Map of life expectancy at birth from Global Education Project.

Tuesday, February 12, 2008

Public Health Thoughts for Darwin Day

Understanding evolution is fundamental to the field of public health -- which, as I've said before, is everything. If we teach our children falsehoods, it obviously undermines their prospects to survive and succeed in the world. We aren't just battling for truth, we're battling for survival. Here are just a couple of reasons why the truth really matters.

First and most obviously, we are in a race with the evolution of pathogens, and it's a race we are losing. Heritability works differently in viruses and prokaryotes than it does in the multicellular eukaryotes, but the basic principles of Darwinian evolution apply all the same. HIV evolves to escape antiretroviral drugs and influenza viruses to overcome oseltamivir, bacteria evolve to render our antibiotics useless, and the malaria parasite (a metazoan) evolves to overcome our antimalarial agents. The day may come, and pretty soon, when the revolution in human health and longevity that occurred in the 20th Century is reversed, when we fall helplessly before common infections we thought we had conquered. It won't be any intelligent designer doing that, and praying won't do any good at all.

Understanding evolution is also essential to understanding ourselves. We're astonishingly complex and capable entities, but in many respects, our design is not very intelligent.

The baby's head is too big for the birth canal. Before we had modern obstetric techniques -- forceps and C-sections -- it was all too common for women to die in childbirth. It still is, alas, in some parts of the world.

Our teeth don't fit in our jaws. You wouldn't notice it if you hang out among affluent Americans because all the kids who needed them had extractions and braces -- unfortunately just as they were hitting puberty, which along with the zits was pretty miserable, and you can take it from me. But at least my teeth are straight now.

Our spines and lower extremities have been adapted from quadripedal ancestors, not very well, and we pay the price in disabling low back pain and ubiquitous osteoarthritis in our knees and hips in later years.

What's with that appendix? And the coccyx, whose only function is to cause excruciating pain when we fall on it? There's also that unfortunate problem that in exchange for the power of speech, we lost the mechanism that makes it impossible for the bronchi to be opened when we swallow, and we started choking to death. I remarked before on the years of helpless, vulnerable childhood. Then there's that obesity epidemic -- put a creature that evolved in a condition of chronic calorie shortage in a world of Big Macs and its doom is sealed.

And there's cancer. You can't understand cancer without understanding evolution, which explains the most basic facts about the nature of the metazoans. Same goes for the autoimmune disorders.

All of which is to say, our ills do not afflict us because our ancestors ate an apple, and if that's your preferred explanation, it's utterly useless. Evolution made us what we are, and it's only through the theory of evolution that we can understand ourselves, body and mind. Finally, only by understanding ourselves can we improve our lives.

Ignorance is not bliss. It is death.

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