A framework for the integration of development and evolution: The forgotten legacy of James Meadows Rendel

The historical challenges to bridge the gaps between developmental biology and population or statistical genetics under the explanatory dominance of the Modern Evolutionary Synthesis during the 20th century have been thoroughly documented. However, although several attempts to integrate these fields have been made, most have been deemed unsuccessful. As an example of those efforts, in this paper I discuss the work of James Meadows Rendel, a student of J. B. S. Haldane and disciple of Conrad Hal Waddington. I present his largely forgotten or unrecognized, but innovative, ideas about canalization and the role of development in phylogeny as a valuable piece to connect these fields that could still have important ramifications for today's evolutionary biology. In fact, it is expected that the legacy of J. M. Rendel will be rediscovered, and more importantly, incorporated and extended by future researchers, in light of the growth of evolutionary developmental biology in the last decades. What is more, this case offers a chance to critically revisit standard historiographies about the dichotomy between developmental and population genetics research frameworks in 20th century biology.

The Degradation and Aging of Biological Systems as a Process of Information Loss and Entropy Increase

The problem of the degradation and aging of bioorganisms is herein considered from the viewpoint of statistical physics. Two typical timescales in biological systems-the time of metabolic processes and the time of the life cycle-are used. A kinetic equation describing the small timescales of the systems' characteristic processes in is proposed. Maintaining a biosystem in a time-stable state requires a constant inflow of negative entropy (negentropy). Ratios are proposed to evaluate the aging and degradation of systems in terms of entropy. As an example, the aging of the epithelium is studied. The connection of our approach to the information theory of aging is discussed, as well as theoretical constructions related to the concept of cooperon and its changing with time.

Transposable Elements: Major Players in Shaping Genomic and Evolutionary Patterns

Transposable elements (TEs) are ubiquitous genetic elements, able to jump from one location of the genome to another, in all organisms. For this reason, on the one hand, TEs can induce deleterious mutations, causing dysfunction, disease and even lethality in individuals. On the other hand, TEs can increase genetic variability, making populations better equipped to respond adaptively to environmental change. To counteract the deleterious effects of TEs, organisms have evolved strategies to avoid their activation. However, their mobilization does occur. Usually, TEs are maintained silent through several mechanisms, but they can be reactivated during certain developmental windows. Moreover, TEs can become de-repressed because of drastic changes in the external environment. Here, we describe the ‘double life’ of TEs, being both ‘parasites’ and ‘symbionts’ of the genome. We also argue that the transposition of TEs contributes to two important evolutionary processes: the temporal dynamic of evolution and the induction of genetic variability. Finally, we discuss how the interplay between two TE-dependent phenomena, insertional mutagenesis and epigenetic plasticity, plays a role in the process of evolution.