the Tsimane of Bolivia. In this farmer-gatherer tribe, the average temperature has been decreasing rapidly — approximately 0.09 degrees per year, currently resting at 97.7 degrees Fahrenheit.

An interdisciplinary team of doctors and anthropologists, led by Professor Michael Gurven of the University of California in Santa Barbara, examined this trend. They attribute the shift in human body temperature to a myriad of factors best described as scientific and technical progress.

Among the specific causes identified is the improvement in public health due to enhanced hygiene, better access to clean water, vaccines, and advances in medicine. These factors reduce the frequency of infections, thereby decreasing the body's energy expenditure on fighting these infections.

In developed countries, the ubiquity of air conditioning and heating systems further reduces the body's need to regulate temperature manually, contributing to the overall decrease in average body temperature.

The team also considered populations minimally affected by modern science and technology. Even among the Tsimane, who lack access to contemporary medicine and climate control technologies but use blankets and modern clothing, a temperature decrease was noted.

The researchers conclude that no single factor is driving the observed change in body temperature. Instead, it's a combination of improved living conditions that mean the average global citizen now enjoys a better standard of life than counterparts from the 19th century.