Human Body Temperature Cools: Scientific American

Health officials and the public have long assumed that normal body temperature was a narrow range around 37 degrees Celsius, or 98.6 degrees Fahrenheit. In 1851, a German doctor tested 15,000 patients and determined the average. New studies reviewed historical data and suggest that temperatures declined, putting the average at 97.5 degrees Fahrenheit, or 36.3 degrees Celsius. Researchers suggest the temperature decline could be related to surroundings and indoor-temperature controls, clothing styles, increased height and weight, changes in work and exercise habits, and even a decline in infectious diseases. One author theorized that it might be healthier to have a lower metabolism and body temperature. Critics suggest the methods for collecting temperatures may not have been consistent in the historical data sets; also, temperature can vary on activity or time of day. – YaleGlobal