C. U. M. SMITH

social conditions likely to appear in our civilization the very psychological and socialmake-up of human beings bodes well for the practice of science. For Hull's mechanismdoes not make scientists into any more than the flesh-and-blood human beings that theyare, while telling us that, precisely because human beings are as they are, conceptualinclusive fitness and the demic structure of science will work to keep science honest. I donot buy everything that Hull has to say on this point, but I think that his valuablecontribution is more than a step in the right direction.

I would like to close with two small points. The first is that the adaptability of science ofwhich I have spoken ought to be ascribed not to individual scientific ideas, but rather toour capacity for science itself. Most scientific ideas have of themselves little practicalutility, but they play a part in an enterprise which as a whole permits us to deal with theworld in a manner that can have great utility (Munevar 1981, Ch. 4). The second point isthis. I have rejected some of Hull's proposals, his analysis of selection, for example. And Ihave placed some of his proposals within a context more amenable to my own view ofthings. To manage this last I have given a sketch of my own biological epistemology,without elaboration or defense. In that sketch I have made reference to the crucial role ofcuriosity, a role that I have tried to explain. By not taking curiosity for granted, as Hulldoes, I think that some important aspects of the nature of science come to light. Now, thereare two human drives that Hull takes for granted: the scientists' curiosity and their desirefor credit for their contributions to science (p. 154). In my own work I have placed greatemphasis on explaining the first of those characteristics of scientists. As for the second, Iwould like to suggest a very tentative hypothesis. In my view (Munevar 1981, Ch. 4, and ina forthcoming book, The Dimming of Starlight, Ch. 3), I give an account of science as play;and I suspect that if we consider science in that light, it may be easier to understand whydesire for credit, so prevalent in other forms of play, could achieve a significant role in thepractice of science. Of course, desire for credit is present in many human activities, butHull needs it to be in science more than in most others.

Send Reinforcements We're Going to Advance

C. U. M. SMITH

Department of Vision SciencesAston UniversityAston TriangleBirmingham B4 7ET, UK

Charles Darwin visited the Galapagos islands in September/October 1835; he returned toEngland in 1836 and read Malthus' Essay on Population in September 1838; it was onlytwenty years later that the fateful communication from A. R. Wallace goaded him intopublication. As Professor Hull says, it is one thing to sketch the general outlines ofevolution by natural selection; it is quite another to detail a precise mechanism.

Darwin published a joint paper with Wallace in 1858 and went on to publish TheOrigin of Species in 1859 but it was only after another decade had elapsed that hepresented the full evidence for his theory in the 1868 Variatiop of Animals and Plantsunder Domestication. Professor Hull's paper is thus comparable to the Darwin/Wallace

Biology and Philosophy 3 (1988) 214-217.C 1988 by KluwerAcademic Publishers.

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paper of 1858 - a foretaste of riches to come. Similarly it does not contain the fullevidence and this makes it a little difficult to comment. It may be that my response will finda complete answer in the promised Science as Progress: An Evolutionary Account of theSocial and Conceptual Development of Science.

It may be, however, that the analogy which Professor Hull draws between his forth-coming book and the Darwinian opus is too close for comfort. For The Origin of Specieslacked a crucial element; it lacked, precisely, a mechanism. However was the variationwhich was fundamental to the theory produced and inherited? This hiatus was immediatelyseized upon by Bishop Wilberforce. In the courteous but passionate critique which hepublished in The Quarterly Review (1860) he writes ". . .we must be shown that there is anactivity at work in nature, co-ordinated with the law of competition and with the existenceof such favourable variations, a power of accumulating such variations through successivedescents ... failing this" he goes on "the whole theory falls to pieces" (p. 234). Othervoices made the same point (for instance, Jenkin 1867). Darwin took these criticisms toheart.

Darwin's analysis of heredity was largely confined to the higher animals. His extensiveanalysis of the records of stockbreeders and pigeon fanciers which had done so much toestablish the notion of evolution by selection had impressed him with the fact that hybridstended to exhibit a mixture of the characteristics of both parents. "When two commingledbreeds exist at first in nearly equal numbers" he writes in Animals and Plants underDomestication "the whole will sooner or later become intimately blended" (2,398). But'blending inheritance', as Fleeming Jenkin (1867, esp. pp. 289-92) and others pointed out,would very rapidly swamp any initial variation in a population. Indeed Darwin himselfwrites (using very much the same example that Jenkin used) that after three centuries acolony consisting initially of equal numbers of whites and blacks would be almost entirelymulatto. Darwin still needed a mechanism: a mechanism to produce and to continue toproduce a large quantity of new variation.

Darwin (1868), of course, solved this problem by his 'provisional hypothesis' ofpangenesis. This was straightforwardly Lamarckian in its connotations. As such it hasdropped out of orthodox biology. What was happening in heredity was worked out byGregor Mendel. And this is where we return to Hull's theory. For the essence of Mendel-ism is particulateness, the inverse of blending. Although the biology of the second half ofthe twentieth-century has revealed the gene in its full molecular complexity, and although itis true as Hull says that at the molecular level they can no longer be regarded as 'beads ona string',' nevertheless so far as population genetics is concerned, so far as the 'modernsynthesis' of evolutionary biology is concerned, this is just how they are treated.

Moreover even at the molecular level 'start' and 'stop' signals ensure that the lengths ofDNA corresponding to classical 'structural' genes (and other types of gene, for that matter)are clearly demarcated. Molecular geneticists, as much as population geneticists, find(indeed depend upon) 'particulateness'. Most mutations, too, are 'point' mutations. In thiscase the 'particles' are nucleotides and, in particular, nucleotide bases. The pairing prop-erties of the bases may change, mutate, but they never 'blend'. Furthermore the rates atwhich mutations occur varies from one gene to another. Some proteins thus evolve muchmore rapidly than others. Fibrinopeptides change rapidly; the histones relatively slowly.These rates, moreover, in contrast to the implication of one of Hull's statements, have littleto do with 'generation time', everything to do with 'elapsed' time (Wilson et al., 1977).

The biologist's theory of evolution is thus essentially an 'atomic' theory. If this theory isto be used as a paradigm, or even as a metaphor, for the conceptual development ofscience it seems to me vitally important to identify what correspond to the Mendelian'factors', the genes. And this, it seems to me, is where Hull's theory, at least as outlined inthe present abridgement, is lacking.

For what is being selected? What are these 'memes' whose changes in relative fre-

C. U. M. SMITH

quency, according to Hull, constitute conceptual change? Dawkins (1976) in introducingthe term, provided the example of 'tunes, ideas, catch-phrases, clothes, fashions, ways ofmaking pots or of building bridges' (p. 206). Hull, it is true, maintains that 'everythinginvolved in selection processes and everything that results from selection are spatio-temporal particulars' and that 'individuality is at the heart of the selection process'. Butindividuals, as he is the first to point out, are very variable. Certainly the best knowninstance of individuals, ourselves, have nothing like the unchangeableness of Mendelianfactors. Hull's examples of memes (and, as mentioned above perhaps a fuller exemplifica-tion will be presented amongst the data promised in this big book) fail to convince. 'Theentities which get passed on' he writes 'are beliefs about the goals of science, the properways to go about realising these goals, problems and their possible solutions, modes ofrepresentation, accumulated data reports etc.'

This, of course, is unexceptionable. No one would deny that these things are passed onand change with the passing on - in other words, in a loose non-Darwinian sense of theterm, 'evolve'. But I doubt very much that any of them can be pinned down and treated ascomparable with particulate Mendelian factors, genes or nucleotide bases. Each replica-tion, says Hull, 'counts as a generation with respect to selection'. Yet, in contradistinction,to the neo-Darwinian theory of evolutionary biology, each replication does not (as it doesin the vast majority of biological cases) result in two identical copies. Everyone knows thatwhen the request to 'send reinforcements' was passed down the line the message ended upas 'send three-and-fourpence we're going to a dance'!

This feature of memetic replication relates, of course, to the quasi-Lamarckian natureof conceptual evolution. Hull, indeed, argues at some length that conceptual evolution isnot Lamarckian. This section of his paper seems to me somewhat strained. If the mere'advance' is transformed after several replications to 'a dance', and memes as Hull agreesare to be compared with genes, then it does seem that the meme (= gene) has beenaffected by the 'scrutiny' (to use Darwin's term) of the environment to which it hasbeen exposed. Memes are not blind, 'windowless', monads. To carry the analogy to themolecular level one would have to say that with memes there is 'reverse translation' from(in the example) expression (speech) to structure (concept).

Although 'reverse-transcription' is well known to molecular geneticists, 'reverse-transla-tion' is (for excellent biochemical reasons) never found.2 If it were not for this biochemicalportcullis Lamarckian-type inheritance of acquired characteristics, so much more rapid andefficacious a means for evolutionary change, might well have long ago overtaken theMendelian hit-and-miss mechanism. Perhaps, indeed, with the memes it at long last has!(Bonner 1980, p. 34). Perhaps we should dust off Darwin's 'provisional hypothesis' ofpangenesis and see how far it could form a paradigm for meme-based evolution!

There are many excellent things in this paper and I for one look forward to reading thebook. But on this central issue I feel that Professor Hull has not advanced beyond hisfellow evolutionary epistemologists. Until and unless we can discern in the tangled bank ofscientific discourse the atomic elements which 'mutate', 'combine', and 'recombine', togenerate the growth of new thought the attempt to use the powerful and sophisticatedanalyses of neo-Darwinism to account for the evolution of science will remain Procrustean.To adapt another of Ivy Compton Burnet's titles, genetics and memetics remain two worldswith different ways.

NOTES

Hull remarks that the 'Because crossover does not respect the boundaries of thesefunctional units, the chunks of genetic material that are transmitted intact are highlyvariable'. This could be misleading. Crossovers do not respect the boundaries between

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genes, true, but a fragment of a gene is never transmitted. The result of an intragenecrossover is a (chance) recombination of the two parental alleles. Anything less or morewould (in general) be unviable. It is true that molecular genetics has revealed greatcomplexity in structural genes (exons, introns, insertions and deletions) but the stretches ofDNA which form the molecular bases of a given gene do not (in general and in the shortterm) vary is length.2 In all contemporary organisms, from bacteria to man, the translation step in the infor-mation flow from genotype to phenotype is an enormously complex affair involving threetypes of RNA and multitudinous enzymes. It is extremely difficult to see how it could bereversed. It is this biochemical 'brute fact' which prevents information proceeding fromphenotype to genotype and hence blocks Lamarckian-type evolution.

Mere Generality is not Enough

WIM J. VAN DER STEEN*

Departments of Biology and Philosophy,Free University, Amsterdam;Institute for Theoretical BiologyLeiden State UniversityThe Netherlands

and

PETER B. SLOEP

Department of Natural Science,Open University,The Netherlands

Fire-flies do it by light signals. Unable to fly the females just wait for the males, who canfly, to come. The light signals of a female attract a male fire-fly who, after the proper,species specific exchange of signals, will approach the female and copulate with her. That'show fire files multiply. Although it is easy to miss the analogy, traffic lights multiply in asimilar fashion. If they become operative at the most dangerous intersection in town, trafficcongestion will result. Other intersections will become dangerous and they too will getlights. That's how traffic lights multiply.

Traffic congestion is admittedly not in all respects like copulation. But they share aproximate cause, light signals. And the effect, multiplication, is the same in either case. Thecorrespondence is mostly overlooked because our current concepts are inappropriate.Once proper concepts are introduced it becomes possible to develop a general theory. Fora start, copulation and traffic congestion will have to be conceptualized as replicationmediators triggered by visual reproductive signals.

* Address for correspondence: Department of Biology, Free University, PO Box 7161,1007 MC Amsterdam, The Netherlands.

Biology and Philosophy 3 (1988) 217-219.0 1988 by KluwerAcademic Publishers.