The German paleontologist H. G. Bronn is best remembered for his 1860 translation and critique of Darwin's Origin of Species, and for supposedly twisting Darwinian evolution into conformity with German idealistic morphology. This analysis of Bronn's writings shows, however, that far from being mired in an outmoded idealism that confined organic change to predetermined developmental pathways, Bronn had worked throughout the 1840s and 1850s on a new, historical approach to life. He had been moving from the study of plant and (...) animal forms in the abstract towards placing them into geological and biogeographical context, analyzing patterns of progress and adaptation, explaining species diversity and individual variation, and applying biological insights to practical problems such as artificial breeding. Even though Bronn never fully accepted the idea of species transformation, he saw Darwin's theory as a bold new move toward his own goal of establishing a comprehensive, historical science of life, and he presented it as such in his translation and commentary. Thus Darwin's ideas gained a quick and generally favorable hearing in Germany not because of their easy assimilability into an older tradition, but because of their appeal to the innovative Bronn. (shrink)

We review the evidence for the concept of the “initial” or prototype brain. We outline four possible modes of brain evolution suggested by our new findings on the evolutionary status of the dolphin brain. The four modes involve various forms of deviation from and conformity to the hypothesized initial brain type. These include examples of conservative evolution, progressive evolution, and combinations of the two in which features of one or the other become dominant. The four types of neocortical organization in (...) extant mammals may be the result of selective pressures on sensory/motor systems resulting in divergent patterns of brain phylogenesis. A modular “modification/multiplication” hypothesis is proposed as a mechanism of neocortical evolution in eutherians. Representative models of the initial ancestral group of mammals include not only extant basal Insectivora but also Chiroptera; we have found that dolphins and large whales have also retained many features of the archetypal or initial brain. This group evolved from the initial mammalian stock and returned to the aquatic environment some 50 million years ago. This unique experiment of nature shows the effects of radical changes in environment on brain-body adaptations and specializations. Although the dolphin brain has certain quantitative characteristics of the evolutionary changes seen in the higher terrestrial mammals, it has also retained many of the conservative structural features of the initial brain. Its neocortical organization is accordingly different, largely in a quantitative sense, from that of terrestrial models of the initial brain such as the hedgehog. (shrink)

We review the evidence for the concept of the “initial” or prototype brain. We outline four possible modes of brain evolution suggested by our new findings on the evolutionary status of the dolphin brain. The four modes involve various forms of deviation from and conformity to the hypothesized initial brain type. These include examples of conservative evolution, progressive evolution, and combinations of the two in which features of one or the other become dominant. The four types of neocortical organization in (...) extant mammals may be the result of selective pressures on sensory/motor systems resulting in divergent patterns of brain phylogenesis. A modular “modification/multiplication” hypothesis is proposed as a mechanism of neocortical evolution in eutherians. Representative models of the initial ancestral group of mammals include not only extant basal Insectivora but also Chiroptera; we have found that dolphins and large whales have also retained many features of the archetypal or initial brain. This group evolved from the initial mammalian stock and returned to the aquatic environment some 50 million years ago. This unique experiment of nature shows the effects of radical changes in environment on brain-body adaptations and specializations. Although the dolphin brain has certain quantitative characteristics of the evolutionary changes seen in the higher terrestrial mammals, it has also retained many of the conservative structural features of the initial brain. Its neocortical organization is accordingly different, largely in a quantitative sense, from that of terrestrial models of the initial brain such as the hedgehog. (shrink)

I argue that the French sociologist Émile Durkheim (1858–1917) decided to constitute sociology, a novel field, as ‘scientific’ early in his career. He adopted evolutionized biology as then practiced as his principal model of science, but at first wavered between alternative repertoires of concepts, models, metaphors and analogies, in particular Spencerian Lamarckism and French neo-Lamarckism. I show how Durkheim came to fashion a particular deployment of the French neo-Lamarckian repertoire. The paper describes and analyzes this repertoire and explicates how it (...) might have been available to a non-biologist. I analyze Durkheim’s very early writings between 1882 and 1892 in this context to substantiate my argument. (shrink)

It is commonly accepted by those who consider macroevolution as a process decoupled from microevolution that its apparent jerkiness (and, hence, incompatibility with principles of population genetics) results from the structural complexity of epigenetic systems, since all complex cybernetic systems are expected to behave discontinuously. To analyse the validity of this assumption, the process of self-improvement has been analysed in a complex cybernetic system by means of computer simulations. It turns out that the investigated system tends to develop by accumulation (...) of as small structural changes as possible, while larger changes are likely to result in the collapse of the system rather than in its persistence or improvement. This implies that cybernetic considerations alone cannot justify the claim that the very nature of epigenetic systems induces evolution by discrete steps rather than by gradual accumulation of small changes. (shrink)

This collection of essays, written over the past fifteen years by one of the more intrepid defenders of current Darwinian theory, contains material that will be of interest both to historians and philosophers of science and, since Ruse writes well and in an accessible manner, to an even wider audience. A preliminary glance at the contents primes one to expect to be both engaged and provoked; one is not disappointed. The essays include historical speculation on some of the views of (...) Charles Darwin, a defence of human sociobiology and discussion of its feminist critique, punctuated equilibria theory, teleology in biology, extraterrestrial biology and moral theory, the plate tectonic revolution in geology, and the relationship between evolutionary theory and Christian ethics. (shrink)

There is an argument that has recently been deployed in favor of thinking that the mind is mostly (or even exclusively) composed of cognitive modules; an argument that draws from some ideas and concepts of evolutionary and of developmental biology. In a nutshell, the argument concludes that a mind that is massively composed of cognitive mechanisms that are cognitively modular (henceforth, c-modular) is more evolvable than a mind that is not c-modular (or that is scarcely c-modular), since a cognitive mechanism (...) that is c-modular is likely to be biologically modular (henceforth, b-modular), and b-modular characters are more evolvable (e.g., Sperber 2002, Carruthers 2005). In evolutionary biology, the evolvability of a character in an organism is understood as the “organism’s capacity to facilitate the generation of non-lethal selectable phenotypic variation from random mutation” with respect to that character. Here I will argue that the notion of cognitive modularity needed to make this argument plausible will have to be understood in terms of the biological notion of variational independence; that is, it will have to be understood in such a way that a cognitive feature is c-modular only if few or no other morphological changes (cognitive and not) are significantly correlated with variations of that feature arising in members of the relevant population. I will also argue that all –except for (possibly) one—of the connotations contained in a cluster of notions of cognitive modularity widely accepted in some of the mainstream currents of thought in classical cognitive science, are simply irrelevant to the argument. In order to argue for this, I will have to examine the question as to whether there are any strong theoretical connections between (1) those connotations and (2) notions of modularity accepted in biology, specially in evolutionary and in developmental biology, that are thought to be most relevant to arguments to the effect that biological modularity enhances evolvability. (shrink)

I examine an argument that has recently appeared in the cognitive science literature in favor of thinking that the mind is mostly composed of Fodorian-type cognitive modules; an argument that concludes that a mind that is massively composed of classical cognitive mechanisms that are cognitively modular is more evolvable than a mind that is not cognitively modular, since a cognitive mechanism that is cognitively modular is likely to be biologically modular, and biologically modular characters are more evolvable. I argue that (...) the notion of cognitive modularity needed to make this argument plausible will have to be understood in terms of the biological notion of variational independence, as follows: a cognitive feature is cognitively modular only if few or no other morphological changes are significantly correlated with variations of that feature arising in members of the relevant population as a result of ontogeny. I also argue that most of the connotations contained in a cluster of notions of classical cognitive modularity are, as far as we know, irrelevant to the argument, and that only the presence of selective impairments—also known as cognitive dissociations—can be considered as strong indicators of the type of modularity that genuinely enhances evolvability. (shrink)

Historiographical accounts typically place the formulation of the first embryological theory of the evolutionary origin of vertebrates after the publication of Darwin’s On the Origin of Species. However, the French naturalist Étienne Geoffroy Saint-Hilaire developed an embryological evolutionary model in the 1820s that followed the Lamarckian theory. Geoffroy was the first to establish a direct embryological relationship between vertebrates and invertebrates. This idea was not forgotten, and the embryologists Anton Dohrn and Carl Semper subsequently updated it in their annelid theory (...) as part of a debate about the origin of vertebrates that occurred during the latter part of the nineteenth century. This paper reviews the traditional historiography, analyzing and integrating Geoffroy’s model into the current body of ideas. (shrink)

Both autonomy and local specificity are compatible with observed interconnectivity at the cell level when considering two different levels: cell assemblies and brain systems. Early syntactic structuring processes in particular are likely to representan autonomous module in the language/brain system.

This paper has three principal aims: first, through a detailed analysis of the hypotheses and assumptions underlying Weismann’s and Morgan’s disagreement on the nature of animal regeneration, it seeks to readdress the imbalance in coverage of their discussion, providing, at the same time, a fascinating case-study for those interested in general issues related to controversies in science. Second, contrary to Morgan’s beliefs according to which Weismann employed a speculative and unempirical method of scientific investigation, the article shows that Weismann performed (...) experiments, made observations and proposed ‘undogmatic’ theories open to refutation. Third, through the reconstruction of Weismann’s and Morgan’s disagreement, this study illustrates how biology, during the very late nineteenth and early twentieth centuries, was undergoing important changes. I argue that this controversy clearly and convincingly demonstrates how some important epistemic assumptions became increasingly problematic for some members of the younger generations of biologists. At the end of my discussion I will also argue that Weismann and Morgan both had strong well-grounded arguments supporting their conclusions; for this reason I suggest a few factors (“taken-for-granted” beliefs or assumptions) that could explain why their disagreement was doomed to remain unresolved. In particular, I will analyze their diverse explicative interests, their different theoretical concerns and their distinct use of the available evidence. (shrink)

At the beginning of the twentieth century Haeckel’s biogenetic law was widely questioned. On the one hand, there were those who wanted to dismiss it altogether: ontogeny and phylogeny did not have any systematic or interesting relation. On the other hand, there were those who sought to revise it. They argued that while Haeckel’s recapitulationism might have been erroneous, this should not deter the research over the relation between evolution and development. The British embryologist Walter Garstang was one of the (...) main figures on the “revisionists” side. In this paper, I first situate Garstang’s contribution to embryology and evolution within the extraordinarily creative period of the first three decades of the twentieth century. Then, I review some of Garstang’s specific ideas in detail, especially his most well-known 1922 paper “The Theory of Recapitulation.” Finally, I look at how the demise of the biogenetic law in light of Garstang’s views—as well as from the perspective of contemporary developmental evolution—should be understood. My main concern is not about the dismissal of Haeckel’s law or the sidelining of embryology in the twentieth-century evolutionary biology. I am rather interested in exploring why Garstang’s revised version of biogenetic law—which was entirely consistent with the neo-Darwinian perspective underpinning the Modern synthesis—did not spur a major new agenda in evolutionary biology after the 1930s. (shrink)

Have the large-scale evolutionary patterns illustrated by the fossil record been driven by fluctuations in environmental opportunity, by biotic factors, or by changes in the types of phenotypic variants available for evolutionary change? Since the Modern Synthesis most evolutionary biologists have maintained that microevolutionary processes carrying on over sufficient time will generate macroevolutionary patterns, with no need for other pattern-generating mechanisms such as punctuated equilibrium or species selection. This view was challenged by paleontologists in the 1970s with proposals that the (...) differential sorting and selection of species and clades, and the effects of biotic crises such as mass extinctions, were important extensions to traditional evolutionary theory. More recently those interested in macroevolution have debated the relative importance of abiotic and biotic factors in driving macroevolutionary patterns and have introduced comparative phylogenetic methods to analyze the rates of change in taxonomic diversity. Applying Peter Godfrey-Smith’s distinction between distributional explanations and explanations focusing on the origin of variation, most macroevolutionary studies have provided distributional explanations of macroevolutionary patterns. Comparative studies of developmental evolution, however, have implicated the origin of variants as a driving macroevolution force. In particular, the repatterning of gene regulatory networks provides new insights into the origins of developmental novelties. This raises the question of whether macroevolution has been pulled by the generation of environmental opportunity, or pushed by the introduction of new morphologies. The contrast between distributional and origination scenarios has implications for understanding evolutionary novelty and innovation and how macroevolutionary process may have evolved over time. (shrink)

The C. elegans male tail is being studied as a model to understand how genes specify the form of multicellular animals. Morphogenesis of the specialized male copulatory organ takes place in the last larval stages during male development. Genetic analysis is facilitated because the structure is not necessary for male viability or for strain propagation. Analysis of developmental mutants, isolated in several functional and morphological screens, has begun to reveal how fates of cells are determined in the cell lineages, and (...) how the specification of cell fates affects the morphology of the structure. Cytological studies in wild type and in mutants have been used to study the mechanism of pattern formation in the tail peripheral nervous system. The ultimate goal is to define the entire pathway leading to the male copulatory organ. (shrink)

In the present paper I develop a model of the evolutionary process associated to the widespread although controversial notion of a prevailing trend of increasing complexity over time. The model builds on a coupling of evolution to individual developmental programs and introduces an integrated view of evolution implying that human culture and science form a continuous extension of organic evolution. It is formed as a mathematical model that has made possible a quantitative estimation in relative terms of the growth of (...) complexity. This estimation is accomplished by means of computer simulations the result of which indicates a strong acceleration of complexity all the way from the appearance of multicellular organisms up to modern man. (shrink)