Origins of Life, Biodiversity & Popper´s deductive cycle.
From the Book "Origins of Life":
Fig. 11.1 in:
Lankenau, D.-H. 2011. Two RNA Worlds: Toward the Origin of Replication, Genes, Recombination and Repair, p. 225-286. In R. Egel, D.-H. Lankenau, and A. Y. Mulkidjanian (ed.), Origins of Life: The Primal Self-Organization. Springer Verlag, Heidelberg.
Figure legend:
Fig. 11.1 The origin of life and the theory of life escorted by the deductive method – toward a multidisciplinary unifying synthesis. (a) Darwinian evolution and the origin of life conceptionalized by following the Popperian deductive cycle (Waechtershaeuser 1997). It assumes that science moves from the current reality to the past particulars (top to bottom) and back to the general (same track bottom to top) – a circling, reductionistic, holistic process without end. The path backward in time is chosen by cladistic means following the Darwinian tree of life. As described in the text, first, Belozersky, Crick, Orgel, Woese, Britten & Davidson and Gilbert concluded that RNA was a primordial molecule of an RNA world. LUCAS was the Last Universal Common Ancestral State of all organisms but not a real individual entity as horizontal material, i.e., gene exchange, was common. LUCAS defines the ancient key molecules and metabolic processes present ubiquitously in contemporary life. Following these key processes from root level back-up the tree promises insight into the mechanisms of evolution and the historic and coincidental realities. Wedges (b, c, d) show non-Life Science approaches toward a theory of the origin of life. They can be seen as Popperian deductive mini-cycles that have the potential to fuse with any other deductive cycle. Stanley Miller’s discharge experiments (c) represent the initial root of this bottom-up approach. Here, scientists look at chemical reactions that formed primeval, biologically relevant molecules. The goal is to analyze the variables leading to the initial Darwinian ancestor (IDA). The relevance of such reactions for the origin of life on the protoearth
is then tested experimentally in the laboratory. Geologic and interstellar findings contribute further data of relevance. Between panel (a) on the one hand, and wedges (b, c, d) on the other hand resides the “golden spike”: The “golden spike” is a paraphrase used by Wills and Bada to describe the bottom-up versus the top-down approach (for explanations see footnote 3). The open pentagon at the center represents the hub of interest for all parties. Benner recently noted that any definition of life must incorporate a “theory of life” (Benner et al. 2011). Vice versa, any theory of life must address the origin of life. A working-definition (Lankenau 2006), influenced by all wedges shown, that is compatible with Benner’s requirements is taken as a basis. This biologist’s, anthropic definition (for those who prefer a different) should at least help
initially to focus efforts at understanding: To comprehend the beginnings of life requires that we explain the origin of replication as well as of metabolism synergistically (Maynard Smith and Szathmary 1997). The genetic aspect of the modern definition of life was first proposed by Muller in 1966: “It is to define as alive any entities that have the properties of multiplication, variation and heredity” (Muller 1966). While metabolism supplies the monomers from which the replicators (i.e. genes) are made, replicators alter the kind of chemical reactions occurring in metabolism. Only then can natural selection, acting on replicators, power the evolution of metabolism. The central idea incorporates the need of “instructive genetic information” that can replicate complements. Panel A further depicts the complex and simple three domains of life as discovered by studies on 16S rRNA (Woese and Fox 1977; Woese et al. 1990); Darwin’s tree of life is rooted in the Last Universal Common ancestor (LUCA) that initially existed not as an entity but as the Last Universal Common Ancestral State (LUCAS) (Koonin 2009). Figure in part based on (Benner et al. 2011). The reticulated tree is based in part on (Doolittle 1999).
Notice:
In coalescence theory of population genetics the term "Most Recent Common Ancestor" = MRC is often used, e.g. by Richard Dawkins.
Origins of Life, Biodiversity & Popper´s deductive cycle.
From the Book "Origins of Life":
Fig. 11.1 in:
Lankenau, D.-H. 2011. Two RNA Worlds: Toward the Origin of Replication, Genes, Recombination and Repair, p. 225-286. In R. Egel, D.-H. Lankenau, and A. Y. Mulkidjanian (ed.), Origins of Life: The Primal Self-Organization. Springer Verlag, Heidelberg.
Figure legend:
Fig. 11.1 The origin of life and the theory of life escorted by the deductive method – toward a multidisciplinary unifying synthesis. (a) Darwinian evolution and the origin of life conceptionalized by following the Popperian deductive cycle (Waechtershaeuser 1997). It assumes that science moves from the current reality to the past particulars (top to bottom) and back to the general (same track bottom to top) – a circling, reductionistic, holistic process without end. The path backward in time is chosen by cladistic means following the Darwinian tree of life. As described in the text, first, Belozersky, Crick, Orgel, Woese, Britten & Davidson and Gilbert concluded that RNA was a primordial molecule of an RNA world. LUCAS was the Last Universal Common Ancestral State of all organisms but not a real individual entity as horizontal material, i.e., gene exchange, was common. LUCAS defines the ancient key molecules and metabolic processes present ubiquitously in contemporary life. Following these key processes from root level back-up the tree promises insight into the mechanisms of evolution and the historic and coincidental realities. Wedges (b, c, d) show non-Life Science approaches toward a theory of the origin of life. They can be seen as Popperian deductive mini-cycles that have the potential to fuse with any other deductive cycle. Stanley Miller’s discharge experiments (c) represent the initial root of this bottom-up approach. Here, scientists look at chemical reactions that formed primeval, biologically relevant molecules. The goal is to analyze the variables leading to the initial Darwinian ancestor (IDA). The relevance of such reactions for the origin of life on the protoearth
is then tested experimentally in the laboratory. Geologic and interstellar findings contribute further data of relevance. Between panel (a) on the one hand, and wedges (b, c, d) on the other hand resides the “golden spike”: The “golden spike” is a paraphrase used by Wills and Bada to describe the bottom-up versus the top-down approach (for explanations see footnote 3). The open pentagon at the center represents the hub of interest for all parties. Benner recently noted that any definition of life must incorporate a “theory of life” (Benner et al. 2011). Vice versa, any theory of life must address the origin of life. A working-definition (Lankenau 2006), influenced by all wedges shown, that is compatible with Benner’s requirements is taken as a basis. This biologist’s, anthropic definition (for those who prefer a different) should at least help
initially to focus efforts at understanding: To comprehend the beginnings of life requires that we explain the origin of replication as well as of metabolism synergistically (Maynard Smith and Szathmary 1997). The genetic aspect of the modern definition of life was first proposed by Muller in 1966: “It is to define as alive any entities that have the properties of multiplication, variation and heredity” (Muller 1966). While metabolism supplies the monomers from which the replicators (i.e. genes) are made, replicators alter the kind of chemical reactions occurring in metabolism. Only then can natural selection, acting on replicators, power the evolution of metabolism. The central idea incorporates the need of “instructive genetic information” that can replicate complements. Panel A further depicts the complex and simple three domains of life as discovered by studies on 16S rRNA (Woese and Fox 1977; Woese et al. 1990); Darwin’s tree of life is rooted in the Last Universal Common ancestor (LUCA) that initially existed not as an entity but as the Last Universal Common Ancestral State (LUCAS) (Koonin 2009). Figure in part based on (Benner et al. 2011). The reticulated tree is based in part on (Doolittle 1999).
Notice:
In coalescence theory of population genetics the term "Most Recent Common Ancestor" = MRC is often used, e.g. by Richard Dawkins.