“The average human body temperature is exactly 98.6°F (37°C).”

The idea that 98.6°F (37°C) is the definitive normal human body temperature has been a widely held belief for over a century. This precise figure originated from the extensive work of German physician Carl Wunderlich in 1868. He meticulously collected millions of temperature readings from tens of thousands of patients, establishing 98.6°F as the statistical average of his findings. This benchmark quickly became ingrained in medical practice and public understanding.

However, modern research, including significant studies by Dr. Julie Parsonnet and her team at Stanford University, has challenged this long-standing standard. While Wunderlich's work was groundbreaking for its era, his measurements were taken when chronic infections and inflammation were more prevalent. Today, studies suggest the average human body temperature is closer to 97.9°F (36.6°C). This updated understanding reflects improvements in public health and a general decline in inflammation over the past two centuries.

The persistence of 98.6°F as the "normal" temperature stems from its early and widespread adoption in medical textbooks and popular culture, offering a simple, memorable number for health reference. Yet, the reality is that a healthy body temperature is far more dynamic and personal. It naturally fluctuates throughout the day, influenced by factors such as age, sex, activity level, and the time of day. Therefore, while an average exists, an individual's "normal" temperature is a range, not a single, fixed point.