Acquiring Genomes: A Theory of the Origins of Species
Lynn Margulis and Dorion Sagan
Foreword by Ernst Mayr
2002: Basic Books, New York.
The basic premise is that species evolve due to the acquisition of alien genomes. Mayr, in his Foreword, disclaims this, warning that there is no evidence of such species formation beyond the bacterial level. The only mammalian example offered by the authors is circumstantial: the cow, with its special stomach and ability to digest grasses due only to the presence of certain bacteria.
An example of genome acquisition, which would also serve as a nifty character attribute of Gargantua Slime: Certain slugs (for example Elysia viridis): “The ancestors of these slugs have eaten but not digested certain green algae, which years ago entered the tissue of the animal—and stayed there.” These slugs are green due to the presence of the algae. “These underwater slugs need not seek food. Rather they crawl near the shore. They never eat throughout their adult life. The slugs, newly evolved green animals, now sunbathe in the way plants sunbathe” (13). In other words (though the authors don’t specifically say this), the slug-algae photosynthesizes the needed food-energy that keeps the slug going. “A second example is lichen…” (13), a fungi co-evolved with a cyanobacterium.
“Ultimately, an anthropocentric term like ‘competition’ has no obvious place in the scientific dialogue. Rather we would propose a new search in the social sciences for terms to replace the old, tired social Darwinist metaphors. If survival is owed to symbiosis, rather than overemphasized intraspecific competitive struggles, what then are the consequences for nonbiologists interested in evolution” (15). They never answer this question and continue to use anthropocentric metaphors throughout. “Competition implies an agreement, a set of actions that follow rules, but in the game of real life the ‘rules’—based on chemistry and environmental conditions—change with the players. To compete, people—for example on opposite teams—must basically cooperate in some way. ‘Competition’ is a term with limited scientific meaning, usually without reference to units by which it can be measured” (16). “The entire panoply of neodarwinist terminology reflects a philosophical error, a twentieth-century example of a phenomenon aptly named by Alfred North Whitehead: ‘the fallacy of misplaced concreteness’” (16). Thus: “What is Richard Dawkins’s selfish gene? A gene is never a self to begin with” (16). We must always think in terms of individuals and populations, especially as cells, as Mayr reminds us in his Foreword. “The time has come in serious biology to abandon words like competition, cooperation, and selfish genes and replace them with meaningful terms such as metabolic modes (chemoautotrophy, photosynthesis), ecological relations (epibiont, pollinator), and measurable quantities (light, heat, mechanical force)” (16-17).
One of the main themes of the polemic first 50 pages of the book (esp. in the chapter “Darwinism Not Neodarwinism” is “The Myth of the Independent Individual.” This is the idea that we “are really walking assemblages” (19)—surreal beings! “We humans, like all organisms, live embedded in ecological communities” (19). “We imagine that pathogenic microbes attack us, but if such pathogens are part of the committee that makes up each of us to begin with, isn’t health less a question of resistance to invasion from the outside and much more an issue of ecological relationships among committee members? Yes” (19). But, as with their use of the word “game” (of life) above, the metaphor of “committee members” is one of misplaced concreteness. The problem is one of semantic roles, and the natural affiliation of speakers to employ terms of agent and patient.
Compare this with Dickinson’s poem “Four Trees”: “The book What Is Life? (Margulis and Sagan 2000) has a photo taken from a distance by Connie Barlow that shows a stand of poplar trees in Colorado. Anyone can count these trees—there are hundreds if not thousands of them. But although it has many parts, this stand is really only one single organism. Under the ground the ‘tree’ is continuous. It forms a connected structure with many upright shoots that emerge from the soil, straining our everyday notion of a single tree. The ‘individual,’ whose roots are completely continuous, extends for kilometers laterally and for meters into the ground and up into the air vertically. This poplar stand is believed to be one of the largest ‘organisms’ alive today” (21). That is, the poplar grove is one organism at the level of the “rhizosphere” (21). (Cf. Delueze and Guattari.)
One of the problems of modern evolutionary theory, the authors claim, is that it based on observation and analysis of mammals, especially the large charismatic animals. “Although zoocentrism may be adequate for the kinds of mammals that are deployed for breeding further populations of mammals, it is a tame approximation—a kind of Apollonian hallucination—of what is going on with life as a whole” (22).
The thermodynamic gradient: “A gradient is difeined as a difference across a difference” (45), which, in Bateson’s definition, would mean a gradient is information. Without such a gradient, entropy sets in and causes systems to “become random, disorganized, less complex over time” which was long thought to contradict living systems. That is, living systems seemed to defy, or not be subject to the laws of, thermodynamics. But “Life does not exist in a vacuum but dwells in the very real difference between 5800 Kelvin incoming solar radiation and 2.7 Kelvin temperatures of outer space. It is this gradient upon which life’s complexity feeds” (46). “The biosphere… has [the] overall dimensions of a hollow sphere some twenty-three kilometers wide. This, compared to the 6371 km radius [of the planet], corresponds to only 0.0007% of the volume of the planet” (38). “Like the chemical Bénard cells, which stabilize by defying statistical tendencies to approach equilibrium because they manifest the improbably gradient around them [???], or the meteorological whirlpools that maintain their structure ‘to’ get rid of an atmospheric pressure difference, life to is a gradient-reducing system” (46). (See E.D. Schneider and J.J. Kay, 1994, “Life as a manifestation of the second law of thermodynamics.” Mathematical Computer Modeling, 19, no. 6-8: 25-48.) As with the Bateson connection, “This new thermodynamics (sometimes called homeodynamics) lets us begin to glimpse the path from matter (gradient breakdown) to mind (gradient perception)—from energetic to informational ‘self’-organization…. The tendency of systems to organize comes from the gradients in their immediate surroundings, not from their own internal components. The informational structure of life, carried in DNA, has become self-sustaining via reproduction. But memory exists as well in fully nonliving systems such as vortices organized by rotational pressure gradients. These jump to new states and new values that depend on their history” (48-49). To cast this in dangerously anthropocentric terms, one might say that the purpose a of system is gradient-reduction. “As natural selection filters out the many to preserve the remaining few, those few ever more efficiently use environmental energy to ‘purposefully’ reduce their gradients. The key point is that living and nonliving ‘selves’ come into being to reduce gradients naturally. The reproducing self of biology is a higher-order cycle whose antecedents can be inferred from the cycles of the nonliving world. Nucleotide replication and cell reproduction do not emerge from nowhere. They are born in an energetic universe from thermodynamic tendencies inherent in nature” (49-50).
A eudaimonc quip: “Joseph Leidy, sage of nineteenth-century Philadelphia and one of the founders of that city’s Academy of Natural Science, summarized his philosophy of a good life: ‘How,’ he wrote, ‘can life be tiresome when these is still another rhizopod to describe?’” (56). A rhizopod is an ameba.
“Prokaryotes, whether archaebacteria or eubacteria, … all belong to a single worldwide species. The bacterial Internet preceded ours by 3,000 million years!” (58). A very blatant example of “misplaced concreteness”! And probably simply wrong, as the Internet is no way is a “single species.” But the point they are making is that these non-nucleated bacteria are not a species, or at most, are a single species. “An organism (A) belongs to the same species as another organism (B) if and only if A and B have precisely the same cellular ancestors, that is, they are descended from the same genomes, and the relations between these genomes are the same” (58). This is a corollary of Mayr’s definition of a species: “Two organisms belong to the same species if they recognize each other, can mate, and can produce fertile offspring” (58). But how can cells “recognize” each other? What this book never mentions is semiosis.
Another of their critiques of the standard model of evolution is the mutation theory. The standard model has it that new species, on the one hand, are created by mutation, but, on the other hand, that most mutations are fatal. (71-72)
The Botany of Desire: A Plant’s-Eye View of the World
