Arno Karlen died a year ago this past May. Too bad. I’d like to ask him about beef’s food safety efforts. I wonder if he would think that we will ever get food clean enough to prevent food poisoning.
I don’t think we will. I don’t think it’s possible.
I think Karlen’s 1995 book Man and Microbes: Disease and Plagues in History and Modern Times should be required reading in American high schools. It recognizes that humans and disease-causing organisms have evolved (and continue to evolve) together. As our forebears changed their habits—developed agriculture, moved to crowded cities and opened new lands and trade routes—they continually ran into new disease pathogens.
It was always nasty. Lots of short lives and dead babies. Until science came along.
The book cites an estimate by researchers that interaction with dogs, cattle, sheep, goats, pigs, horses and poultry introduced more than 250 new zoonotic pathogens. "Agriculture brought
humans so many new pathogens that it seems wondrous they survived," Karlen wrote.
Many—sometimes millions—died with each new exposure and each new plague, but everything that didn’t kill the survivors made them stronger. They developed immunities to these pathogens. The epidemics that decimated the New World populations when Europeans arrived were just a fast-forward version of the history of the Old World.
Until the advent of modern science, we were forced to submit to nature’s rules through a cruel system of survival of the fittest. Mother Nature is a bad mother when she wants to be.
So thank science and technology for a more humane system. We’ve learned that certain hygiene practices—things like sewers, rat traps and washing our filthy hands—help. We’ve got antibiotics and vaccines that simulate exposure and resistance without all the suffering that nature requires.
Exceptions to the rule. Karlen pointed out that most of the diseases that afflicted us historically were rooted in filth. Polio was different.
Nobody knows when it started, but polio wasn’t much of a problem until people learned to clean up. Even during the height of the epidemic in the 20th century, polio was virtually unknown in less developed countries. That confused researchers until they found that the virus was common in human populations. It’s just that most people were immune, because their lifestyles had challenged their immune systems early.
"The virus, once ubiquitous and silent, became a problem in advanced nations when poverty and dirt dwindled," Karlen wrote. "Researchers found that in warm, crowded cities such as Cairo and Bombay, most children were exposed to the polio virus and immune to further attack by age 3; paralysis and death were rare. This must have been true in the crowded, unhygienic cities of the West until the late 19th century."
Which brings us to the late 20th and early 21st centuries and asthma. It is an increasing problem in the U.S., but—like polio a century ago—not in the developing world. According to one school of thought, the explanation might be that kids today live in such a clean world that their immune systems don’t develop right.
- September 2011