matt_ridley's picture
Science Writer; Fellow, Royal Society of Literature and the Academy of Medical Sciences; Author,The Evolution of Everything
The Epidemic Of Absence

As Stewart Brand acutely says, most of the things that dominate the news are not really new: love, scandal, crime, and war come round again and again. Only science and invention deliver truly new stuff, like double helixes and search engines. In this respect, the new news from recent science that most intrigues me is that we may have a way to explain why certain diseases are getting worse as we get richer. We are defeating infectious diseases, slowing or managing many diseases of ageing like heart disease and cancer, but we are faced with a growing epidemic of allergy, auto-immunity, and things like autism. Some of it is due to more diagnosis, some of it is no doubt hypochondria, but there does seem to be a real increase in these kinds of problems.

Take hay fever. It is plainly a modern disease, far more common in urban, middle-class people than it used to be in peasants in the past, or still is in subsistence farmers in Africa today. There's really good timeline data on this, chronicling the appearance of allergies as civilization advances, province by province or village by village. And there’s really good evidence that what causes this is the suppression of parasites. You can see this happen in eastern Europe and in Africa in real time: get rid of worms and a few years later children start getting hay fever. Moises Velasquez-Manoff chronicles this in glorious detail in his fine book An Epidemic of Absence.

This makes perfect sense. In the arms race with parasites, immune systems evolved to “expect” to be down-regulated by parasites, so they over-react in their absence. A good balance is reached when parasites try down-regulating the immune system, but it turns rogue when there are no parasites.

And the obvious remedy works: ingest worms and you rid yourself of hay fever. Though it is probably not worth it—worms are no fun.

But how many of our modern diseases are caused by this problem—an impoverished ecology not just of parasites but of commensal and symbiotic micro-organisms too? Do kids today in the rich world have unbalanced gut flora after an upbringing of obsessive hygiene? Probably. How many diseases and disorders are the consequence of this? More than we think, I suspect—multiple sclerosis, obesity, anorexia, perhaps autism even.

There’s a fascinating recent study by Jeffrey Gordon's group at Washington University School of Medicine, St. Louis, showing that if you take the gut flora from an obese person and introduce it into a mouse with no gut flora, the mouse puts on weight faster than does another mouse with gut flora introduced from the obese person's non-obese twin: that's a well designed experiment.

So a big new thing in science is that we are beginning to understand the epidemic of absence.