From: bivalve (bivalve@mail.davidson.alumlink.com)
Date: Fri Oct 31 2003 - 17:38:06 EST
>"D. F. Siemens, Jr." wrote:
>>bacterial and viral genes have been incorporated in most genomes by transfer. It has nothing to do with descent. I find it hard to believe that anyone with even the most rudimentary familiarity with the literature would make a statement like Anderson's.<<
Anderson replied
>"As for the comment about these genes not resulting from common descent, I could not agree more. However, there are a number of evolutionary scientists, including one of the leaders of the DOE's genome project, that are saying exactly that --
the presence of these genes in the human genome is evidence of common descent (ex. see Nature. 2001. 411:940; Science. 2001. 292:1903). Perhaps you would want to contact these various evolutionists and explain to them their incredible ignorance.
>"Yes, some evolutionists do insist such HGT between bacteria and humans occurred recently (ex. TIG. 2001. 17:235). But, they have no explanation of how this happened, only speculation. Therefore, would you please provide even one demonstrated means by which bacterial genes can be incorporated into the human gene line. This information is apparently widely and thoroughly known so you should have no problem quickly providing such information.<
Although calling Anderson a braying jackass is neither polite nor very helpful in encouraging him to repent, his statement is indeed deficient in quality and accuracy.
Many genes shared between humans (or other eukaryotes) and prokaryotes appear to reflect ultimate common descent (e.g., nuclear ribosomal genes compared with eubacterial and archaean ribosomal genes). These give broad agreement in evolutionary patterns. Others appear to represent more recent lateral transfer events. These will show obviously aberrant evolutionary patterns, in the case of transfer between bacteria and humans (or moderately recent human ancestors), though within each group they will probably show consistent patterns. E.g., suppose a gene transferred from E. coli to the common ancestor of great apes and humans. Study of this gene would produce a phylogeny that put apes and humans closer to E. coli than to other primates. This would be the true evolutionary tree for that gene, but not for the organisms as a whole. However, within the great ape and human group, the gene would be expected to show the same evolutionary pattern as any other gene without latera!
l transfer.
Anderson misrepresents this by trying to claim that either all genes reflect common descent or all reflect lateral transfer.
As to mechanisms for lateral gene transfer, I am not certain what sort of evidence Anderson wants. Even though he claims not to believe in lateral gene transfer, I doubt that he would be willing to volunteer for an experiment to try to alter his DNA via lateral transfer of bacterial genes. Short of such unethical experiments, it would be difficult to prove conclusively that bacteria to human transfers can take place in a live human being. However, viruses are not constrained by research ethics and transfer their genes into humans and other organisms all the time. This is one easy way for assorted stray DNA, especially viral sequences, to transfer between species. If the virus picks up a little stray DNA, this can be transferred as well. This technique is widely used in genetic manipulation of lab organisms. Although there are a number of protective mechanisms against foreign DNA in the cell, stray DNA can be taken up and incorporated into the genome (especially in bac!
teria, more difficult in eukaryotes, with corresponding high and low rates of lateral transfer). The mitochondria represent another important source of lateral transfer of genes from a eubacterial source into eukaryotic genomes.
The possibility of lateral transfer in bacteria has been known for many decades; in fact, it was one of the early lines of evidence for the importance of DNA in cell function (mouse+harmless bacteria+DNA from dead harmful bacteria=dead mouse+harmful bacteria).
To me, it seems honest to assert that one does not think that the genetic patterns reflect common descent or lateral transfer, while acknowledging that common descent and lateral transfer are consistent with the physical evidence and internally consistent with current evolutionary understanding. It is the inaccurate disparaging of evolution that is the problem.
Dr. David Campbell
Old Seashells
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Box 870345
Tuscaloosa, AL 35487-0345 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
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