Knowing how introns originated should greatly enhance our understanding of the information we carry in our DNA. Gilbert’s suggestion that introns initially arose to facilitate recombination still stands, though not for the reason he gave. Reanney’s alternative, that evolution, from the early “RNA world” to today’s DNA-based world, would require the ability to detect and correct errors by recombination, now seems more likely. Consistent with this, introns are richer than exons in the potential to extrude the stem-loop structures needed for (...) the homology search that can lead to heteroduplex formation and the recognition of base mismatches. In nucleic acid sequences that were unable concomitantly to encode sufficient stem-loop potential, protein-encoding potential was constrained to arise as segments (exons) interrupted by segments rich in stem-loop potential (introns). Thus, sequences with properties that we now deem intronic are likely to have preceded the emergence of exons. (shrink)

Eminent scientists are well-placed to bring the novel works of others, even if not in their own areas of expertise, to general attention. In so doing, they may be able to extend original accounts or introduce new terminologies, but they are basically messengers, not innovators. In the 1940s an evolutionary theory of biological aging was explained by Peter Medawar, and informational concepts relating to DNA were explained by Erwin Schrödinger. Both explanations were eventually traced back to the Victorian polymath Samuel (...) Butler—one by Medawar’s research associate Alex Comfort, and the other, albeit indirectly, by Schrödinger himself. In his time Butler’s works were too erudite for general readers and too laden with populist jargon for contemporary experts to take seriously. However, today it appears counterfactually plausible that an early acceptance of his ideas would have greatly quickened the pace of research. (shrink)

The theory of evolution by natural selection is, perhaps, the crowning intellectual achievement of the biological sciences. There is, however, considerable debate about which entity or entities are selected and what it is that fits them for that role. This article aims to clarify what is at issue in these debates by identifying four distinct, though often confused, concerns and then identifying how the debates on what constitute the units of selection depend to a significant degree on which of these (...) four questions a thinker regards as central. (shrink)