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Every research scientist at some time yearns to get something, anything, published in the prestigious British journal, Nature. A Nature paper is a shining medallion to be worn with pride, bestowing on the owner an aura of esteem in the tea-rooms and corridors of scientific establishments world-wide. You've probably met a few scientists who, once they have a half-baked idea, the eyes glaze over, the light bulb appears above the head, and they mutter to themselves "I think there's a Nature paper in it!" Some scientific institutions have been known to sink big dollars into research infrastructure on the half chance of getting a string of "stuff" into Nature. Unlike many other publication vehicles it is rapid, sharp, contemporary, trendy and often provocative. It is considered by many to be the Rolls Royce of scientific publishing.

As an article in Nature is a much sought after addition to everybody's publication list, the editors are obviously deluged by a huge volume of flashes of inspiration, of variable quality, from across the scientific globe. As there are only a finite number of "cutting-edge" ideas the most adventurous editor can squeeze into the one issue, this must lead to a massive haemorrhaging in the quantity of rejections. Although we have no first hand experience of this, we hear that politeness in the review process can evaporate with the high rejection rate. How would you like a review notice that started - "When I read the title of the paper I thought I'd be reading something interesting....", and then proceeded to be even less flattering? You'd need a thick hide and a massive ego to survive this treatment unscathed and still eagerly inflict your every insight, no matter how meagre, on an editorial office bursting at the seams. Others who are not protected by a massive ego console themselves in the face of rejection with the notion that there is a fair element of luck involved; for a Nature publication the topic has to be "trendy" or "hot" to make it into print. This is something that the editor Henry Gee readily admits in his introductory notes.

This book, "Shaking the Tree", is a collection of invited essays on the "hot" topics concerning the stuff of life. The contributors to this volume are the scientific superstars who, through the quality of their insights and communication skills, have in some sense gone "beyond the review process". Their wisdom is actively sought by the overloaded editor. They are the high priests and priestesses of biology and palaeontology. The essays, all taken from the pages of Nature, present a series of "state of the art" reports for the period 1991 - 1997. They are grouped together like genes on a chromosome, under broad themes and purport to represent the latest word on a range of topics concerning the nature and history of life.

Each group of essays is stitched together with some general introductory comments by Gee to set the scene. If the scientific arena is analogous to the sports field, then Gee provides the expert commentary. He has all the necessary attributes, an encyclopaedic knowledge of the players, their history in earlier encounters, the rules of the game and most importantly an obvious enthusiasm for the subject matter. As the name of the volume suggests, many of the contributions are more than just straight reviews, most deal with paradigm shifts, continuing debate and unresolved conflict in recent research. Many of the better articles in the collection are those that ponder the gulf between the interpretations of modern molecular bioscience and morphological studies from the fossil record and either attempt some form of reconciliation in their synthesis or suggest further investigations as a focus for possible future resolution.

The first group of essays deals with how the branches of the tree of life are related to each other. Twenty-one years after their first publication on punctuated equilibrium, Stephen Jay Gould and Niles Eldredge visit the same intellectual territory to see how the landscape has changed, in an offering that Gee describes as "understandably self-indulgent". They find much to their liking and proclaim that their theory has come of age as a paradigm shift in the best traditions of Thomas Kuhn, both by homology and analogy. Szathmary and Maynard Smith follow by examining some of the major forks in the tree; prokaryotes to eukaryotes, protists to metazoans and many others (strangely the Archaea don't even rate a mention!), in terms of the adaptive value of increased complexity. They provide some biochemical insights and speculation about these major changes. This first group concludes with Caro-Beth Stewart's clearly written explanation of parsimony analysis including candid discussion of its effectiveness and inadequacies. It is all context that counts! How is the investigation framed? As such it includes the cheery advice to ignore certain data when appropriate. Heaven forbid, should such a practice become common place in science! This reminded us of a famous North American palaeontologist on field-work in remote north Queensland 5 years ago who provided one of the best unwritten statements on the scientific process. "Science is all about gathering your data set and then bullshiting your way through the anomalies".

The focus for the second group of essays is Geoffrey St Hillare's classic insight that structurally, arthropods appear to be inverted chordates. If not for the fact that this realisation struck the celebrated naturalist some 47 years before the first issue of Nature, you can visualise his laboratory at the National Natural History Museum in Paris, lobster innards splayed across the dissecting table, and Geoffrey saying to himself, "I think there's a Nature paper in it!" The roles that the incredibly versatile hox cluster of genes, shared by almost all multicellular animals, play in the development of form and function of body bits across phyla are investigated in the essays that follow. Sean Carroll discusses the natural history and behaviour of hox genes in vertebrates and arthropods in pondering Geoffrey's insight. Next time you're contemplating the dissection of a lobster thermidore, its sobering to realise that if it were not for genetic regulation in the hox department your dorsal side could have been ventralised and the roles reversed in more ways than one. De Robertis and Sasai are also transfixed by the dorso-ventral axis and speculate on the nature of the ancestor of arthropods and chordates and consider the possibility of segmentation of this Urbilateria. Neil Shubin and coworkers offer an essay on appendages; the fins, wings, and limbs of arthropods and chordates and the control of a similar genetic regulatory system in all of these. The transitions from one to another as gleaned from the fossil record is explored in terms of regulatory changes that may explain such phenomena as the contemporaneous nature of carpal and tarsal digitation. The final offering is an invitation to a game of metazoan phylogeny by Simon Conway Morris. Gee describes him as having one of the most fearless imaginations in palaeontology, an attribute derived in part from his work on the bizarre components of the Burgess Shale fauna such as Hallucigenia. Alas, even this creature has lost its mystique and is unveiled as a humble Cambrian velvet worm. The template for Conway Morris's game of metazoan phylogeny is the diploblasic ediacarans and the triploblastic Cambrian groups that followed. Within that simple framework of early metazoans every manner of radiata, bilateria, platymorpha, dueterostoma and protostoma are considered at a breathtaking pace. As he notes at the start, the only game ever attempted has lasted a billion years and shows no sign of a conclusion.

The next section is entitled "Seeing the tree for the woods" and the focus here is the global context; as the topic is environmental change through time, this section is probably of most interest to those with an earth science background. Andrew Knoll and Malcolm Walter open the batting with one of the most lucid pieces on stratigraphy that we've found in recent years. This essay conveys a sense of the excitement of constructing a pioneering chronostratigraphy as they explore the promise and frustration of attempting to slice up the latest Proterozoic, or the Earth's "Old Testament", a time of intense biogeochemical, climatic and tectonic change. They cover ediacarans, fossil protists and prokaryotes, stromatolites, ice ages, sequence stratigraphy, strontium and carbon isotopes, zircons and much more. They conclude that the way forward is through microfossils and stable isotopes. Although some 8 years old, this essay should be mandatory reading in any stratigraphy course for the insights it gives about the process. William Shear ponders the development of the first terrestrial ecosystems in the next essay. It stresses the difficulties in drawing analogies between modern and Palaeozoic ecosystems. Algae, lichens and cyanobacteria and possibly plants unlike any modern representatives, lived with carnivores and detritivores before any early animal communities included herbivores. This is the oldest essay in the book (1991), as such it presents a view of ecosystem modernisation occurring in the Devonian. He considers the Upper Silurian age of Australia's "Baragwanathia" as a bit dubious, but recent biostratigraphic analysis by Barrie Rickards has confirmed the Upper Silurian (Pridoli) age for the Baragwanathia-bearing beds. He finishes with some notes on the ecological context of the Late Palaeozoic rise to prominence of insects and tetrapods (yes those two inverted groups again) with monster Carboniferous dragon-flies engaged in a size-based arms race. Douglas Erwin searches for multiple causes of the Permo-Triassic extinction in the final essay in this cluster. The immensity and causal complexity of this extinction event has somewhat been overlooked, as bolide impacts and big animals expiring on mass in one particular much younger event, has captured the public imagination. It is clear, however, that a single villain can not be 'fingered' at the close of the Palaeozoic.

The next section considers case histories in phylogeny. It is the largest group in the book and gives it the title. Seven contributions cover a vast span of biological information, theory and speculation. Paul Kendrick and Peter Crane return to the middle Palaeozoic to review the early history of land plants in what Gee describes as a natural extension of Shear's paper. This essay is only three years old and includes molecular data in discussing relationships between groups. There is no controversy concerning the age of Baragwanathia here. They conclude that many major lineages of land plants existed by the mid Silurian and the poor megafossil record is related to significant regressive cycles. Crane joins Friis and Pedersen to consider the origin and early diversification of angiosperms. Molecular evidence suggests a long cryptic history of angiosperm evolution. This is contrary to the lack of distinctive triaperturate pollen grains in the pre-Cretaceous fossil record. This time the authors argue that the fossil record is close to the true account, and support this by noting that after the magnolias there is an ordered sequential appearance of angiosperm families throughout the Cretaceous. Peter Forey and Phillipe Janvier rattle through a catalogue of recent fossil finds, including Arandaspis from the Lower Ordovician of Australia, in considering the origin of jawed vertebrates. These have inspired vigorous debate on the relationships between the earliest vertebrate groups often sharply dividing palaeontologists and biologists. These recent discoveries include the conodont animal that may push the date of the earliest vertebrates back further in time. They conclude there is still plenty of scope for new work on old fish. Per Ahlberg and Andrew Miller outline the development of ideas concerning tetrapod origins based in the early days on poor fossil evidence and geological inferences from the Devonian red beds, through to debates on monophyly and the impact of cladistics. The latter is undoubtedly a powerful tool for unravelling the sequence of character acquisition that aided the vertebrate invasion of land, but they express slight surprise that some pre-cladistic models have proved rather robust. They review some stem tetrapod groups and conclude that once suitable intermediaries have been theoretically constructed, it is necessary to go out and find the fossils. We suppose its good to know what you're looking for before venturing into the field! Luis Chiappe puts avian evolution under the microscope starting with Archaeopteryx. Contemplating the gap between this and the diverse inhabitants of the Cretaceous gives the essay its title. It appears that despite many recent fossil finds, early avian history is still cryptic. Apart from the revelation that avian phylogeny is "nested" in therapod origins there appears to be little agreement on much else. The final work in this group, Michael Novocek's essay on mammal phylogeny was the inspiration for the book. Simpson's classic 1945 classification of mammals is scrutinised in light of a whole array of new data. The four line abstract sums up the gist of the article, and in fact the whole book. It can be summarised as even though morphological and molecular data provide fresh insights into mammal phylogeny, many questions remain unresolved. Gene sequence data, immunological comparisons, protein sequencing, morphological and palaeontologic data all appear to have areas of congruence and conflict - such is the nature of science!

In an anthropocentric gesture, the final part of the book ventures out along one particular, very familiar, limb. These essays are entitled "climbing down", presumably in reference to the descent of humankind, and deal with primate evolution. Robert Martin investigates the origin of primates and indicates that the poor nature of the fossil record continually leads to underestimation in the timing of splits from basal groups, a fact that Gee notes is not limited to primates. Martin concludes that the origin of simian primates could be pushed back as far as the Paleocene. The same problems plague consensus in understanding the evolution of our own family, the Hominoidea. Peter Andrews discusses some of the possibilities, but with a poor fossil record prior to 5 million years ago, and the lack of a fossil record for African apes, much must remain conjectural. Bernard Wood completes the collection by looking at the origins of our genus, Homo. Despite advances in absolute dating techniques and reinterpretation of the known fossil evidence, no simple model fits the bill. Gee notes the ultimate anthropocentrism, in that a review of the origin of our species was not possible as this topic has carried a level of acrimony that is even beyond the load capacity of a Nature editor. By this stage we are left staring at a single leaf on the "shaking" tree.

While all the ideas presented in this book will not stand the test of time, it provides an excellent snapshot of biological thought at the cusp of the millennium. For those who enjoy the consumption of natural history literature, this is a thumping good read. All of the figures are reproduced in black and white, but in an innovative approach, the original colour version of each figure is also available direct from the web for the interested reader. The book also provides with a comprehensive subject index.

We were somewhat aghast at the recommended retail price for this book and initially thought that it may have mistakenly carried the hard cover price. Alas not so! When you consider, however, the value of an eight-year subscription to the journal, plus the convenience of having someone pick and intelligently package what we consider to be the choicest fruit from the "tree" of Nature, we must reluctantly agree that it represents good value for money. Nevertheless, our thanks to the publishers for the review copy are sincere. All in all, this book is a highly accessible, engaging and illuminating collection of works, a real "page-turner". It is a must for the bookshelves of everyone with more than a passing interest in palaeobiology.

This article was originally published in The Australian Geologist 116, 42-44.

Andrew Simpson
Division of Environmental and Life Sciences
Macquarie University, NSW 2109

Glenn A. Brock
Centre for Ecostratigraphy & Palaeobiology
Department of Earth & Planetary Sciences
Macquarie University, NSW 2109