The author is a physician known for his previous tissues and organs and causing its death. The book starts with a short, friendly in the Four Corner States of New Mexico, the author introduction where the author confesses his admiration of shows that viruses are more than parasites. In this context, Jacques Monod though recognizing that his viewpoint was Ryan had a chance to interview Terry Yates, Professor of exclusively reductionist and selectionist. Monod believed Mammals at the University of New Mexico, who demon- that mutation was the main source of genetic change.

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Sep 08, Dennis Littrell rated it it was amazing The starling and scary role played by viruses in biological evolution 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 suggesting the word "revolution. 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. Survival of the fittest may include carrying around lethal viruses that can wipe out your ecological competition. 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.

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 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. 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.


The Visitors That Came to Stay

Overview The extraordinary role of viruses in evolution and how this is revolutionising biology and medicine. His explanation of the role of natural selection in driving the evolution of life on earth depended on steady variation of living things over time — but he was unable to explain how this variation occurred. In the years since publication of the Origin of Species, we have discovered three main sources for this variation — mutation, hybridisation and epigenetics. Then on Sunday, 12th February, the evidence for perhaps the most extraordinary cause of variation was simultaneously released by two organisations — the code for the entire human genome. Not only was the human genome unbelievably simple it is only ten times more complicated than a bacteria , but embedded in the code were large fragments that were derived from viruses — fragments that were vital to evolution of all organisms and the evidence for a fourth and vital source of variation — viruses.


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The book presents astrobiology both as a developing science and as the science of the future. The origins of life and the possibility of life elsewhere continues to be a subject of scientific and philosophical examination. These topics evolve with time as our understanding of life itself and the laws of chemical and biological evolution evolve. Astrobiology: An Evolutionary Approach aims both to provide a foundation in astrobiology and to describe the most challenging questions and problems in the field.




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