Historians tend to speak of the problem of the origin of species or the species question, as if it were a monolithic problem. In reality, the phrase refers to a, historically, surprisingly fluid and pluriform scientific issue. It has, in the course of the past five centuries, been used in no less than ten different ways or contexts. A clear taxonomy of these separate problems is useful or relevant in two ways. It certainly helps to disentangle confusions that have inevitably (...) emerged in the literature in its absence. It may, secondly, also help us to gain a more thorough understanding, or sharper view, of the history of evolutionary thought. A consequent problem-centric look at that history through the lens of various origin of species problems certainly yields intriguing results, including and particularly for our understanding of the genesis of the Wallace–Darwin theory of evolution through natural selection. (shrink)

Life appears to be a natural property of matter, but the problem of its origin only arose after early scientists refuted continuous spontaneous generation. There is no chance of life arising ‘all at once’, we need the standard scientific incremental explanation with large numbers of small steps, an approach used in both physical and evolutionary sciences. The necessity for considering both theoretical and experimental approaches is emphasized. After describing basic principles that are available (including the Darwin-Eigen cycle), the search for (...) origins is considered under four main themes. These are the RNA-world hypothesis; potential intermediates between an RNA-world and a modern world via the evolution of protein synthesis and then of DNA; possible alternatives to an RNA-world; and finally the earliest stages from the simple prebiotic systems to RNA. The triplicase/proto-ribosome theory for the origin of the ribosome is discussed where triples of nucleotides are added to a replicating RNA, with the origin of a triplet code well-before protein synthesis begins. The length of the code is suggested to arise from the early development of a ratchet mechanism that overcomes the problem of continued processivity of an RNA-based RNA-polymerase. It is probable that there were precursor stages to RNA with simpler sugars, or just two nucleotides, but we do not yet know of any better alternatives to RNA that were likely to arise naturally. For prebiotic stages (before RNA) a flow-reactor model is suggested to solve metabolism, energy gradients, and compartmentation simultaneously – thus the intense interest in some form of flow reactor. If an autocatalytic cycle could arise in such a system we would be major steps ahead. The most likely physical conditions for the origin of life require further clarification and it is still unclear whether the origin of life is more of an entropy (information) problem (and therefore high temperatures would be detrimental), rather than a kinetic problem (where high temperatures may be advantageous). (shrink)

Perhaps no term in the geological lexicon excites more passions than uniformitarianism, whose motto is “the present is the key to the past.” The term is controversial in part because it contains several meanings, which have been implicated in creating a situation of “semantic chaos” in the geological literature. Yet I argue that debates about uniformitarianism do not arise from a simple chaos of meanings. Instead, they arise from legitimate disagreements about substantive questions. This paper examines these questions and relates (...) them to several “forms of understanding” pursued by researchers in geohistory. (shrink)