Ng interestsThe authors declare that they have no competing interests.Authors
Ng interestsThe authors declare that they have no competing interests.Authors’ contributionsEVK conceived of the article and wrote the original draft; YIW modified the manuscript and designed and prepared the figures; both authors read, edited and approved the final text.Page 10 of(page number not for citation purposes)Biology Direct 2009, 4: nucleic acids (e.g., from viruses and plasmids) and using it antisense to the genetic material that evolved in Archaea and Bacteria long ago is very close to the definition of Lamarckism. This mechanism is well described in the article. Although there are a number of original papers and reviews on the subject, no one seems to have recognized the significance of the findings with respect to Lamarckism (but see ref. 24 and Acknowledgements). Concerning definitions regarding “adaptation to the original causative factor” or the “adaptive reaction”, at least initially, this is not always the case: Strictly speaking, the CRISPR system is an exaptation. For example, the viral sequences did not evolve for the function in the host; instead the host is co-opting them subsequent to integration for RNA-based antivirus immunity. Perhaps one way out would be the use of the term “aptation” which comprises exaptation and adaptation as suggested by Gould and Vrba [103]. Authors’ response: We think this is a very subtle although, perhaps, valid semantic point. Again, the interested reader will be alerted by the comment. Horizontal gene transfer (HGT), which was rampant in the RNA world [99], I would not hang up too high with respect to Lamarckism. The CRISPR system is a much more impressive example. With respect to HGT, once more I only see a continuum with HGT on one end and sex among members of the same species on the other. HGT is just limit-, border-, or barrierless sex acquiring different genes instead of different alleles [99]. Obviously, I do not quite agree with the view that the “Lamarckian modality is associated primarily, if not exclusively, with the organismal level of complexity, and does not apply to the most fundamental level of evolution which indeed involves genes, independently evolving portions of genes (e.g. those encoding distinct protein domains) and mobile PubMed ID: elements [98]” because of the inseparability of genotype and phenotype in the RNA world [99]. However, I agree with the authors to consider Lamarckism as largely an “emergent phenomenon” (but see the CRISPR system) in our lineage (see memes and other evolutionary transitions discussed above). Stress-induced mutations, whether point mutations including small indels including SOS repair or large indels in the form of mobile genetic elements constitute a crude machinery, at best, but hardly directed. Despite a preference for TTAAAA during RNA 1,1-Dimethylbiguanide hydrochlorideMedChemExpress Metformin (hydrochloride) mediated retroposition in placental mammals [104], insertions can happen at almost any locus and hardly can be considered specific. At a later point, the authors put this in the right perspective. I hope misguided individuals do not stop reading beforethey reach these important paragraphs. Giving an outlook on the future of our species, we might expect a sharp increase in mutations and retroposition, due to the selfinflicted stress by feedback from our environment. Once more, one can only agree with Stephen Jay Gould: “. our deepest puzzles and most fascinating inquiries often fall into a no-man’s land not clearly commanded by either party” [7].Reviewer 2: V.