A major thesis of this amazing book is that plants and animals including most significantly humans co-evolve with viruses. The term "virolution," presumably coined by Dr. Ryan, who is both a physician and an evolutionary biologist, comes from the words "virus" and "evolution" but also suggests the word "revolution." The idea is that instead of being merely agents of pathology, viruses can also work together with their host to help it survive. Ryan gives the example of grey squirrels imported from America invading the territory of red squirrels in Britain. He writes:
"At first naturalists assumed that the grey squirrel was winning the survival battle because it was larger and more aggressive than the native counterpart, but now we know that the grey squirrel is carrying a squirrel pox virus that causes no disease symptoms in its symbiotic partner but appears to be lethal to the red squirrel." (p. 96)
In other words what we have here is war by an organism's own viral pathogens! Survival of the fittest may include carrying around lethal viruses that can wipe out your ecological competition. Ryan notes "We believe that HIV-1, the main virus of AIDS, was transferred to people from a specific group of chimpanzees. We also know that, in chimpanzees, HIV-1 grows freely and reproduces in their internal organs and tissues, but it causes no evidence of disease." (p. 86)
So what apparently happened is some bush meat eaters shot some chimps, ate and/or sold the meat and humans got the virus. Revenge of the dead chimp! Well, perhaps. But look at it this way. Imagine humans in prehistory or even humans a few centuries ago in the Congo jungle looking to take over some chimp territory. After some close contact, the virus jumps from the chimps to humans and the humans die. Survival of the fittest!
Ryan refers to this as an example of "aggressive symbiosis," and this is how it works in general: two similar species occupying similar ecological niches come into contact. Which is to prevail? One carries a virus like a loaded gun in its tissues. The virus jumps to the other species and typically is extraordinarily virulent and kills them. Or perhaps there is a dueling of viruses, one from each species. At some point the only survivors are those with immunity to the viruses.
Ryan makes a further point with this example (quoting Max Essex on the deliberate use of a myxomatosis virus to kill rabbits in Australia): "The...virus killed...some 99.8% of the rabbits. But then two things happened. Number one - within four years, the resistant minority grew so you had a different population of disease-resistant rabbits... And number two - the myxomatosis virus that remained [as a persistent infection in the rabbits] was less virulent, so I think there is crystal-clear evidence that both the host and the virus attenuated themselves for optimal survival in that situation." Furthermore (and this brings us back to the previous point), any new rabbits brought in would be at a disadvantage because they would have no immunity to the virus and the surviving rabbits would. (pp. 87-88)
In other words looked at from an evolutionary perspective, host and virus worked together in a mutualistic symbiosis. In my mind this raises the question, what really did happen to the Neanderthal? We do know what happened to the natives of the Americas when they came into contact with the smallpox virus carried by the Europeans. Could a virus from homo sapiens have wiped out the Neanderthal, or at least helped humans become the sole hominid survivors?
In the largest sense, this idea of host and virus working together would seem to be more powerful than any kind of sharp tooth and massive claw in the struggle for survival. The old idea of survival of the fittest must now be seen in a different light. I have said for many years that "everything works toward an ecology" and "everything works toward a symbiosis," meaning that in a typical environment, if one species is able to work together with another, they may enjoy an advantage over rivals. Consequently, those species that are able to form symbiotic relationships are the ones more likely to survive. What this means for evolutionary theory, as Dr. Ryan has pointed out, is that symbiosis is a much more important part of evolutionary biology than has previously been thought. My guess is that the revolution begun by Lynn Margulis, who first saw the eukaryotic cell as a mutualistic development from parasitic relationships, will be accelerated by the work of Ryan and others to the point where the prevailing view from evolutionists will be that it is cooperation rather than competition that most characterizes fitness.
And that is what makes this book so important. It signals a great shift in our understanding of how evolution works.
But that is not all. Ryan shows that the so-called "junk DNA" in genomes is anything but. Much of it is viral ("endogenous retroviruses") and it is there as evidence that humans and pre-humans went through many periods of aggressive symbiosis including the horrid plague stage. We now see that plagues, from an evolutionary perspective, are common and part of how the evolutionary process formed us. Furthermore Ryan writes about how viral genes can help with the development of the embryo in the womb. In other words, viral DNA in part directs the protein building that makes for human beings, and indeed for many forms of life.
In the latter parts of the book Ryan explores the role of viruses in autoimmune diseases and cancer. He also considers the role of hybridization in evolutionary change and that of epigenetics. Particularly interesting is the work of Eva Jablonka and Marion J. Lamb that suggests that "new species might arise through the inheritance of acquired epigenetic changes," causing Ryan to remark, "they were resurrecting the long-discredited spectre of Lamarckian evolution." (p. 312)
The book is dense, difficult and perhaps revolutionary in scope.
(Note: this review and many others can be found in my book, "Understanding Evolution and Ourselves," reviews by Dennis Littrell now available on Amazon.)
Understanding Evolution and Ourselves