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"Lost" Genetic Information
True biological novelty can be found in many of the adaptive radiations that Explore Evolution describes. Despite this, the authors insist "There are many examples of isolated islands that are home to flightless birds and insects that have clearly lost some of the genetic information necessary to produce the traits possessed by their ancestors. Large-scale macro-evolutionary change requires the addition of new genetic information, not the loss of genetic information" (p. 77). No evidence is offered of research on the genetics of flightlessness, and it is far from obvious that flightlessness must represent a loss of information. It is not generally true that loss of a structure involves loss of genes; eyeless cave fish lose their eyes because certain genes are over-expressed. Furthermore, there is no basis for their claim that macroevolution requires the addition of new genetic information, nor is new genetic information beyond the capacity of normal evolutionary processes. For a fuller discussion of the problems with Explore Evolution's treatment of "information," please see chapter 8.
We saw previously that the variation within Hawaiian Drosophila and other adaptive radiations is far greater than the variation found within some much broader taxonomic groups. It is difficult to say what genetic information the authors of Explore Evolution believe was lost. For instance, in the example of damselflies above, here is how one researcher put it in 1970:
This change from aquatic to semi-aquatic to arboreal to terrestrial habit has demanded considerable morphological and physiological change in the gills, and there is a beautiful transition series displayed by the gills of the various species from the long, thin, delicate, highly tracheated gills of the aquatic forms to the short, thick, opaque, densely hairy gills of the terrestrial species. There must also be changes in the function of the spiracles.
"It would appear," he concludes, "that it is from such extraordinary adaptive radiation that new major taxa might be produced, and the phenomenon is here demonstrated most lucidly before our eyes."
While the full set of genetic changes underlying this evolution are not fully known, there is no reason to believe it required any new genes, nor that any existing genes were lost along the way. Like many cases of the evolution of new structures (for instance, those discussed by Armin Moczek. 2008. "On the origins of novelty in development and evolution," Bioessays, 30(5):432-447), the evolutionary process most likely operated by rearranging and reusing existing genes and regulatory systems, making changes to the places where genes were expressed, or the times when they turned on or off. Such subtle changes can produce dramatic effects on the final form of an organism.
Understanding the precise genetic basis for those sorts of changes has been an important area of research over the last few decades, as new technology made it possible to examine the ways that genes control development. Explore Evolution presents such open areas of research as a reason to abandon all hope of resolving the underlying issues, but this is not how science works. Scientists are actively investigating the ways in evolution actually works, and students who hope to participate in the active research under way as researchers, doctors, or patients need to understand the process by which scientists produce and evaluate new knowledge. A competent textbook would use these areas of active research to invite true exploration of novel ideas. The fact that Explore Evolution despairs of finding explanations for unresolved issues in science is a damning indictment of the book's inadequacies.