THE COOLING BODY

In 1851, the German physician Carl Reinhold August Wunderlich took the temperature of approximately 25,000 people in the city of Leipzig and concluded that the average human body temperature is 37.0°C. Nearly two centuries later, it is still used as the measure by which fevers have been assessed. In a 2017 study of about 35,000 UK adults, the standard temperature was found to be 36.6°C and more recently, researchers from the University of California have shown a further decrease in average body temperature among the Tsimane, an indigenous population of forager-horticulturists in the Bolivian Amazon, sitting at approximately 36.5°C. “In less than two decades, we’re seeing about the same level of decline as that observed in the US over approximately two centuries,” says lead researcher, Professor Michael Gurven. The reason for the decrease in temperature is still unknown. “Declines might be due to the rise of modern healthcare and lower rates of lingering mild infections now as compared with the past,” says Gurven. “But while health has generally improved over the past two decades, infections are still widespread in rural Bolivia. Our results suggest that reduced infection alone can’t explain the observed body temperature declines.”