Darwin's theory 'may explain ill health'

Is obesity linked to evolution?

People become ill because their bodies are unable to cope with the pressures of modern Western life, according to a leading scientist.

Professor Randolph Nesse believes that conditions like heart disease, obesity and drug abuse can all be explained by the fact that the human body was not designed for the 21st Century.

He suggests many serious illnesses occur because the human body has failed to evolve and is still designed for a much simpler existence.

Our bodies are designed for people who used to walk 20 miles each day looking for food and water

Professor Randolph Nesse

Dr Nesse, who is professor of psychiatry at the University of Michigan, is one of the leading proponents of evolutionary or Darwinian medicine.

He uses Darwin's theory of evolution to try to understand human disease and illness.

He says heart disease, obesity and drug abuse are among many diseases and conditions only seen in the West and are caused by "a mismatch" between our bodies and our environments.

Simpler lives

"These conditions are not seen in other parts of the world where people live simpler lives," he says.

"In modern Western hospitals over half of people are there because of a mismatch between their bodies and the environment.

"They have health conditions that never occurred 10,000 years ago when people lived in a more natural environment."

Professor Nesse believes the Western diet is one of the key problems.

Charles Darwin's theory is now being used to examine disease

"Our bodies did not evolve in a modern culture where we can get almost anything we want, when we want and when we do get it tends to kill us," he says.

"Our bodies are designed for people who used to walk 20 miles each day looking for food and water. Diets were high in fibre and low in fat. Nobody was overweight."

However, evolution can also explain why many of us have difficulty following health advice.

According to Professor Nesse, our bodies are designed to like things that are not good for us, from cigarettes to fatty foods.

Similarly, we are not designed to follow advice encouraging us to change the way we live.

Evolutionary medicine also examines why some diseases still exist.

Survival of the fittest?

After all, Darwin's theory points to the survival of the fittest and presumably those who are weak or diseased should have died out.

However, Professor Nesse believes many conditions or symptoms are necessary.

Coughs, fever and diarrhoea are natural ways for the human body to rid itself of toxins.

If they had been eliminated through natural selection then the consequences for the human race could have been dire.

This story is featured in the radio programme Health Matters on the BBC World Service.

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