There will be many tributes to sci-fi writer Greg Bear, but I would like to offer something somewhat different in appreciation.
Whenever someone asks me what kind of sci-fi I most enjoy, I inevitably start by mentioning Greg Bear as an example. He wrote what is called “hard sci-fi,” meaning that its hallmark is being scientifically plausible. But in one instance, Bear went beyond even that and arguably contributed to science itself with this book Darwin’s Radio (1999). I hope to explain that contribution here in tribute to Bear, who recently died in a complication following heart surgery.
I’ll begin by asking Bear’s question. Do viruses contribute to (some people might say “cause”) evolution?
Until the 1990’s, the answer was invariably an emphatic “no.” That notion was thought to be contrary to Darwinism. But by a decade later, every Intro to Biology textbook (for majors) was saying, “Of course viruses do.” What changed?
Bear was part of that transformation with this sci-fi book, and that is what I will discuss here. The following will be my own understanding of this change, not Bear’s, but Bear certainly contributed to the science by connecting the dots, so to speak, of what was already known. He challenged biologists to tell him why he was wrong in answering “yes,” and he joined with them in conferences that popularized the very question. Certainly, he was what led me personally to an interest in this question, as well as to some other related ideas that follow from it.
contrary to Darwin?
First of all, why was it considered contrary to Darwin?
Darwinism works via gradualism, but viruses can in theory bring about change that is relatively sudden. In Darwinism, evolution works via “descent through the generations,” meaning that each offspring has a minor change but these small changes accumulate so that after many generations they make an overall evolutionary novelty. But viruses, by infecting many hosts, can in theory spread a change, not just to offspring, but to many individuals of the same generation—and all in roughly the same timeframe. The fancy way of putting it is that Darwinism works via vertical transmission (from generation to generation), while viruses would entail horizontal transmission (the change being passed among members of the same generation).
So to a strict Darwinist, we couldn’t have that, not horizontal transmission. And the Darwinists were already a pretty testy lot about gradualism. That was because the Harvard paleontologist and best-selling author Stephen Jay Gould had argued that the evidence from the fossil record was that new species seemed to spring up fully-formed and all-at-once and then later suddenly go extinct, not gradually come into being and then gradually change into something else. The proposed intermediary transitional creatures expected by Darwinism did not exist in the fossil record, according to Gould. His theory of the sudden appearance of new species was called “saltation,” and the strict Darwinists were pretty sure that that had to be wrong. Saltation (which in theory viruses could bring about as they infected many individuals simultaneously) could not exist, at least if evolution worked via Darwinism.
So, what changed in the thinking of biologists starting in the 1990’s?
There were several new developments which changed biologists’ thinking, mostly related to the new ability to read the specific contents of genomes. In other words, molecular biology started weighing in on the arguments previously made by naturalists.
Among these developments were the following:
It became known that some viruses could incorporate themselves into a host’s own genes (since a virus was basically a piece of DNA or RNA that was covered by a protein, and then the protein disintegrated after the virus entered a host cell, leaving the viral DNA to float around in the cell and possibly join the host genes). Further, it was learned that, as the virus left one host’s genes and went to another host’s, it could break off a piece of the first host’s genes and bring it to be included in the new host’s genes. It was hard not to conclude that the viruses are accomplishing horizontal transmission.
Also, it was discovered that many viruses are capable of “hypermutation,” meaning that they can change their genetic makeup every year. Some even have parts of them with the job of mutating their other parts. So that is a source of non-gradual genetic change.
And it became clear that viruses tend to evolve in the direction of becoming less lethal to their hosts. That makes sense if we consider two sets of random genetic changes, one set being more lethal and the other less so. The lethal changes will kill the host before the host can walk around spreading the virus, so there won’t be more of them in the long term. But the non-lethal changes will let the host spread the virus and so help this non-lethal version to predominate. The most successful viruses don’t make their hosts sick at all, so they can become incorporated into the host’s genes without setting off a major host defense. They just sit there among the host’s genes.
And if such viruses get into the reproductive system, then some of them can even be inherited and passed on to offspring. So at what point is such a virus not part of the host’s own genes?
And then there is how finding viruses in our genes reveals a wicked evolutionary history of the hosts using viruses to do battle with other species. If two different but related species, especially primates, are competing for the same food to the point of starvation, it turns out that one species will release its virus (that has been sitting dormant in its genes) to go kill the competitor, leaving the food for the first species releasing the virus. The virus will kill many but not all of the second species, and then its survivors will have this same virus dormant in them to go kill a third species in a later encounter.
Yes, we, the living, are all the evolved end-products of this wicked process.
In addition, Carl Woese, the father of the study of archaebacteria, showed how these first and most primitive bacteria evolved via horizontal transmission, not vertical transmission as in Darwinism. (But they wouldn’t give Woese a Nobel). Yet it was also learned that mitochondria (the “batteries” of advanced cells) historically became part of the advanced cells when one lesser organism ate a still lesser organism, but instead of being digested, the engulfed cell became the mitochondria of the larger cell—which was not a gradual process of descent.
But what really changed most biologists’ minds was the argument that all of that still didn’t undermine Darwinism, after all. Darwinism predicts that evolution occurs in a two-step process wherein first there is a minor change, brought about by cosmic radiation or by copying errors as the cells divide, and then in step two only those changes which better adapt the organism to the environment survive in a battle of the fittest. But viral infection can be understood as belonging only to step one (about how the genetic changes happen), leaving intact most of the part about the survival of the fittest. Only those viral changes which help the organism survive are going to end up in a novelty.
The Darwinists could relax and accept viral contributions to evolution. It was just a matter of adding viruses to the list of what could create mutations, along with cosmic rays and copying errors.
Still, the viruses also could bring about horizontal transmission, and that meant that evolution could be “speeded up” via viruses spreading genetic changes. The spreading of genetic change did not have to go through the slow process of dissent through the generations. And that was Bear’s point, for his sci-fi stories. Viruses could speed up evolution.
What Bear did was to challenge biologists in face-to-face meetings to admit that all of the above could add up to viruses contributing to evolution—viruses could make for sudden evolution rather than gradualism—and many biologists then did agree with him.
And once we understand the interplay of viruses and evolution, it becomes possible to fathom other applications, as well. Since these were not a part of Bear’s agenda, I will only mention one example here. But these further issues follow naturally from asking Bear’s question.
One such application is gene therapy. How does it work?
Today, it isn’t yet entirely successful—we can think of it as still in development—but consider how the inherited disease sickle cell anemia is the result of a defective gene for making red blood cells. The hope is to replace the defective gene with a normal one. But how do we get the good gene into the patient’s cells?
Gene therapy consists of attaching the normal gene to a virus capable of entering the cell and also capable of joining with the host genes, thereby adding the normal gene to the host’s.
A lot more could be said, but my point here is just to illustrate some of the greater implications of Bear’s question.
And that brings me to one final observation. Bear is showing us yet again an example of how science changes its mind.