Stephen Jay Gould's account of macroevolution in a new Encyclopedia of Evolution interests us. He argues that the basic Darwinian mechanisms that produce microevolution do not adequately account for some of the more substantial steps in evolution, and we emphatically agree. He observes, "An anatomically degenerate parasite, reduced by natural selection to little more than a bag of reproductive tissue in the body of a host, may be just as well adapted to it's local environment as the most admirably evolved organic machine for running, swimming, or flying" (p E-26). Again we agree.

Then he offers two detailed examples in which additional mechanisms would be needed to explain macroevolution. The first one invokes genetic "hitchhiking" to promote a trend towards smaller body size along with an advantageous trait such as a higher speciation rate. (Do changes in body size exemplify macroevolution?) In Gould's second example, catastrophic mass extinctions explain the emergence and dominance of species that might remain subordinate or go extinct under normal circumstances.

Neither of Gould's examples deals with macroevolutionary progress, but only backward steps — reduced body size or extinction. He offers no account for the new genetic programs needed to produce "running, swimming, or flying." In our opinion, this lack is symptomatic of the big flaw in the darwinian account of evolution: it does not adequately account for sustainable macroevolutionary progress. (Why doesn't Gould mention horizontal gene transfer?)

Gould's six-page essay, "Macroevolution," is one of nine "Overview Essays" by distinguished scientists introducing the new, two-volume encyclopedia. Among its roughly 350 entries, "panspermia" is not included.

Chapter 1 begins with a visit to The Museum of Creation and Earth History, and moves to a well-paced, informative history of origin-of-life research. That the chemical ingredients of life may have been delivered from space (pseudo-panspermia) is now a completely respectable hypothesis, we read. Also, eminent researcher Leslie Orgel "believes that living organisms may travel from world to world." But he remarks, "All theories are bad."

Chapter 6, subtitled "Chance and Necessity in the Origin of Biological Complexity," is based on interviews with Orgel, Gerald Joyce, Stuart Kauffman, Stephen Jay Gould and Simon Conway Morris. Here we noticed an example of a longstanding confusion: in fitness landscapes, what does the vertical axis measure? The authors state plainly, "The height of the landscape at each point represents the 'fitness' of that possible organism: roughly speaking, how many offspring is it likely to leave." If so, of course, simpler lifeforms like bacteria would occupy the peaks. But the authors promptly say that the challenge of ascending the peaks is a different one: "How do you get complex structures like eyes?" So now the vertical axis measures organized complexity? But the two measures — likely number of surviving offspring, and organized complexity — are almost diametrically opposed. This confusion can mislead us into thinking that if mutations can increase "fitness," they can also increase organized complexity. Yet the latter phenomenon lacks experimental confirmation. [Thanks for the book, Dave Bowman!]

• Barbara McClintock dicovered TEs in maize the 1940s, naming them "controlling elements" because they were able "to regulate gene expression in precise ways."
• TEs can ...make significant contributions to the evolution of their hosts.
• TEs are DNA sequences that have the capacity to change genomic locations.... Initially there is a rapid invasion phase....
• Class I TE's — retrotransposons, retroposons, and retrointrons — are similar to retroviruses, using an RNA-mediated mode of transposition, and encoding a reverse transcriptase. Class II TEs — transposons as originally, narrowly defined — use a DNA-mediated mode of transposition.
• Identifiable TEs make up approximately 35% of the genome of [humans]... and possibly as much as 50%.
• TEs can be transferred horizontally between species.... The specific mechanisms responsible for horizontal transfer of TEs remain elusive.
• Parasitic elements, such as transposons and introns, might have provided the genes responsible for the sexual cycle in eukaryotic organisms.
• TEs may have played a major role in... the origin of eukaryotes and the origin of vertebrates...[by providing] the driving force for... chromatin formation and methylation.
• Although simple DNA base substitutions are well suited for the generation, diversification, and optimization of local protein space..., a hierarchy of mutational events is required for the rapid generation of protein diversity.... Because they are uniquely competent to reshuffle DNA sequences, TEs and viruses are important generators of the more complex types of mutations in the mutational hierarchy.
• TEs may play a significant role in genome reorganization by promoting the insertion of other gene sequences....
• There is evidence for specific targetting [by TEs] of some heterochromatic regions.... Different elements have distinct insertional preferences.... Heterochromatin proteins can recognize and silence transposable elements.
• Recruitment may occur long after the elements entered the host genome; these sequences may even have lost some of the features that distinguish them as of TE origin.
• The propensity of these elements to insert into (and in some cases, even make up) the regulatory regions of genes... suggests an important role in host regulatory evolution.
• A series of TE-associated mutations exemplifies the potenetal for TE-mediated "rewiring" of regulatory networks.
• The adaptive integration of a short piece of DNA into a complex regulatory network... might be considered to represent an evolutionary process that has been common in the evolution of increasingly complex forms of life.

We were especially interested Mayr's account of the origin of new genes, which he names as a subtopic (p 38). He blithely explains that new genes are produced "most frequently, by the doubling of an existing gene," as if this theory were as well established as the structure of DNA. Actually, it was never well-established, and recent evidence casts doubt on it. But apparently, Mayr is not really very interested in the genetics underlying evolution. At one point he has the genomes of humans and bacteria too small by a factor of 1,000 (p 107), although he has them right elsewhere (p 38). He even writes, "It was one of the unexpected happy discoveries of molecular biology that molecules evolve just the same as do somatic structures" (p 34). He thought evolution could occur without genetic changes? And he mistakenly believes, "No selectively valuable contributions are known for any [transposable elements]" (p 100).

In Mayr's discussion of adaptation he writes, "new adaptations are ordinarily acquired quite gradually" (p 155). Later, about macroevolution he again emphasizes gradualness (p 190). Then he writes, "In spite of its gradualness, macroevolution is characterized by numerous major inventions..." (p 203). He is not concerned that this gradualism would somehow have to be tied to gradualism at the genetic level. That is, genes would have to gradually acquire the programs for those new inventions. But this gradual re-programming process has not been observed, nor has good evidence for it accumulated. Mayr ignores this problem completely. But so does almost everybody.