(Original post by whyumadtho)
"The theory of UCA allows for the possibility of multiple independent origins of life" (Theobald, 2010). That image doesn't refute this and I believe you are attacking a straw man.
They didn't undermine the UCA as a concept, it just undermines one author's pioneering attempt to reconcile the overwhelming pieces of evidence that support the UCA. Multiple theories that necessitate its presence and/or have demonstrated its likely existence independently can be observed to hold true (Lombard et al
., 2012; Mulkidjanian et al.
, 2012; Fuerst and Sagulenko, 2012; Copley, 2012; Creevey et al.
, 2012; Yu and Xu, 2011; amongst many
others). Opitz (2011) suggests, "[h]orizontal gene transfer complicates the task of tracing descent; however, in a post-RNA world it is evident that the three domains of life share so many properties (homologies) that common ancestry is the only logical conclusion", and continues by saying, "with modern methods it is possible to obtain inferences about [the LUCA's] biologic nature; [(Forterre and Philippe, 1999; Di Giulio, 2011; Glansdorff et al
., 2008; Foreterre, 2005; Becerra et al.
, 2007; Hoenigsberg, 2003 and Doolittle, 2000)] its genetic constitution and content; [(Creevey et al
., 2011; Tuller et al
., 2010; Mushegian, 2008; Mat et al
., 2008; Ouzounis et al
., 2006)] and its protein molecules [(Ranea et al.
, 2006; Sobolevsky and Trifonov, 2006)]."
UCA has virtually reached the status of a biological axiom, but the shape
of descent is what I now realise is disputed (however, this recent article has used multiple methods that produced treelike patterns: Abby et al
Despite everything I've said above, those two questions I presented in the post before last remain extant: "We might entertain different sorts of hierarchical, multidimensionally clustered or reticulated classifications for different sorts of purposes. Alternatively, we could stick with current rRNA-based or total-proteome classifications, with the full admission that at the very best they are only just 'more natural' than other systems, in that more (or more 'fundamental') data may support them. But as with the placement of books on library shelves, there is in principle, no final truth of such matters" (Doolittle, 2009).
My logical argument and Barbujani and Belle's (2006) conclusion remain standing, and, in fact, the Doolittle (2009) article lends strong support to the socially constructed nature of various categorisation systems. As I said, disagreement occurs at every stage but increases as one descends. At the top, there is more agreement over various concepts (insofar as some are widely treated as axiomatic), but there are still alternative theories that are possible depending on the assumptions, methodologies and datasets used.
In addition, how does this lend support to your fundamental point? This is one of the many discrepancies of the domain stage and has no bearing on anything below. You were previously arguing that 'races' existed due to supposedly discrete phylogenetic lineages (wrong), and now you are discrediting the notion of discrete phylogenetic lineages due to lateral transfer.