We’re cooler than we used to be. Literally – human body temperatures have dropped.

The Wall Street Journal reports that since the average human body temperature of 98.7 degrees F was first established, the average human has gotten taller, gained some weight – and lost a little body heat:

The findings have prompted speculation that the pioneering analysis published in 1869 by Carl Reinhold August Wunderlich was flawed.

Or was it?

In a new study, researchers from Stanford University argue that Wunderlich’s number was correct at the time but is no longer accurate because the human body has changed.

Today, they say, the average normal human-body temperature is closer to 97.5 degrees Fahrenheit.

“People are taller, fatter and live longer, and we don’t really understand why all those things have happened,” said Julie Parsonnet, who specializes in infectious diseases at Stanford and is senior author of the paper. “Temperature is linked to all those things. The question is which is driving the others.”

To test their hypothesis that today’s normal body temperature is lower than in the past, Dr. Parsonnet and her research partners analyzed 677,423 temperatures collected from 189,338 individuals over a span of 157 years.

The readings were recorded in the pension records of Civil War veterans from the start of the war through 1940; in the National Health and Nutrition Examination Survey I conducted by the U.S. Centers for Disease Control and Prevention from 1971 through 1974; and in the Stanford Translational Research Integrated Database Environment from 2007 through 2017.

Overall, temperatures of the Civil War veterans were higher than measurements taken in the 1970s, and, in turn, those measurements were higher than those collected in the 2000s.

“Two things impressed me,” Dr. Parsonnet said. “The magnitude of the change and that temperature has continued to decline at the same rate.”