In ancient times, people thought illnesses were caused by bad odors, demon spirits and perhaps even retribution for our sins. Now we are discovering that evolution may be to blame.
Thousands of years ago, Greeks believed that if a man had a fever there was too much blood in his system. Their cure was to cause him to bleed until he recovered.
Up until just a few hundred years ago, doctors followed a similar practice, using leeches to draw out “bad blood” so that the body could produce a supply of “clean blood” to replace it.
Then, in the mid-1800s, Louis Pasteur came along and proved that cholera is actually caused by microscopic germs. His groundbreaking work extended to diphtheria, anthrax, scarlet fever and rabies, opening the way for new fields in microbiology and immunology.
Since then, science has developed new ways to explain and treat diseases. However, germ theory and modern medicine could only explain the mechanism of disease and healing—the “how” not the “why”—until Charles Darwin introduced the theory of evolution.
It is only now becoming clear through the new field of evolutionary medicine that health and disease correlate to natural selection and adaptive changes that occurred in the distant past.
For example, we know that the body develops a fever when experiencing the flu and it is not the result of “too much blood.” Scientists now believe that we have our lizard ancestors to blame for this inconvenience.
According to recent research, infected “cold blooded” lizards would move to warmer places in an attempt to increase body temperature and fight illness. This may explain how elevated body temperatures evolved in humans as a way of fighting and destroying pathogens when catching the flu.
Moreover, studies suggest that when we take medications to reduce the fever, we are actually intervening with our body’s natural way of fighting infection, thereby prolonging the process of recovery.
Through natural selection, traits endure because they maximize a life form’s ability to survive. Take, for example, the antibiotic resistance of a pathogen like tuberculosis. TB germs less affected by antibiotics survived and passed on their superior traits, creating generations upon which the drugs have no effect.
There is no doubt that evolutionary medicine has given us an historical basis for explaining the existence of disease in humans. It has helped to shift the focus of contemporary medicine to why diseases develop and not just how. This will in turn aid in the production of improved medications and preventive measures to effectively target disease and pathogens in century ahead.
In the concluding pages of Darwin’s book “Origin of Species,” he predicted that his work would lead to more important research in the future. It certainly seems that he was right and his vision is being fulfilled, as evolutionary medicine helps unlock the mysteries behind today’s most baffling diseases.
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