© Nature Publishing Group 1985 _________________________ What's the matter? Niles Eldredge The Problems of Evolution. By Mark Ridley. Oxford University Press: 1985. Pp. 159. Hbk £12.50, $19.95; pbk £3.95, $8.95. PROBLEMS in biology, in sharp distinction to those of philosophy, are solvable- or so writes Mark Ridley in the preface to The Problems of Evolution. Ridley has organ- ized his book around a series of ten Great Problems currently (albeit, he says, time- lessly) besetting evolutionary biology, problems that curiously decrease in their apparent solvability quotient as one ascends the scale of biological complexity and at the same time approaches the end of the book. Ridley's preoccupation with the answers to questions imparts an eerie quality to his narrative. On the one hand he is often quite sure of having the answer to a particular problem (for example the gene is the unit of selection), a sort of certainty I had thought was no longer fashionable in science in general (and particularly in the domain of evolutionary studies, justly known for its authoritative imaginary tales). On the other hand, I must admit to some frustration when Ridley throws up his hands and announces that a problem still defies solution, and that, in fact, our understanding remains at the same low level attained in earlier days. It seems to me that rather more progress has been made towards resolving some of the confusion in evolutionary biology than Ridley seems willing to concede. Whence this collision between certitude and confusion? Ridley's book accurately reflects the generally unsettled state of evolutionary biology, for which, I think, David Hull is right to lay the blame on a pervasive "common sense" ontology that lies at the very core of the subject. Thus certitude stems from unexamined convictions on the very nature of such entities as genes, organisms, demes, species and taxa of higher categorical rank; and confusion ensues if we get our ontology wrong. Ridley's discussion of what species are- a stunning rerun of the Dobzhansky- Mayr position enunciated nearly 50 years ago - forms the crucial case in point. In this view, species are seen to be simul- taneously reproductive communities and fairly coherent groupings of similar organisms, recognizably distinct from other such groups. Ridley is thus forced to repeat the standard claim that species are "real" at any one time (especially well demarcated in sympatry with close relatives), but through time will, of necessity, disappear, evolving themselves out of existence as they transform into descendants. Species exist only in a single time plane, according to this view, a conceptualization that understandably outraged George Gaylord Simpson. In this received ontology, species are real, individual entities when construed as reproductive communities at any one time; they are also classes of similar organisms. Moreover, the economic adaptations of organisms (the main source of that simil- arity) are imagined to be in a constant state of overhaul, and so the properties of the members of the class change, and a species evolves itself out of existence. Ridley simply does not report that Ghiselin and Hull over a decade ago pointed out that "things" are either classes or individuals, and that there is no real trick to seeing species, if construed as reproductive com- munities, as individuals in time as well as in space. Species emerge as spatiotemporally bounded historical entities, regardless of how much, or little, adaptive modification may accrue in the phenotypes of their component organisms. Much of the doubt and confusion permeating the second half of this book stems directly from Ridley's certitude over the basic nature of species, based as it is on a rather garbled ontology. Indeed, overall the book is an excellent statement of mainstream evolutionary biology as it stands today. If it does not expose the real problem in evolutionary theory - the ontological issues - it does paint an accurate picture of the teleo- logical-ridden "who or what benefits" approach that selectionists seem ever more locked into as a source of explanation for all manner of biological phenomena. Nor is Ridley utterly conventional. Within the overall matrix of neo-Darwinian theory, he follows the Williams-Dawkins reductionism that sees the gene as the locus of evolutionary action. And, in an amusing and effective gambit that coincides well New journals review On 26 September Nature will publish the fifth annual review supplement devoted to science journals. Criteria for inclusion of a journal in the 1985 issue are that: (i) the first number appeared, or the journal was retitled, between June 1983 and May 1984 (the second cut-off date allows at least three issues of a journal to have been published, the minimum number on which a reasonable judgement can be based); (ii) it is published at least three times a year; (iii) the main language used is English. Publishers and learned societies are invited to send jour different issues of each suitable periodical, including the first and most recent numbers (if from outside the United Kingdom, by air mail) to: The Review Editor, Nature, 4 Little Essex Street, London WC2R 3LF, England. Subscription details for both 1985 and 1986 should be included. with my own prejudices, Ridley discusses systematics by contrasting phenetics and cladistics, claiming the latter is evolutionary and the former not, thereby allowing him to brush aside the vast middle ground of "evolutionary systematics" as an uninteresting muddle of the two extremes. Moreover, while Ridley is clear that cladistics does not depend upon any prior theory of how evolution actually works, in several places he makes a link between nested patterns of resemblance linking up all elements of the biota and the simple notion of descent with modification. Those nested patterns of similarity have always been the strongest evidence that life must have had an evo- lutionary history, and it is refreshing to see it acknowledged once again, just as a journalist in the United States, in a feat of literary legerdemain, has recently tried to show how cladistics somehow throws doubt on the very idea of evolution. Ridley's book is not a "fun" read. Indeed, it is difficult to determine to whom it is addressed. The style, superficially zesty (''And the prediction is this .... Here is the final result"), is actually rather flat and utterly matter-of-fact: there seems for Ridley no joy in these rather marvellous mysteries. The level is decidedly elementary - as if the intended audience were beginning students or the ever-elusive "intelligent layman" - yet the tone is so unrelentingly serious and the pace so brisk that all but the most dedicated will surely flag. Perhaps most importantly, however, the book does not get at what I think is really the matter with evolutionary theory. But as a quick yet pretty accurate summary of most of the current topics under debate, and as a source of insight about how most evolutionists still approach their topic, it should prove useful indeed. D Niles Eldredge is at the American Museum of Natural History, New York.