An adaptationist programme has dominated evolutionary thought in England and the United States during the past 40 years. It is based on faith in the power of natural selection as an optimizing agent. It proceeds by breaking an organism into unitary ‘traits’ and proposing an adaptive story for each considered separately. Trade-offs among competing selective demands exert the only brake upon perfection; non-optimality is thereby rendered as a result of adaptation as well. We criticize this approach and attempt to reassert a competing notion (long popular in continental Europe) that organisms must be analysed as integrated wholes, with Baupläne so constrained by phyletic heritage, pathways of development and general architecture that the constraints themselves become more interesting and more important in delimiting pathways of change than the selective force that may mediate change when it occurs. We fault the adaptationist programme for its failure to distinguish current utility from reasons for origin (male tyrannosaurs may have used their diminutive front legs to titillate female partners, but this will not explain why they got so small); for its unwillingness to consider alternatives to adaptive stories; for its reliance upon plausibility alone as a criterion for accepting speculative tales; and for its failure to consider adequately such competing themes as random fixation of alleles, production of non-adaptive structures by developmental correlation with selected features (allometry, pleiotropy, material compensation, mechanically forced correlation), the separability of adaptation and selection, multiple adaptive peaks, and current utility as an epiphenomenon of non-adaptive structures. We support Darwin’s own pluralistic approach to identifying the agents of evolutionary change.

The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme

An adaptationist programme has dominated evolutionary thought in England and the United States during the past 40 years. It is based on faith in the power of natural selection as an optimizing agent. It proceeds by breaking an organism into unitary 'traits' and proposing an adaptive story for each considered separately. Trade-offs among competing selective demands exert the onlv brake upon perfection; non-optimality is thereby rendered as a result of adaptation as well. We criticize this approach and attempt to reassert a competing notion (long popular in continental Europe) that organisms must be analysed as integrated wholes, with Bauplane so constrained by phyletic heritage, pathways of development and general architecture that the constraints themselves become more interesting and more important in delimiting pathways of change than the selective force that may mediate change when it occurs. We fault the adaptationist programme for its failure to distinguish current utility from reasons for origin (male tyrannosaurs may have used their diminutive front legs to titillate female partners, but this will not explain why they got so small); for its unwillingness to consider alternatives to adaptive stories; for its reliance upon plausibility alone as a criterion for accepting speculative tales; and for its failure to consider adequately such competing themes as random fixation of alleles, production of nonadaptive structures by developmental correlation with selected features (allometry, pleiotropy, material compensation, mechanically forced correlation), the separability of adaptation and selection, multiple adaptive peaks, and current utility as an epiphenomenon of non-adaptive structures. We support Darwin's own pluralistic approach to identifying the agents of evolutionary change.

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Adaptation has been defined and recognized by two different criteria: historical genesis (fea- tures built by natural selection for their present role) and current utility (features now enhancing fitness no matter how they arose). Biologists have often failed to recognize the potential confusion between these different definitions because we have tended to view natural selection as so dominant among evolutionary mechanisms that historical process and current product become one. Yet if many features of organisms are non-adapted, but available for useful cooptation in descendants, then an important concept has no name in our lexicon (and unnamed ideas generally remain unconsidered): features that now enhance fitness but were not built by natural selection for their current role. We propose that such features be called exaptations and that adaptation be restricted, as Darwin suggested, to features built by selection for their current role. We present several examples of exaptation, indicating where a failure to concep- tualize such an idea limited the range of hypotheses previously available. We explore several consequences of exaptation and propose a terminological solution to the problem of preadaptation.

Exaptation; a missing term in the science of form

I. the origin of species by means of natural selection

In the last two decades, the widespread application of genetic and genomic approaches has revealed a bacterial world astonishing in its ubiquity and diversity. This review examines how a growing knowledge of the vast range of animal–bacterial interactions, whether in shared ecosystems or intimate symbioses, is fundamentally altering our understanding of animal biology. Specifically, we highlight recent technological and intellectual advances that have changed our thinking about five questions: how have bacteria facilitated the origin and evolution of animals; how do animals and bacteria affect each other’s genomes; how does normal animal development depend on bacterial partners; how is homeostasis maintained between animals and their symbionts; and how can ecological approaches deepen our understanding of the multiple levels of animal–bacterial interaction. As answers to these fundamental questions emerge, all biologists will be challenged to broaden their appreciation of these interactions and to include investigations of the relationships between and among bacteria and their animal partners as we seek a better understanding of the natural world.

/pdf/animals-in-a-bacterial-world-a-new-imperative-for-the-life-114xzos8tm.pdf

Animals in a bacterial world, a new imperative for the life sciences

This book reviews and discusses the most up-to-date knowledge in the fields of cyclostratigraphy and event stratigraphy The book contains 48 papers contributed by the most knowledgeable geologists and paleontologists in the fields of cycle and event stratigraphy It is divided into two parts Part one is concerned with the structure of individual beds and larger cycles and sequences and discusses; rhythmic stratification, event stratification, diagenetic overprint, cherts and phosphorites, and preservation and biologic destruction of laminated sediments Part two, on larger cycles and sequences, looks at sequences, hierarchies, causes and environmental expression, and timing and correlation, ie the cycles of frequencies from millions of years to thousands of years (Milankovich band) Summaries on spectral analysis are also presented There are 80 pages of references and a comprehensive index It is extensively illustrated with line drawings and graphs Practicing sedimentary geologists without access to a good library or find it hard to keep up with the plethora of journal articles and want a refresher in this area of stratigraphy will find the book particularly useful

Cycles and events in stratigraphy

Bathymetry of trace fossils

Vertebrate Tracks.- Arthropod Trackways.- Trilobite Burrows.- Arthropod Tunnel Systems.- Resting Traces.- Burrows of Short Bulldozers.- Burrows of Wormlike Bulldozers.- Burrows of Stripminers.- Arthrophycid Burrows.- Probers.- Deepsea Farmers.- Pseudo-Traces.- Earliest Trace Fossils.- Cruziana Stratigraphy.- Ichnofacies.

Trace Fossil Analysis

The strange biota of Neoproterozoic sea bottoms become more understandable if we assume that otherwise soft sediments were sealed by firm and erosion-resistant biomats. This allowed "mat encrusters" (vendobionts; trilobozoan and other sponges) to get attached to sandy bottoms, and molluscan "mat scratchers" to scrape off an algal film, as if they were living on rocks. Minute conical "mat stickers" (Cloudina) probably required a sticky substrate to become stabilized in upright position. Horizontal burrows are interpreted as the works of worm-like "undermat miners." Only the latter lifestyle appears to go back to the Mesoproterozoic; the others emerged in Vendian times and virtually disappeared when matgrounds became restricted to hostile environments in the wake of the Cambrian ecological revolution.

Biomat-related lifestyles in the Precambrian

SUMMARY

Fault grading is expressed by a regular structural sequence of (from top) liquified zone, rubble zone and step-faulted zone, with gradational contacts between these zones and the bottom, but with a sharp boundary at the top. It is interpreted as an effect of strong earthquakes on gradationally compacted muds in quiet water basins. Fault-graded beds are geopetal and paleoslope criteria. If interpreted as seismites they may also be used as paleo-seismograms.

Adolf Seilacher

Papers

Cycles and events in stratigraphy

Bathymetry of trace fossils

Trace Fossil Analysis

Biomat-related lifestyles in the Precambrian

Fault‐graded beds interpreted as seismites