Peer-Reviewed Article on Transposable Elements Cites “Irreducible Complexity” and Other “Teleologic” Factors
A new peer-reviewed article in Wiley’s eLS, “Transposons in Eukaryotes (Part B): Genomic Consequences of Transposition,” reviews the role of transposable elements (TEs). Plant geneticist Wolf-Ekkehard Lönnig argues that “irreducibly complex” structures may defy explanation by TEs or other Darwinian factors:
A general difficulty to be mentioned in this context (but not inherent in the selfish DNA hypothesis) is that mutation and selection may not be the full explanation for the origin of species; that is, the factors of the neo-Darwinian scenario may find their limits, for example, in the generation of ‘irreducibly complex structures’ (Behe, 2006, 2007). This is a term used to describe structures that, according to Behe, cannot be explained by a piecemeal production via intermediate steps. Among the examples discussed by Behe are the origins of (1) the cilium, (2) the bacterial flagellum with filament, hook and motor embedded in the membranes and cell wall and (3) the biochemistry of blood clotting in humans. Moreover, the traps of Utricularia (Lönnig, 2012) and some other carnivorous plant genera as well as several further apparatus in the animal and plant world appear to pose similar problems for the modern synthesis (joints, echo location, deceptive flowers, the reproductive system of the Australian gastric brooding frog Rheobatrachus silus, the mechanical gears of the nymph stage of the leaf hopper Issus coleoptratus etc.). Up to now, none of these systems has been satisfactorily explained by neo-Darwinism. Whether accelerated TE activities with all the above named mutagenic consequences can solve the questions posed remains doubtful in the eyes of the critical observer. Moreover, natural selection itself may not have the stringency usually ascribed to it (for details, see ReMine, 1993; Lönnig, 2001, 2012, 2014).
(Wolf-Ekkehard Lönnig, “Transposons in Eukaryotes (Part B): Genomic Consequences of Transposition,” In: eLS. John Wiley & Sons, Ltd: Chichester. DOI: 10.1002/9780470015902.a0026265 (August 2015).)
While unguided mutational processes involving TEs seem incapable of producing irreducibly complex structures, the article notes that some believe there may be “teleologic benefits” from TE activities:
Concerning the totally unexpected and extraordinarily high level of current DNA transposition activities in bats in clear contrast to near extinction or absence of such elements in all other mammals, Huang et al. (2012) give sympathetic consideration to ‘teleologic benefits’ (among others) promoting active DNA transposons in the order Chiroptera (perhaps via HT; Tang et al., 2015). A ‘pacemaker proponent’ sensu lato may perhaps ask whether teleologic benefits could also be involved in an independent origin of the Transip TEs and the immune system of jawed vertebrates (not to mention teleology in the sense of Behe, 2006, 2007).
The article cites ID scientists including Jonathan Wells and Richard Sternberg while noting that they and other researchers think that non-coding DNA is largely functional:
In the wake of the ENCODE (encyclopedia of DNA elements) project, several authors are even favouring positions that almost approach the assumption of 100% functional DNA in all genomes, that is, there is no junk DNA in the genomes of plants and animals at all (Shapiro and von Sternberg, 2005;Wells, 2011).
The article concludes by observing that “several lines of evidence” including “irreducibly complex systems” challenge current evolutionary models and should spur us to follow the evidence unswervingly:
[S]everal lines of evidence concerning the origin of life forms, possibly from irreducibly complex systems such as the bacterial flagellum to Darwin’s ‘abominable mystery’ of the origin of angiosperms as well as the Cambrian explosion (for the latter cf. Erwin and Valentine, 2013) may surpass our present knowledge of the causes and factors involved in variation so far known (including TEs) — this, as well as the strongly divergent opinions on TEs and evolution — should be a powerful incentive for further efficient empirical and theoretical research wherever it may lead.
“Wherever it may lead…” That sounds like good advice.
Image: Utricularia pubescens, by Petr Dlouh (Own work) [CC BY-SA 3.0 or GFDL], via Wikimedia Commons.