For generations, we have been taught that the normal human body temperature is 37°C (98.6°F). This standard dates back to the 19th century, when German physician Carl Reinhold August Wunderlich conducted extensive research on body temperature and determined that the average was 37°C. However, recent studies suggest that this number may no longer be accurate. Instead, the average body temperature has been gradually decreasing, raising new questions about human health, environmental factors, and physiological changes over time.
The Origins of the 37°C Standard
In 1868, Carl Wunderlich established 37°C as the average human body temperature after measuring over 25,000 patients’ temperatures in Leipzig, Germany. His findings became widely accepted, and for over a century, medical professionals used this number as the benchmark for determining whether a person had a fever or normal body temperature.
However, in the decades since Wunderlich’s study, medicine and technology have advanced significantly. Scientists now have access to more precise instruments and a larger pool of data across diverse populations. These advancements have led researchers to re-examine the accuracy of the 37°C standard and question whether human body temperature has changed over time.
Modern Research Challenges the 37°C Standard
Several modern studies indicate that the average human body temperature is lower than 37°C. One of the most significant studies on this topic was conducted in Palo Alto, California, where researchers analyzed body temperature readings from three different historical periods. The results showed that the average temperature has steadily declined over the past 150 years.
Key Findings from Recent Studies:
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Palo Alto Study (2020)
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Researchers analyzed over 677,000 temperature measurements from U.S. veterans and historical records.
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The study found that the average body temperature is now 36.4°C (97.5°F)—lower than Wunderlich’s 37°C standard.
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The researchers concluded that body temperature has decreased by 0.03°C per decade since the 19th century.
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UK Study (2017)
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A British study found that 37°C remains a common body temperature, but variations exist.
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Some participants had temperatures as low as 36.6°C (97.9°F), challenging the idea of a fixed standard.
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Bolivia Study – The Tsimane People (2020)
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Researchers studied the Tsimane, an indigenous group in the Bolivian Amazon.
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Their average body temperature has been dropping by 0.05°C per year over the past 16 years.
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The current average among the Tsimane is 36.5°C (97.7°F).
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These findings suggest that human body temperature is not static—it changes over time due to various environmental and physiological factors.
Why Is Body Temperature Decreasing?
Scientists believe that multiple factors contribute to this gradual decline in average body temperature. These factors include:
1. Improved Healthcare and Hygiene
One of the biggest changes since the 19th century is the dramatic improvement in public health, hygiene, and medicine.
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Lower infection rates: In the past, frequent infections caused the body to work harder, raising body temperature. With the introduction of antibiotics, vaccines, and better sanitation, infections have become less common.
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Reduced chronic inflammation: Long-term inflammation was more common in the past due to untreated infections and diseases. Today, modern medicine helps reduce inflammation, leading to lower overall body temperatures.
2. Climate Control and Modern Lifestyles
Technology has significantly changed the way humans regulate body temperature.
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Heating and air conditioning: In the past, people were exposed to extreme temperatures, forcing their bodies to work harder to regulate heat. Today, indoor climate control keeps temperatures stable, reducing the need for the body to generate extra heat.
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Clothing and insulation: People wear better-insulated clothing and use blankets, further reducing the body’s need to produce excess heat.
3. Changes in Metabolism and Nutrition
Metabolism plays a crucial role in regulating body temperature. Some scientists believe that:
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Improved diets: People today have better access to food and improved nutrition, leading to more efficient energy use and less heat production.
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Lower metabolic rates: A decline in metabolic rates over time may be contributing to lower body temperatures.
4. Evolutionary Adaptations
Some scientists propose that this change could be an evolutionary adaptation.
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Over time, the human body may have adjusted to more comfortable living conditions, reducing the need for higher body temperatures.
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This adaptation might be ongoing, meaning that future generations could see even lower average body temperatures.
Does a Lower Body Temperature Affect Health?
While a small decrease in average body temperature may not seem significant, it has important implications for medicine and healthcare.
1. Rethinking Fever and Illness Diagnosis
Doctors have long used 37°C as a baseline to determine if a patient has a fever. However, if normal body temperature is lower than previously thought, then fever thresholds might need to be adjusted.
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Current fever threshold: A temperature above 38°C (100.4°F) is considered a fever.
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New considerations: If normal body temperature is closer to 36.4°C, a fever might actually begin at a lower temperature than currently recognized.
2. Implications for Medical Research
Medical studies often rely on body temperature as a key indicator of health. A shift in average body temperature means that previous studies might need to be re-evaluated.
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Conditions like thyroid disorders, infections, and metabolic diseases could be reassessed based on new temperature baselines.
3. Potential Benefits
Interestingly, a lower body temperature could have some positive effects on health.
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Some studies suggest that a slightly lower body temperature is associated with a longer lifespan.
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Lower temperatures reduce metabolic stress, potentially leading to slower aging and lower risks of age-related diseases.
Is 37°C Still a Useful Standard?
While the 37°C benchmark is deeply ingrained in medical practice, the evidence suggests that it is not an absolute standard for everyone. Instead, body temperature is influenced by:
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Age (younger individuals tend to have higher temperatures)
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Time of day (body temperature is lower in the morning and higher in the evening)
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Activity levels
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Individual differences (some people naturally run hotter or colder)
The idea of a fixed “normal” temperature may soon become outdated. Instead, medical professionals may adopt a more personalized approach, considering individual variations rather than relying on a universal standard.
A Changing Understanding of Normal Body Temperature
The belief that 37°C is the standard body temperature has been widely accepted for over 150 years, but modern research challenges this assumption. Studies from the U.S., UK, and Bolivia suggest that average human body temperature is actually lower today, likely due to improvements in healthcare, hygiene, and lifestyle changes.
This shift in body temperature is not just a minor statistical change—it has significant implications for medical diagnostics, fever thresholds, and our understanding of human physiology. As research continues, we may need to redefine what “normal” means when it comes to body temperature.
While 37°C will likely remain a useful reference point, the medical community is beginning to recognize that temperature is more variable than previously thought. Going forward, doctors and scientists will continue to refine their understanding of human body temperature, adapting to new findings and ensuring that medical standards reflect the most accurate and up-to-date research.
