Evolution is frequently concentrated in bursts of rapid morphological change and speciation followed by long‐term stasis. We propose that this pattern of punctuated equilibria results from an evolutionary tug‐of‐war between host genomes and transposable elements (TEs) mediated through the epigenome. According to this hypothesis, epigenetic regulatory mechanisms (RNA interference, DNA methylation and histone modifications) maintain stasis by suppressing TE mobilization. However, physiological stress, induced by climate change or invasion of new habitats, disrupts epigenetic regulation and unleashes TEs. With their capacity (...) to drive non‐adaptive host evolution, mobilized TEs can restructure the genome and displace populations from adaptive peaks, thus providing an escape from stasis and generating genetic innovations required for rapid diversification. This “epi‐transposon hypothesis” can not only explain macroevolutionary tempo and mode, but may also resolve other long‐standing controversies, such as Wright's shifting balance theory, Mayr's peripheral isolates model, and McClintock's view of genome restructuring as an adaptive response to challenge. (shrink)

Transposable elements (TEs) are powerful facilitators of genome evolution, and hence of phenotypic diversity as they can cause genetic changes of great magnitude and variety. TEs are ubiquitous and extremely ancient, and although harmful to some individuals, they can be very beneficial to lineages. TEs can build, sculpt, and reformat genomes by both active and passive means. Lineages with active TEs or with abundant homogeneous inactive populations of TEs that can act passively by causing ectopic recombination are potentially fecund, adaptable, (...) and taxonate readily. Conversely, taxa deficient in TEs or possessing heterogeneous populations of inactive TEs may be well adapted in their niche, but tend to prolonged stasis and may risk extinction by lacking the capacity to adapt to change, or diversify. Because of recurring intermittent waves of TE infestation, available data indicate a compatibility with punctuated equilibrium, in keeping with widely accepted interpretations of evidence from the fossil record. We propose a general and holistic synthesis on how the presence of TEs within genomes makes them flexible and dynamic, so that genomes themselves are powerful facilitators of their own evolution. (shrink)

The issue of the biological origin of consciousness is linked to that of its function. One source of evidence in this regard is the contrast between the types of information that are and are not included within its compass. Consciousness presents us with a stable arena for our actions—the world—but excludes awareness of the multiple sensory and sensorimotor transformations through which the image of that world is extracted from the confounding influence of self-produced motion of multiple receptor arrays mounted on (...) multijointed and swivelling body parts. Likewise excluded are the complex orchestrations of thousands of muscle movements routinely involved in the pursuit of our goals. This suggests that consciousness arose as a solution to problems in the logistics of decision making in mobile animals with centralized brains, and has correspondingly ancient roots. (shrink)

Cephalopods are extraordinary molluscs equipped with vertebrate‐like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530 Ma) from a monoplacophoran‐like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid‐Palaeozoic (∼416 Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish (...) and octopods) internalised their shells and, in the late Palaeozoic (∼276 Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour. (shrink)