What Viruses Might Do for a Living

Imagine, if you will, a committee of our brightest biochemists meeting in the late 1960s trying to make guesses about what might be happening next in the field of molecular biology. If they'd stayed up all night for weeks at a time, it is highly improbable that anyone could have guessed that recombinant DNA would happen next, or that this research technology would soon become the most important advance in biological science of the 20th century, much less that we would be purifying and scrutinizing at first hand any gene of interest in the whole biosphere by simply inserting it into an appropriate vehicle or attaching it to one virus or another and growing genes of our choice in vat-sized batches. It's already commonplace to hear that the next great surge in biomedical science, already well underway, will be in the field of neurobiology, and I agree with this one. I have no trouble at all in accepting the prediction that the events ahead in our comprehension of the human brain, including those strangest of all natural phenomena—human consciousness, awareness and language— are going to sweep us off our feet someday. The trouble with saying things like this is that when the astonishments do begin coming in, some will be heard to say "Ah, yes, that's exactly the kind of thing I knew was going to happen. No surprise at all; my group told you so." But maybe we should each be allowed just one prediction, and not one so general in nature. Something more specific and explicit than, say, the prediction that human consciousness will someday come into view. Well, I'd be glad to try one of mine. The field I have the highest hopes for in the decades ahead is virology, plain old virology. But for a special reason. Why Do Viruses Exist? Viruses first came into view as pathogens, and for most of the years that we've known about them they've been regarded as a biological problem of interest to science primarily because they cause disease. But the field has been set in a totally new kind of motion by recent events in molecular genetics. So I'd be willing to predict this based on the known existence of numerous viruses for which no biological function can be assigned (that is to say, no known disease state exists). Why are so many viruses being passed around among every class of living creatures on the planet, including human beings, and such a short list of bona fide diseases? Why do the things exist? Maybe they are there in aid of evolution. It's already a sure thing that in the world of bacteria, arguably the dominant form of life in the biosphere, at least on this kind of planet, the viruses and their near neighbors the small replicons are continually being passed around as though at an enormous party. They carry novel bits of genetic in-formation from one bacterial cell to another across species lines and provide genetic strategies to be used in whatever contingencies may turn up by natural selection. Maybe instead, the existence of viruses will turn out to be, the way great stretches of time can ultimately be bypassed in the origin of species, providing an explanation for the gaps in the record of paleobiology and thus allowing for the phenomenon of saltation in evolution. Maybe to get all the way from the earliest bacteria to the human brain in so remarkably short a time as 3 ½ odd billion years you need more ways than sex allows for the exchange of genetic ideas. We already know that plants can engage in recombinant DNA with their resident bacteria, as happens in crown gall, where the plant receives genetic instructions directly from the bacteria's DNA. If viruses can do this kind of thing for a multicellular, eukaryotic organism like us, then the importance of the rapid spread of viruses around the Earth might not be for the spread of disease, as in the 1918 influenza pandemic. Maybe that was an anomalous event, a biological accident, something dropped by nature—viruses doing something feckless and harmful on a huge scale and maybe that is what viruses do for their living. Well, if something like that ever turns out to be true, I'm going to be immensely surprised, but I won't say so. Instead, I'll reach back into my academic background and say "But of course. I told you so." All you needed to make the sudden jump from nonhuman primates to Homo sapiens were short strings of DNA tugged along by a virus, inserted at just the right site in the prehuman genome and carrying this simple instruction: "Don't switch off the replication of those columnar modules of neurons in the cortex. Keep making them and don't stop. And when you've made enough of them, you'll have consciousness, and then language. But don't stop there, keep making more of them. Heaven knows how it will turn out, but it will be something new." So the next time you feel a cold coming on, remember that you may be giving evolution a tiny boost. Thomas is president emeritus of the Memorial Sloan-Kettering Cancer Institute, 1275 York Ave., New York, NY 10021, and the author of numerous popular books on science. This article is adapted from the First Annual Mahlon Hoagland Distinguished Lecture "On Progress in Biology, " given at the Worcester Foundation for Experimental Biology, Shrewsbury, MA 01545, on October 3, 1986.

What Viruses Might Do for a Living

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