What Frank Ryan demonstrates in this book is that evolution by symbiosis has been a "blind spot" for evolutionists since the time of Darwin, and even today is greatly underestimated by the Darwinian establishment as a force in evolutionary change, especially in speciation.
Ryan, who is an expert on viruses having penned such well-received books as Virus X: Tracking the New Killer Plagues and The Forgotten Plague, begins with some interesting history from Darwin's time showing that Darwin did not (and could not, to be fair) appreciate the role symbiosis plays in evolution. Indeed Ryan demonstrates that the process of symbiosis, and its sister processes, parasitism, mutualism and disease, itself has been misunderstood. A relationship between species may begin as parasitism (or disease) and eventually evolve into a symbiosis. This experience between species has been going on since before there were multi-cellular organisms, and is a feature of every species in existence. All species interact with some other species in symbiosis.
This central realization of the book leads to something like a new way of looking at evolution. Natural selection is still a factor, but not necessarily the major factor anymore. This is implied in the discovery not too many years ago that the mitochondria that inhabit the cells in our body are almost certainly the remnants of a once free-living bacterium that, long ago in the primeval soup or near an undersea volcanic caldron, entered a cell and stayed. We are then the product of symbiosis, which may have begun as one cell invading the other, and over the eons turned into a domestic living arrangement with the invading cell providing power to the larger cell as that cell protects and feeds the symbiont that is now earning its keep.
How eye opening this conception is! Imagine the planet filled with life forms that are composed of a dozen, or perhaps hundreds of similar arrangements made over the eons. This is evolution not by gradual steps but evolution by saltation, with a new species arising almost (geologically speaking) immediately. Such a conception would explain many of the gaps in the fossil record.
Ryan builds a strong case. Along the way he looks favorably upon James Lovelock's Gaia hypothesis (one of my favorite modern ideas) and explores the role that viruses have had in gene transfers and speciation. He contrasts the neo-Darwinian reductionists (Dawkins, et al) with a different bred of evolutionary biologist including Lynn Margulis, Erik Larsson, Luis P. Villarreal, Kwang Jeon, John Maynard Smith, Eors Szathmary, and others. He also recalls some scientists who pioneered the ideas of symbiosis but never got the credit they deserved and were virtually ignored by the Darwinian establishment. It is surprising to see how "blind" the evolutionists were and how hard it was (and is) for new ideas to gain a foothold in any scientific community. But that is the way it should be: a new idea is just a notion until it finds collaborative support by being tested scientifically.
The Gaia metaphor is perhaps the ultimate expression of symbiosis in that it involves the entire biosphere. Ryan recalls Lovelock's view that our planet with its atmosphere and self-regulating processes represents "an emergent property" of life "tightly coupled with the physics and chemistry of the Earth's environment." (p. 112) This view has yet to gain full acceptance in the scientific community, but as knowledge of the symbiotic and cooperative nature of life (instead of an emphasis on the competitive nature) becomes more widely known (and as the old scientists retire!) I think that will change. Ryan makes it abundantly clear that (to recall an expression I either dreamed up or cribbed from somewhere) "Everything works toward a symbiosis."
One of the bugaboos in natural selection has been the idea of group selection. This has been debated for many decades, but it is becoming increasingly obvious (and Ryan strongly supports this view) that group selection is a reality. Ryan reports on the work of David Sloan Wilson and Elliott Sober, who used mathematic models to demonstrate how group selection might work. (p. 255) I have argued elsewhere for group selection so I won't go any further than to note that the biosphere that survives versus the one that doesn't (either through pollution, madness, lack of foresight, inability to ward off incoming disasters, etc.) is selected.
The most controversial idea in this book may be Ryan's insistence that natural selection should be seen as "an editorial force" acting upon what he calls "the creativity of the Genome." (p. 265). He has German biologist Werner Schwemmler suggest a balance by noting that the "combination of the two explanations (Darwinian gradualism and symbiotic saltation)" together progress "toward a unified theory of evolution." If this is correct, the way we view biological evolution is going to change dramatically in the years to come.
Ryan makes a distinction between endosymbiosis and exosymbiosis, the former involving one genome living within another, the latter pertaining to relationships such as that between pollinating insects and plants. I want to add that the exosymbiosis between humans and our crops and domestic animals has been the essential factor in our becoming a new sort of creature, one that evolves culturally rather than biologically, and will within a twinkling of time evolve into something that we cannot yet envision because of this rapid cultural evolution. Perhaps, as some have suggested, we will form a symbiosis with our intelligent machines and let Darwinian evolution edit the result.
This is an exciting book, challenging and filled with information and ideas.