Evolutionary analyses of non-genealogical bonds produced by introgressive descent

All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity

The metaphysics of the disunified world.

Pluralism is usually opposed to realism. That's why realists tend to affirm reductionism, even if only the lapsed reductionism of supervenience. It is no accident that postmoderns talk about the different worlds we live in. The realist is bent upon one world with one history, and that is the history for the sciences to tell about it, albeit with different degrees of precision, for different purposes and different points of view. The opposition between realism and pluralism is multiplied when the domains of different theories float about as in the balloon image of the relation of the sciences (Figure 1) and when no combination of fields can together supply a set of descriptions in terms of which at least one baseline history can be told. But the opposition is not necessary.</jats:p

Genes in the postgenomic era

We outline three very different concepts of the gene - 'instrumental', 'nominal', and 'postgenomic'. The instrumental gene has a critical role in the construction and interpretation of experiments in which the relationship between genotype and phenotype is explored via hybridization between organisms or directly between nucleic acid molecules. It also plays an important theoretical role in the foundations of disciplines such as quantitative genetics and population genetics. The nominal gene is a critical practical tool, allowing stable communication between bioscientists in a wide range of fields grounded in well-defined sequences of nucleotides, but this concept does not embody major theoretical insights into genome structure or function. The post-genomic gene embodies the continuing project of understanding how genome structure supports genome function, but with a deflationary picture of the gene as a structural unit. This final concept of the gene poses a significant challenge to conventional assumptions about the relationship between genome structure and function, and between genotype and phenotype

On microRNA and the Need for Exploratory Experimentation in Post-Genomic Molecular Biology

This paper is devoted to an examination of the discovery, characterization, and analysis of the functions of microRNAs, which also serves as a vehicle for demonstrating the importance of exploratory experimentation in current (post-genomic) molecular biology. The material on microRNAs is important in its own right: it provides important insight into the extreme complexity of regulatory networks involving components made of DNA, RNA, and protein. These networks play a central role in regulating development of multicellular organisms and illustrate the importance of epigenetic as well as genetic systems in evolution and development. The examination of these matters yields principled arguments for the historicity of the functions of key biological molecules and for the indispensability of exploratory experimentation in contemporary molecular biology as well as some insight into the complex interplay between exploratory experimentation and hypothesis-driven science. This latter result is not only of importance for philosophy of science, but also of practical importance for the evaluation of grant proposals, although the elaboration of this latter claim must be left for another occasion