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Sex and Death: An Introduction to Philosophy of Biology (Science and Its Conceptual Foundations series)

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'Sex and Death' is a pretty ambitious book, being almost a survey of the specific, hot topics in modern philosophy of biology. Tackling such issues as the nitty-gritty, purely philosophical issues of gene selection vs. selection of the organism, the definition and nature of the concept of 'species', and "Life on Earth: the Big Picture", the authors have done a nice job of using a breathtaking array of references, from Dawkins to Gould, Lewontin to Mayr, Alexander to E.O. Wilson, etc.

Unfortunately, keeping all of this succinct makes for a somewhat dry presentation. I agree with the previous reviewer in that often the authors' presentation of concepts are difficult to grasp for those not already familiar with the topics; when more concrete examples are made, the point is much easier to take. Still, this is a minor complaint given the scope and rigor of the analysis presented.

If you're into the accessibility of a Stephen Jay Gould or Richard Dawkins, this book will be a challenge to read. In fact, it reminds me much more of Elliot Sober, one of the more famous Philosophers of Biology cited in this book. As 'an Introduction to Philosophy of Biology', 'Sex and Death' is more accessible than the work of Sober, and it is a well-organized and presented survey of the philosophy of biology, assuming that the reader has already had a fairly ample exposure to the subject. For the uninitiated, it would be better to bone up on Darwin, Gould, Dawkins, Lewontin, Mayr, and Wilson before trying to tackle this book; *frequent* references to these authors are made,and a close familiarity with their ideas is presupposed.

Gene selectionism. The most basic argument for gene selectionism is that genes replicate while phenotypes are temporary so selection of phenotypes cannot by itself produce cumulative change. But this is a gross oversimplification. Not only genes replicate, for offspring also receive cell membranes (only membranes make membranes), symbiotic organisms, and other biochemical stuff from their parent. Also, one can imagine situations where there is accumulation at the phenotypic level without accumulation at the genetic level (when a trait depends in a complex way on several genes). Better arguments for gene selectionism exploit weaknesses stemming the conventional view's reliance on the organism concept. Gene selectionism avoids this problematic concept which lumps together many diverse things (complex animals, single-cell organisms, plants, colonial organisms such as corals, etc.). This perspective suggests questions which the conventional view obscures, e.g.: Why are there organisms (considerable investment to build a body)? Why are cancers not so common as to undermine the viability of organisms? There is also the "extended phenotype" argument: the traits by virtue of which genes are selected need not be traits of the organism in which they are contained. E.g.: there are parasites which kill their host but induce it to leave a sexually attractive corpse, whence they find a new host by causing this trait in their original host. One may reply: but it is not the extra-organismic trait that is being selected for but rather the organism's ability to create it. However: what matters for (or "is visible to") evolution is the ends not the means, the outcome not the ability.

Critiques of gene selectionism. Something seemingly not captured by gene selectionism: suppose certain organisms have either of the genes A or B for traits and either of C or D for behaviours; and suppose that AC and BD are successfull combinations while AD and BD are not. There seems to be selection for neither of the genes A, B, C, D, only higher-order entities. The gene people reply that this is explained by frequency-dependent selection (i.e. frequency or A vs. B influences selection on C and D, and vice versa). Selection is already relative to many things---why not other genes as well? But why then not reduce all the way down to the four nucleotides? For gene selectionism to work a gene needs to have a phenotypic effect (in order to be visible to evolution). Its proponents used to define genes as reasonably-sized chunks of DNA ("evolutionary genes"), because this went well with their view of cumulative genetic selection. But the connection with phenotype would then be so indirect and variable that genes would be virtually invisible to selection. A better gene concept is needed but not provided. Some have tried to start at the other end and define genes functionally in terms of their phenotypic effects; but to serve as the basis for gene selectionism such "genes" must of course have a reality independent of the phenotypes by which they are defined, which is far from guaranteed.

Priority of genes. As noted, much more than genes are being passed on to offspring; further examples: bird's song, nest site and material; "host imprinting" (e.g. eggs laid on a specific plant which hatched organism memorises). Perhaps one should think in terms of "developmental systems" instead of narrowly focusing on genes. Gene selectionists need to show that genes are privileged over these other factors. Their main proposal is: genes are the only thing that carry information (this has even been phrased as a redefinition of evolutionary genes). But this is hard to define in a satisfactory way. For example one may say: genes have a specific intention unlike other developmental factors. But intentionality is difficult to define and conceive of materialistically. One may try a teleosemantic definition: intentional content is about what evolution has defined it to be about. E.g.: a rabbit's fear of certain cues has intentional content: "there is a predator here". But this definition applies to other developmental factors as well.

Group selection. Group selection faces problems: often almost impossible to test empirically (e.g. that hierarchies exist to minimise wasteful conflict); there are often equally plausible explanations based on individual selection (e.g. alarm calling shows the predator that you are a difficult pray); susceptive to subversion from within (by e.g. non-altruistic individuals, who have much shorter generations than the group and so overtake group selection). An alternative is kin selection ("inclusive fitness" included kin) which has some empirical support, e.g. eusocial insects with queen structure whose genetic structure is such that non-queeen females are more closely related to their sisters than their daughter which explains why they help the queen instead of breeding. A more abstract alternative is trait group selection, which sees anything with a common fate (common causal trajectory) as an interactor; e.g. (im.), crickets paddling pairwise to cross pond. This view subsumes kin selection and reciprocal altruism as special cases. It need not be susceptible to subversion from within because trait group selection need not be slower than individual selection. Another view: population structure is part of the environment; altruism may evolve through selection for individual fitness given that the environment includes many altruistic individuals. This can also subsume previous views, but it can be criticised for not being explanatory, not accounting for the process only the results (same "averaging fallacy" as naive gene selectionism).

Adaptation. One should not assume that any successful trait is the result of specific selection; this would be to look at organisms as "mosaic of traits," ignoring interconnections. Developmental constraints (entrenchment) rather than adaptive value seems to explain why all mammals have almost identical ear bones. An alternative to adaptationism which does better at explaining this sort of thing is explanation by classification, in analogy with the periodic table of elements.

Human behaviour. It is difficult to study human behaviour from an evolutionary point of view for a number of reasons: relatives extinct; no invasive experiments; environment has changed; hard to identify trait units (has e.g. aggression evolved as one trait or several more specific ones?). Proposed evolutionary models of human behaviour suffer from weaknesses in addition to these. Evolutionary psychology (e.g.: male promiscuity and female coyness may be explained by their different investment costs in reproduction) is based on an adaptationist point of view and ignores the interactive character of social evolution (assumes fixed problems). Some have tried to apply evolution to ideas (ideas compete, replicate and evolve) but this ignores the fact that evolution depends on the rate of mutation being just right (also, evolution explains apparent design so why apply it where there is actual design?).

This is a brilliant book in that it is written simply but covers the important aspects of the philosophy of evolutionary biology. This book could be the foundation of a philosophy of biology course at university level, but still would appeal to the layman interested in the thought behind biology. It is more technical than many popular biology books, but that is because it is so loaded with content. It is definately worth buying and persevering with. To frame this assessment, I have studied to postgraduate levels in both philosophy and evolutionary biology and enjoyed the book thoroughly. Friends of mine who are not specialised in this area but have some knowledge of biology also found this book enlightening.

As a comparison Elliot Sobers' the Philosophy of Biology goes over a lot of similar territory and is also well written - I would also highly recommend it. Of these two books which are both excellent, Sex and Death has a more conversational relaxed style and would probably have a more general appeal.

The other good book in this area which I have read is Alex Rosenburg and Daniel McShae's Philosophy of biology and this has a more technical intonation than the other two books mentioned and is definately geared towards philosophy students rather than the public.

Sex and Death is as close as you can come to a simple book popularizing the philosophy of biology.

Conceptually, evolution theory seems simple:

Individual organisms vary in their various traits. Some are better adapted to survive in their environmental niche than others, because they possess (more and/or more highly) adaptive traits. Because the better adapted organisms succeed disproportionately in begetting offspring, the adaptive traits become more prevalent in the next generation. Over many generations, this process of filtering and concentrating the heritable traits of organisms has spawned diverse forms of life, with genes transferring traits from parents to offspring.

I think I squeezed in all the relevant keywords.

This description works at an abstract level, but close up, the theory's fuzziness becomes apparent. What is a niche, anyway? Or an adaptation? Or a trait? Or an organism? Or a gene?

These questions make Kim Sterelny and Paul E. Griffiths' Sex and Death a worthwhile read for anyone interested in probing the rigor of the received view. It turns out that researchers in the biological sciences have yet to settle on agreed-upon definitions of the above terms. Evolution theory is compromised by its own hazy vocabulary.

For example, do ecological niches exist independently of the organisms that fill them? Or are they defined by their occupants? Is average temperature sufficient to define a niche? Temperature and water salinity? Temperature, salinity, and the density of predators? "Niche" is, if not an essential, at least a supporting concept in evolution theory, but it amounts to a conceptual blur. Nobody can say what the necessary and sufficient conditions are to define a "niche."

Organisms have many "traits." But are they all "adaptations"? If so, why bother calling them "adaptations"--if it's just another word for "trait"? If some traits are not adaptations, then what criteria can we use to distinguish those, presumably incidental, traits from adaptations? Nobody knows.

But then we have to ask, what counts as a trait? A compound eye? Or just the lens? Or the eye plus the optic nerve? That is, what's nature's granularity when it comes to carving up organisms into more and less adaptive "traits"? The theme of this "grain problem" runs throughout the book. At every turn, the authors use it to unsettle the received view.

While we're at it, what counts as an organism? An ant? But a lone sterile worker has no capacity to beget offspring. Or, is the whole ant colony the organism (sometimes called a superorganism)? The authors underscore the "organism" problem with other examples from the invertebrates,

"Some colonial organisms also have bizarre life cycles. The Siphonophora--jellyfish-like colonial hydrozoans such as the Portuguese man-of-war--are so integrated that it is hard to say whether they consist of many cooperating organisms or a single organism. The various cells (the zooids) within the man-of-war are specialized: there are floatation specialists, propulsion specialists, killer cells, and sex cells. In this respect, the man-of-war seems to be a single organism. On the other hand, each cell within the colony has an independent origin in a fertilized egg. In contrast to the zooids that jointly form a man-of -war, cellular slime molds spend most of their life as independent cells. But when food runs out, they aggregate into a single body, which develops specialized parts. Some of the cells form a stem, ending in a group of cells that specialize in making spores. So these cells too seem to spend part of their life as individual organisms, and the rest as parts of an organism."

And it's not just invertebrates that pose the problem. Ninety percent of a human body's cells are bacterial, not human. So, what constitutes the human "organism"?

"Gene" probably is the least salvageable term. In the early days of post-Crick-Watson genetics, a gene was taken to be a contiguous sequence of nucleotides that coded for a particular protein, the one-gene-one-protein model. But as scientists discover protein synthesis to be a remarkably complex process, that model has gone up in smoke. It's not clear that anything discernible in a strand of DNA corresponds to "genes."

Log onto a news website, and watch the content load. The page you get is a mosaic of content pulled from news servers, ad servers, filters and recommenders of various kinds. The content served is the product of dynamic algorithmic operations. Nothing in the system of servers and databases corresponds to the static concept of "page," and the same appears to be true when it comes to protein synthesis inside cells. Nothing in the system of DNA's servers and databases corresponds to "gene."

So the theory of evolution rests on a bed of semantic mush. The theory seems to boil down to saying merely that, if you wait long enough, life's forms diversify. The lack of definition of its operative terms is a significant breach in the edifice of the theory, I think.

Have the Intelligent Design advocates effectively exploited the breach? Misguided as the scriptural literalists among them are, the IDers perform a service by holding the scientists' feet to the fire. So there you have it, IDers, Go sock it to `em!

The subtitle of Sex and Death is "An introduction to philosophy of biology." What a reasonable place to start.