Evolutionary history of tuberculosis deciphered

Or more exactly, the evolutionary history of Mycobacterium tuberculosis complex has been deciphered, indicating that there are two clades:

ScienceDaily (Oct. 22, 2008) — The evolutionary timing and spread of the Mycobacterium tuberculosis complex (MTBC), one of the most successful groups of bacterial pathogens, remains largely unknown. Here, using mycobacterial tandem repeat sequences as genetic markers, we show that the MTBC consists of two independent clades, one composed exclusively of M. tuberculosis lineages from humans and the other composed of both animal and human isolates.

The latter also likely derived from a human pathogenic lineage, supporting the hypothesis of an original human host. Using Bayesian statistics and experimental data on the variability of the mycobacterial markers in infected patients, we estimated the age of the MTBC at 40,000 years, coinciding with the expansion of “modern” human populations out of Africa. Moreover, the diversification of the oldest EAI and LAM populations took place during plant and animal domestication. Science Daily

It’s a somewhat interesting story, particularly due to its relevance to understanding tuberculosis as a disease.

One just has to wonder, in addition, how IDists propose to decide that this branch indicates normal processes of evolution (as at least most self-identified “IDists” would), while another branching happens to be due to design, despite the fact that it reveals no substantially different patterns.  Of course I have brought this up several times already, however it’s worth bringing up yet again, because it is important to understanding diseases like malaria (how adaptable are pathogens?), and because this aspect puts IDists squarely in the camp of creationists and their inability to tell “design” apart from “Darwinism.”

To put it more starkly than I have previously–the methods used for determining clades do not differ substantially across the taxa.  Some of the details change, of course, but the principles, the standards, are the same going back to the Cambrian and beforehand.  Furthermore, they do not differ meaningfully for “suddenly evolving” immunity genes like TCR and BCR (at least parts of which exist in the agnathans–hagfish and lampreys, but are much more diversified and important to jawed vertebrates–the gnathostomes–which use them in their adaptive immune systems, unlike agnathans with their adaptive immune systems), or the apparently far more sedately-changing Toll and Toll-like receptor genes.

Surely it is (in any “design” sense) a mystery of how malaria, tuberculosis, and humans, along with their ancestors, can be phylogenetically analyzed in essentially the same manner no matter whether we study their “designed” parts or their “evolved” parts.  Meaning that there is no obvious difference in causation of evolution across the taxonomic groups (and there is no definite way to assign the taxonomic categories, other than species, although the cladistic branches are not at all arbitrary), and no reason at all to think that design makes any difference to understanding the relationships of pathogens and hosts.  This is important to recognize when analyzing disease and our immune system, as well as when we recognize that Plasmodium spp. are vulnerable to certain drugs precisely because of their very different “lawfully accidental” evolutionary history–which means that drugs targeting the Plasmodium apicoplast have a good chance of being non-toxic to humans.

Then again, in a sense it’s somewhat silly to be discussing the IDist inability to distinguish “design” from “normal evolution” when they have no ability even to show that resistance to chloroquine (which Behe goes on about) actually evolved, rather than be the result of a miracle, or a series of miracles.  The fact is that the IDists attempt to empty science of any and all of the meaning that science gains by matching up cause and effect, and by understanding that similar effects have similar causes (unless, of course, another identifiable cause producing similar effects has been found–IDists only claim that it has, by refusing to differentiate the effects of “design” from those of evolution).

So it’s fail all the way, actually.  Of course they can’t say how “designed clades” differ from “evolved clades,” because they can’t ever rule out “design” with their (lack of) standards.

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Explore posts in the same categories: Darwin's Black Box, News, The Edge of Evolution

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