The theory of evolution, which provides the conceptual framework for all modern research in organismal biology and informs research in molecular bi- ology, has gone through several stages of expansion and refinement. Darwin and Wallace (1858) of course proposed the original idea, centering on the twin concepts of natural selection and common descent. Shortly thereafter, Wallace and August Weismann worked toward the complete elimination of any Lamarckian vestiges from the theory, leaning in particular on Weismann’s (1893) concept of the separation (...) of soma and germ, resulting in what is some- times referred to as “neo-Darwinism”. (shrink)

The idea of genetic assimilation, that environmentally induced phenotypes may become genetically fixed and no longer require the original environmental stimulus, has had varied success through time in evolutionary biology research. Proposed by Waddington in the 1940s, it became an area of active empirical research mostly thanks to the efforts of its inventor and his collaborators. It was then attacked as of minor importance during the ‘‘hardening’’ of the neo-Darwinian synthesis and was relegated to a secondary role for decades. Recently, (...) several papers have appeared, mostly independently of each other, to explore the likelihood of genetic assimilation as a biological phenomenon and its potential importance to our understanding of evolution. In this article we briefly trace the history of the concept and then discuss theoretical models that have newly employed genetic assimilation in a variety of contexts. We propose a typical scenario of evolution of genetic assimilation via an intermediate stage of phenotypic plasticity and present potential examples of the same. We also discuss a conceptual map of current and future lines of research aimed at exploring the actual relevance of genetic assimilation for evolutionary biology. (shrink)

The biologist Mary Jane West-Eberhard publishes, in 2003, a book, entitled Developmental Plasticity and Evolution, in which a new synthetic approach, integrating development with evolution, is offered. For this reason, the book is seen as a piece of work in the field of Evolutionary developmental biology, commonly known as Evo Devo, whose aim is to synthesize data from both development and evolution. However, West-Eberhard's ambition is much higher in this book because she does not only focus on gathering the data (...) from both fields, but she also wants to formalize a new synthetic theory of evolution, which includes development in its definition. She also explains that, in order to provide such a synthetic theory of evolution, she needs to offer an "inclusive definition of plasticity" in order to avoid "unnecessary distinctions at every turn" even if she assumes that such distinctions may be important for certain points. Our aim, in this article, is to explore the implications and consequences of West-Eberhard's "inclusive definition of plasticity" in such an attempt of a new synthesis of evolutionary theory, including development. (shrink)

A standard norm of reaction (NoR) is a graphical depiction of the phenotypic value of some trait of an individual genotype in a population as a function of an environmental parameter. NoRs thus depict the phenotypic plasticity of a trait. The topological properties of NoRs for sets of different genotypes can be used to infer the presence of (non-linear) genotype-environment interactions. While it is clear that many NoRs are adaptive, it is not yet settled whether their evolutionary etiology should be (...) explained by selection on the mean phenotypic trait values in different environments or whether there are specific genes conferring plasticity. If the second alternative is true the NoR is itself an object of selection. Generalized NoRs depict plasticity at the level of populations or subspecies within a species, species within a genus, or taxa at higher levels. Historically, generalized NoRs have routinely been drawn though rarely explicitly recognized as such. Such generalized NoRs can be used to make evolutionary inferences at higher taxonomic levels in a way analagous to how standard NoRs are used for microevolutionary inferences. (shrink)