August Weismann rejected the inheritance of acquired characters on the grounds that changes to the soma cannot produce the kind of changes to the germ-plasm that would result in the altered character being transmitted to subsequent generations. His intended distinction, between germ-plasm and soma, was closer to the modern distinction between genotype and phenotype than to the modern distinction between germ cells and somatic cells. Recently, systems of epigenetic inheritance have been claimed to make possible the inheritance of acquired characters. (...) I argue that the sense in which these claims are true does not challenge fundamental tenets of neo-Darwinism. Epigenetic inheritance expands the range of options available to genes but evolutionary adaptation remains the product of natural selection of ‘random’ variation. (shrink)

The CRISPR-Cas systems of bacterial and archaeal adaptive immunity have become a household name among biologists and even the general public thanks to the unprecedented success of the new generation of genome editing tools utilizing Cas proteins. However, the fundamental biological features of CRISPR-Cas are of no lesser interest and have major impacts on our understanding of the evolution of antivirus defense, host-parasite coevolution, self versus non-self discrimination and mechanisms of adaptation. CRISPR-Cas systems present the best known case in point (...) for Lamarckian evolution, i.e. generation of heritable, adaptive genomic changes in response to encounters with external factors, in this case, foreign nucleic acids. CRISPR-Cas systems employ multiple mechanisms of self versus non-self discrimination but, as is the case with immune systems in general, are nevertheless costly because autoimmunity cannot be eliminated completely. In addition to the autoimmunity, the fitness cost of CRISPR-Cas systems appears to be determined by their inhibitory effect on horizontal gene transfer, curtailing evolutionary innovation. Hence the dynamic evolution of CRISPR-Cas loci that are frequently lost and acquired by archaea and bacteria. Another fundamental biological feature of CRISPR-Cas is its intimate connection with programmed cell death and dormancy induction in microbes. In this and, possibly, other immune systems, active immune response appears to be coupled to a different form of defense, namely, “altruistic” shutdown of cellular functions resulting in protection of neighboring cells. Finally, analysis of the evolutionary connections of Cas proteins reveals multiple contributions of mobile genetic elements to the origin of various components of CRISPR-Cas systems, furthermore, different biological systems that function by genome manipulation appear to have evolved convergently from unrelated MGE. The shared features of adaptive defense systems and MGE, namely the ability to recognize and cleave unique sites in genomes, make them ideal candidates for genome editing and engineering tools. (shrink)

Scientific pluralism is an issue at the forefront of philosophy of science. This landmark work addresses the question, Can pluralism be advanced as a general, philosophical interpretation of science? Scientific Pluralism demonstrates the viability of the view that some phenomena require multiple accounts. Pluralists observe that scientists present various—sometimes even incompatible—models of the world and argue that this is due to the complexity of the world and representational limitations. Including investigations in biology, physics, economics, psychology, and mathematics, this work provides (...) an empirical basis for a consistent stance on pluralism and makes the case that it should change the ways that philosophers, historians, and social scientists analyze scientific knowledge. Contributors: John Bell, U of Western Ontario; Michael Dickson, U of South Carolina; Carla Fehr, Iowa State U; Ronald N. Giere, U of Minnesota; Geoffrey Hellman, U of Minnesota; Alan Richardson, U of British Columbia; C. Wade Savage, U of Minnesota; Esther-Mirjam Sent, U of Nijmegen. Stephen H. Kellert is professor of philosophy at Hamline University and a fellow of the Minnesota Center for Philosophy of Science. Helen E. Longino is professor of philosophy at Stanford University. C. Kenneth Waters is associate professor of philosophy and director of the Minnesota Center for Philosophy of Science. (shrink)