Acquiring Genomes: A Theory of the Origins of Species (Paperback)

Extending Margulis' earlier thesis that cellular organelles were the result of symbiotic relationships, the authors attempt to make "symbiogenesis" replace natural selection. Symbiosis reflects two organisms existing together and mutually dependent. Like Lego pieces they may enjoy individual identity which changes when they're assembled. Margulis and Sagan stress that symbiosis is far more prevalent than a fungi and algae forming lichens on rocks. With many vivid examples, such as green slugs that never eat or a marine organism that "shoots" predators with bacterial ribbons, they stress that the ubiquitous nature of symbiotic relationships "proves" gradual evolution by genetic variation is misleading. Instead, they propose a saltationist approach - new species can be formed as rapidly as the symbiotic relationship is stable.

Margulis derides Darwinist scholars for focussing on extinction, even going to the extent of counting the synonyms for "death" in Darwin's Origin. Arguing that natural selection doesn't "create" new species, she further contends science has never demonstrated the emergence of a new species. She scorns the work of Peter and Rosemary Grant in the Galapagos [featured in Jonathan Weiner's "The Beak of the Finch"] as failing to demonstrate evolution of new bird species. Margulis cannot seriously expect the emergence of a new bird in two decades of study. However, since she contends symbiogenesis can be achieved in a single generation, such extravagant demands aren't surprising. Although she suggests environmental pressures can force symbiotic relationships to emerge, she rejects the notion that these same pressures can winnow life to leave survivors as a new species in the changed circumstances.

While the book is an informative and provocative read, Margulis and Sagan spend nearly as much time ranting about the failures of Darwin and Darwinists as they do presenting evidence for their thesis. As with many polemicists, the authors erect the occasional straw man. In this case, as advocates of Eldredge and Gould's "punk eek" concept, they assault any aspect of sociobiology targetable. Among other false claims, they contend sociobiologists assert altruism among individuals is "monitored." Overzealousness leads them into the occasional blunder, claiming that genes don't produce cells because cells are mostly protein. The job of all genes is to express proteins. Finally, as they have done elsewhere, the pair insert a lengthy support for Lovelock's Gaia thesis. In this case, the section is an abrupt non-sequitur providing no relevant information supporting their thesis.

There's no question of the authors' prose abilities. They present a wealth of new information on microorganisms, all of which makes compelling reading. In too many cases, however, there are few or no references to sources. The assertion that certain mushrooms possess "thousands of genders" may be old news to biologists, but it was a first for me. Yet there is no citation for this information. The illustrations are interesting, but poorly tied to the text. In short, this book presents numerous challenges and topics for further investigation. Margulis and Sagan may have outlined how the methods of natural selection may be expanded, but they have hardly replaced Darwin's original thesis with this effort. [stephen a. haines - Ottawa, Canada]