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Health, psychology & science stories

 

Darwinian Medicine, and its founders Nesse and Williams

17 July 2002

Published in The Age


Recent decades have seen the birth of innumerable new sciences. Many of them - such as paleolithic diet, evolutionary psychology and Richard Dawkins’s startling insights into the primacy of the gene - have sprung from the rich soil laid down by Charles Darwin 142 years ago.

In writing The Origin of Species, Darwin did not merely change thinking about science and religion. He laid down a paradigm which thinkers have worked within ever since. The brand new science of Darwinian Medicine is the latest in a long line of examples.

A bit like the God of the Old Testament, evolution cares a lot more that we go forth and multiply than it does for our comfort, or even our happiness. Darwinian Medicine is now applying that difficult lesson to the understanding of disease.

Appropriately to this democratic era, its bible is not some vast technical tome, but a book of 290 pages which is now selling well in paperback in bookshops from China to Europe.

In 1995 Randolph Nesse (a psychiatrist) and George Williams (an evolutionary biologist) published their seminal book Why We Get Sick: The New Science of Darwinian Medicine.

The work was so understated, yet well-sourced and common sensical, that it jumped the “international controversy” phase which most new sciences go through, to become hailed as a breakthrough in the understanding of illness. (“Buy two copies, and give one to your doctor,” wrote Richard Dawkins.)

Randolph Nesse is now both Professor of Psychiatry and Professor of Psychology at the University of Michigan. He told The Age that the book “continues to sell well. It is used in courses all over, for anthropology, nursing, biology and medicine. It is selling especially well in Germany, but is also available in China, Japan, Taiwan, Italy, Portugal, Korea”.

Essentially, Nesse and Williams believe a knowledge of evolution will enable us to better understand why an illness arises (thus aiding prevention), how to cure it more quickly, and in some cases when to leave it alone.

Nesse and Williams point out that we humans were “designed” to be hunter-gatherers, and that today’s fatty diets, drugs, sedentary lifestyles, artificial lights and central heating make a novel environment for us.

“From this mismatch between our design and our environment”, they write, “arises much, perhaps most, preventable modern disease”.

For example excess consumption of salt, saturated fats and sugars is undoubtedly playing havoc with bodies blueprinted in  environments where these things were scarce. And myopia arises from early “close-work” such as childhood reading.

Darwinian Medicine also points out that, regardless of environment, some illness is made more likely simply by evolution’s “design compromises”.

For instance “walking upright gives us the ability to carry food and babies, but it predisposes us to back problems,” the authors write.

Related to this are “evolutionary legacies” - design features such as a windpipe situated perilously close to a “food-pipe” - brought about because evolution cannot easily go backwards to undo earlier design.

The authors also look at some genes which, they say, can both provide benefits and cause illness. The gene which causes sickle cell anaemia, for instance, also prevents malaria. Again, the lesson is that Nature isn’t perfect, but reaches the best compromise available.

Another element of the Darwinian Medicine synthesis relates to infection - and the eternal parasite-host contest. Nesse and Williams point out that knowing the various strategies employed by pathogens such as viruses and bacteria to invade, evade, poison, trick, incapacitate, disguise, mimic, manipulate, hide, shape-shift, mutate, multiply and disperse (within) our cells and bodies - and the various strategies employed by our bodies to prevent, defend, puncture, surround, bind to, expel and repair in the wake of the pathogens - should give doctors a far clearer idea of whether a symptom is designed to benefit ourselves or the pathogen.

Thus it may sometimes be helpful to medically attack a sneeze which benefits a pathogen (by dispersing it), but unhelpful to attack a fever which benefits its human host (by reducing infection).

Indeed Darwinian Medicine proponents believe that suppressing fever - or any other defence we’ve evolved against infection, such as cough, running nose or diahorreah - can sometimes risk impeding the body from fighting the invading pathogen. Fever  raises the body’s temperature to make it less hospitable to bacterial reproduction, and increases functions such as the white blood cell production of the immune system.

Nesse and Williams also raise the alarm in regard to the practice of dosing farm animals with antibiotics, which is encouraging human pathogens to build up antibiotic resistance. By eating poultry, dairy and meat produce - unless it’s certified organic of course - we risk turning our bodies into evolutionary laboratories which are “selecting” for antibiotic-resistant strains of microbes.

Professor Nesse told The Age: “This is a major public health issue that was the topic of an editorial in Science a few months ago.”

In 1999 Australia imported about 700 tons of antibiotics - two-thirds of them for veterinary use. A better understanding of the Darwinian contest between parasites and hosts within the egg, dairy and meat industries (to say nothing of better-developed consciences) could have prevented this practice.

Nesse and Williams argue that doctors, too, should be analysing this eternal parasite-host arms race - for the benefit of patients:

“Instead of just relieving symptoms and trying, perhaps ineffectively, to kill the pathogen, we can analyse its strategies, try to oppose each of them, and try to assist the host in its efforts to overcome the pathogen and repair the damage.”

In essence, Darwinian Medicine tries to give practitioners and patients more options, by asking why instead of how.

Is Darwinian Medicine catching on? Professor Nesse said: “I did a survey of all deans of medical schools in North America and will soon write up the results. Mostly I found that they don’t teach evolution at all, and don't even know many of the basic concepts.”

Associate Professor Susan Elliott, who oversees the development of Melbourne University’s Medicine curriculum, is more sanguine:

“I think there are areas where Darwinian principles are coming through. For example, in paediatrics in recent times I’ve read that you don’t treat fevers unless they’re very high, and you’re concerned about a risk of fitting - for the very reason that fever is an adaptive thing. Similarly, as a gastro-enterologist I teach my students that you don’t give anti-diahorreah therapy to children, and often not to adults either - unless it’s incapacitating of course - because diahorreah is a natural response to get rid of the bug.”

It’s worth noting that holistic healers have been teaching these courses of action for many decades: though Nesse and Williams are at pains to distinguish Darwinian Medicine from holistic medicine.

Randolph Nesse says his research “is now focused on the evolutionary functions of low mood and depression”. He has also created “a new course on Darwinian medicine, which begins in January” at the University of Michigan.

As for the future of the science he co-fathered:

“There is growing acceptance, but because medical schools don't even have evolutionary biologists on their faculties, there is no-one to let them know what they are missing. Eventually today's students will be in charge, and they will change things.”


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