JLT
Posts: 740
Joined: Jan. 2008
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Joseph demonstrates why IDists deserve to be ridiculed:
| Quote | | As for Allen’s continuing to say tat euks evolved from proks via SET, there is also scientific data which demonstrates that proks “devolved” from euks- euks came first. |
As support for this he links to an MSNBC article that is based on an article by Kurland, Collins, and Penny in Science 2006 (Genomics and the Irreducible Nature of Eukaryote Cells). The MSNBC article wouldn't be too bad if they hadn't included this bit:
| Quote | | It’s just a joke, but the idea that life starts simple and gets more complex over time persists even in scientific circles. Yet one of the biggest events in evolutionary history — the origin of the cells that make up every tissue in our bodies — may be a case of life getting less complicated, according to recent research. |
That's complete and utter bullshit.
To explain why, a little science. The following is from an article by Yutin et al. (2008). The Deep Archaeal Roots of Eukaryotes (free fulltext). Molecular Biology and Evolution.*
| Quote | Two key observations that must be taken into account by any concept of eukaryotic origin are currently not contested seriously.
1. All extant eukaryotes evolved from a common ancestor that already possessed an a-proteobacterial endosymbiont that gave rise to the mitochondria and their degraded relatives, hydrogenosomes and mitosomes (van der Giezen and Tovar 2005; Embley 2006).
2. Eukaryotes possess 2 distinct sets of genes, one of which shows apparent phylogenetic affinity with homologs from archaea and the other one is more closely related to bacterial homologs (not all eukaryotic genes belong to these 2 sets, of course; many are of uncertain origin, and many more appear to be unique to eukaryotes). There is a clear functional divide between the ‘‘archaeal’’ and ‘‘bacterial’’ genes of eukaryotes, with the former encoding, largely, proteins involved in information processing (translation, transcription, replication, and repair) and the latter encoding proteins with ‘‘operational’’ functions (metabolic enzymes, components of membranes, and other cellular structures, etc.) (Esser et al. 2004; Rivera and Lake 2004). In some of the informational and operational systems, the archaeal and bacterial affinities, respectively, of eukaryotic genes are manifest qualitatively: Thus, the key proteins involved in DNA replication in archaea and eukaryotes are not homologous to the functionally analogous proteins of bacteria (Leipe et al. 1999), and conversely, some of the principal enzymes of membrane biogenesis are homologous in eukaryotes and bacteria but not in archaea (Pereto et al. 2004).
Apparently, the most parsimonious scenario of eukaryogenesis combining these 2 key facts is that the first eukaryote was an archaeal–bacterial chimera that emerged as a result of an invasion of an archaeon by an a-proteobacterium, the well-established ancestor of the mitochondria (Martin and Muller 1998; Rivera and Lake 2004; Martin and Koonin 2006). However, this is by no means the only scenario of eukaryotic origins that is currently actively considered (Embley and Martin 2006; Poole and Penny 2007b). The main competitor is, probably, the archezoan hypothesis under which the host of the a-proteobacterial endosymbiont was not an archaeon but a primitive, obviously, amitochondrial, proto-eukaryote that already possessed the hallmarks of the eukaryotic cell, such as the endomembrane system, the nucleus, and the cytoskeleton (Kurland et al. 2006; Poole and Penny 2007a). The symbiotic scenarios substantially differ from the archezoan hypothesis with respect to the level of complexity that is attributed to the host of the mitochondrial endosymbiont. Under the symbiotic hypotheses, the host was a ‘‘garden variety’’ archaeon, with the dramatic complexification of the cellular organization being triggered by the symbiosis. In contrast, the archezoan hypothesis posits that, at least, some substantial aspects of the characteristic eukaryotic complexity (e.g., the endomembrane system) evolved prior to and independent of the symbiosis and were already in place in the organism that hosted the mitochondrion. Under the archezoan scenario, the presence of archaea-like genes in the ancestral eukaryotic gene set is, then, explained either by postulating that the proto-eukaryotic lineage was a sister group of archaea and/or by horizontal transfer of archaeal genes. The archezoan hypothesis was seriously undermined by the realization that all unicellular eukaryotes previously thought to be primitively amitochondrial actually possess degraded organelles of a-proteobacterial descent. Nevertheless, the archezoan scenario stays alive, with the proviso that the ancestral archezoan lineage had gone extinct (Poole and Penny 2007a). |
Much shorter: There're two main scenarios which are debated, the symbiogenetic scenario and the archezoan scenario.
In the symbiogenetic scenario the host for the a-proteobacterial ancestor of mitochondria didn't have a nucleus, an endomembrane system or a cytoskeleton and the symbiosis triggered "eukaryogenesis".
In the archaeozoan scenario, the host already had some features that are characteristic for eukaryotes and correspondingly these features evolved independently of the endosymbiosis.
But even in the latter scenario by no means was the "proto-eukaryote" more complex than extant eukaryotic cells**. What Penny et al proposed is that extant bacteria could be simplified "proto-eukaryotes", but apparently Penny revised this view in a later article (2007) because of new findings.
The other problem with the MSNBC article is that it is completely one-sided. From a quick look at the literature it's clear that it's a highly controversial topic. Scientific controversies are almost never settled with a single article and as the Koonin article I linked to shows this specific controversy definitely isn't settled.
The MSNBC article doesn't mention that at all (in their defense I've to say that Penny argues as if the controversy were settled with his Science article).
If Joseph was really interested in the scientifically best explanation rather than in the explanation that fits his religious convictions best he would know all this as well.
But Joseph, ideology driven as he is, takes this one-sided non-scientific article which happens to fit his preconceived opinion as absolute truth and never ever asks himself whether there may be more to that story.
They never do.
* Disclaimer: Koonin is one of the authors and he's in favour of the symbiogenetic scenario.
** If one thinks that more organelles = more complex. Penny et al. fully accept the endosymbiotic origin of e. g. mitochondria.
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"Random mutations, if they are truly random, will affect, and potentially damage, any aspect of the organism, [...]
Thus, a realistic [computer] simulation [of evolution] would allow the program, OS, and hardware to be affected in a random fashion." GilDodgen, Frilly shirt owner
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