Abiogenesis

Thanks Con, Age of the Earth: I only briefly mentioned Uranium-Lead dating, but dozens of other techniques exist which converge on the same age.[1] Uranium-lead dating has the distinct advantage in that both of Uranium’s extant isotopes (U235 & U238) decay at different rates and to two independent isotopes of lead (Pb206, Pb207 respectively) which allows for a very straightforward internal cross-check of the dates obtained. The assumptions work for any original starting concentration of Uranium, and the only thing that needs be controlled for is the original starting concentration of lead.[2] Zircon crystals have a distinct advantage in this aspect as lead is not incorporated in the crystal structure during the zircon crystallization process, whereas uranium freely substitutes with zirconium in the lattice. Given that all the other methods also converge on essentially the same date found by U-Pb, it grants great confidence the results are genuine, and indeed numerous ad-hoc or special pleading layers are required to ‘explain away’ the results found, which quickly falls to Occum’s Razor with the simplest explanation being the Earth really is 4.5 billion years old. The paper Pro cites for his anti-arguments and the helium diffusion data are not peer-reviewed, and are not replicated whatsoever in the literature. A search on WebOfScience [3] (a top library of scientific journals) for the terms “zircon helium diffusion” yielded 112 results, over half of these detailed the use of helium diffusion as a dating method and not one reproduces the findings that Pro asserts (they all cite tens/hundreds of millions of years). Therefore this research cannot be taken seriously unless independently ratified. Order of Fossils: I will not say too much on this other than it literally flies in the face of everything known in geology. Not a single extant mammal found in pre-cretacious layers, and not a single tree found below the cambrian layers (which would be expected if they had existed when the flood occurred), amongst a plethora of other issues. I don’t see this as a sustainable objection given the lack of evidence. Solar System Accretion: Pro drops my points for visual confirmation of the formation of solar systems from gaseous clouds. I also have a number of issues with Con’s arguments against the accretion disk model. 1. Pro doesn’t substantiate why the magnetic field argument makes the accretion model unlikely 2. The lambda-CDM model is irrelivent to the accretion model 3. None of the papers cited has been peer-reviewed, nor reproduced, and therefore are poor quality evidence It is quite simple what the accretion model entails. It entails high abundance of H2 gas distributed throughout the accretion disk, which would react with any O2 to form H2O, which is a highly energetic reaction. The fact we never observe O­2 in any non-earth object in spectroscopy pretty much confirms this. There are many methods to determine the oxygen composition of the early Earth athmosphere, such as ‘red beds’.[4] Fe(III) is the oxidation state of iron formed in the presence of O2, and is insoluble in water, whereas Fe(II) is the oxidation state of iron in a reducing atmosphere, and is much more soluble in water. As the atmospheric oxygen levels increased, the amount of red band laid down will increase, as the Fe(II) acts effectively as an ‘oxygen sink’, and vice versa. Banded red beds stopped forming after 2.1 billion years, which clearly indicates the atmosphere was now rich in oxygen and was oxygen poor in the past. RNA Synthesis: Pro drops my points regarding RNA synthesis and also clay-catalysed replication. Please note I provided just one of several potential pathways for synthesis of RNA. Ideal locations for the generation of these compounds include hydrothermal vents, heated ponds, or volcanic regions. Encapsulation: Encapsulation as I argued, solves multiple potential problems very quickly: 1. Absorbs UV radiation 2. It ‘traps’ within it large molecules 3. It filters out large impurities and is permeable to small monomeric reactive molecules 4. It protects the RNA chain from degradation from other environmental factors Moreover, it’s not a particularly unlikely event to occur either, since the conditions to produce RNA are similar to the ones that naturally produce lipids (hydrothermal conditions). The lipid membranes need not be perfect or pure either, as it’s these imperfect membranes that allows small molecules to easily diffuse into the formed vesicles. I have already shown a number of abiogenic pathways to lipid formation although there are others, moreover it is known that these lipids naturally form micelles and vesicles under the conditions I have described. [5] Pro argues that they run into issues with divalent chelating metal ions such as Ca2+ & Mg2+, and this is true. However this is not a black and white situation, for these salts are in equilibrium and not ‘locked away’ as Pro asserts. Moreover different lipids have different salt association properties, with simpler lipids associating more weakly with these ions (and therefore less subject to precipitation), which conveniently are the lipids most accessible abiotically.[6] Chen et al.[7] has shown that fatty acids with glycerol monoesters (a precursor to fatty acids) stabilize the vesicles to Mg2+ and are capable of ribozyme Mg2+ activated activity. Other studies have also demonstrated the much improved stability of mixed-membranes.[8] The vesicles that formed generally are stable at temperatures exceeding 100oC those akin to the conditions found at hydrothermal vents, demonstrating great robustness. Ultraviolet Radiation: Now, regarding Pro’s assertions regarding UV radiation. First of all, his original reference did not control for oxygen-free conditions, which are well-known to initiate some of the radical degradation pathways involved. Secondly, there are numerous environments which are indeed dark, such as underwater hydrothermal vents, for which many of the building blocks of life I have already mentioned are known to spew from, as well as providing the heat required for these processes to occur. Also, as already mentioned encapsulation resolves many of these potential issues. Replication Issues:It is true that having ribozymes free to duplicate any strand of RNA would be disasterous, which is yet another issue encapsulation conveniently resolves. When a polynucleotide is encapsulated, it has no other macromolecule to replicate. It can replicate itself, however, once isolated. Isolated from external macromolecules, self-replication can repeat, with only small molecules, such as nucleotides, able to enter the protocell. Conclusion:I have highlighted several important factors which make abiogenesis likely: 1. The conditions of the early Earth allow for the complex chemistry required for RNA World abiogenesis and also the long timescales that favour the chances of an improbable event to eventually occur 2. There are numerous pathways for producing the required compounds 3. The steps required up to active encapsulated ribozyme activity has been demonstrated experimentally 4. Many of the problems in RNA world hypothesis are dynamically and conceniently solved with general considerations (hydrothermal vent locations, encapsulation) I am most grateful to Con for taking this debate, I wish him best of luck in his future debates, over to Con for his closing! Vote Pro! References:[1] http://www.talkorigins.org...[2] http://www.tulane.edu...[3] http://apps.webofknowledge.com...[4] http://www.globalchange.umich.edu....[5] http://pubs.acs.org...[6] http://www.ncbi.nlm.nih.gov...[7] http://www.ncbi.nlm.nih.gov...[8] http://online.liebertpub.com...[9] http://molbio.mgh.harvard.edu...;