The Efficacy of Group Selection is Increased by Coexistence Dynamics within Groups

Selection on the level of loosely associated groups has been suggested as a route towards the evolution of cooperation between individuals and the subsequent formation of higher-level biological entities. Such group selection explanations remain problematic, however, due to the narrow range of parameters under which they can overturn within-group selection that favours selfish behaviour. In principle, individual selection could act on such parameters so as to strengthen the force of between-group selection and hence increase cooperation and individual fitness, as illustrated in our previous work. However, such a process cannot operate in parameter regions where group selection effects are totally absent, since there would be no selective gradient to follow. One key parameter, which when increased often rapidly causes group selection effects to tend to zero, is initial group size, for when groups are formed randomly then even moderately sized groups lack significant variance in their composition. However, the consequent restriction of any group selection effect to small sized groups is derived from models that assume selfish types will competitively exclude their more cooperative counterparts at within-group equilibrium. In such cases, diversity in the migrant pool can tend to zero and accordingly variance in group composition cannot be generated. In contrast, we show that if within-group dynamics lead to a stable coexistence of selfish and cooperative types, then the range of group sizes showing some effect of group selection is much larger

Propagating Waves in Human Motor Cortex

Previous studies in non-human primates (NHPs) have shown that beta oscillations (15–30 Hz) of local field potentials (LFPs) in the arm/hand areas of primary motor cortex (MI) propagate as traveling waves across the cortex. These waves exhibited two stereotypical features across animals and tasks: (1) The waves propagated in two dominant modal directions roughly 180° apart, and (2) their propagation speed ranged from 10 to 35 cm/s. It is, however, unknown if such cortical waves occur in the human motor cortex. This study shows that the two properties of propagating beta waves are present in MI of a tetraplegic human patient while he was instructed to perform an instruction delay center-out task using a cursor controlled by the chin. Moreover, we show that beta waves are sustained and have similar properties whether the subject was engaged in the task or at rest. The directions of the successive sustained waves both in the human subject and a NHP subject tended to switch from one dominant mode to the other, and at least in the NHP subject the estimated distance traveled between successive waves traveling into and out of the central sulcus is consistent with the hypothesis of wave reflection between the border of motor and somatosensory cortices. Further, we show that the occurrence of the beta waves is not uniquely tied to periods of increased power in the beta frequency band. These results demonstrate that traveling beta waves in MI are a general phenomenon occurring in human as well as NHPs. Consistent with the NHP data, the dominant directions of the beta LFP waves in human aligned to the proximal to distal gradient of joint representations in MI somatotopy. This consistent finding of wave propagation may imply the existence of a hardwired organization of motor cortex that mediates this spatiotemporal pattern

Post-Meiotic Intra-Testicular Sperm Senescence in a Wild Vertebrate

There is growing interest in sperm senescence, both in its underlying mechanisms and evolutionary consequences, because it can impact the evolution of numerous life history traits. Previous studies have documented various types of sperm senescence, but evidence of post-meiotic intra-testicular sperm senescence in wild animals is lacking. To assess such senescence, we studied within-season changes in sperm motility in the common toad (Bufo bufo), where males produce all sperm prior to the breeding season. We found that males exposed to experimentally induced re-hibernation at the start of the breeding season, that is to experimentally lowered metabolic rates, stored sperm of significantly higher motility than males that were kept under seminatural conditions without females throughout the breeding season. This finding indicates that re-hibernation slows normal rates of sperm ageing and constitutes the first evidence to our knowledge of post-meiotic intra-testicular sperm senescence in a wild vertebrate. We also found that in males kept in seminatural conditions, sperm motility was positively related to the number of matings a male achieved. Thus, our results suggest that post-meiotic intratesticular sperm senescence does not have a genetically fixed rate and may be modulated by temperature and possibly by mating opportunities

Improving therapeutic potential of GDNF family ligands

The last decade has been a frustrating time for investigators who had envisioned major advances in the treatment of Parkinson's disease using neurotrophic factors. The first trials of glial cell line-derived neurotrophic factor for treating Parkinson's disease were very promising. Later blinded control trials were disappointing, not reaching the predetermined outcomes for improvement in motor function. Consideration of the problems in the studies as well as the biology of the neurotrophins used can potentially lead to more effective therapies. Parkinson's disease presents a multitude of opportunities for the cell biologist wanting to understand its pathology and to find possible new avenues for treatment.Peer reviewe

Adaptation without natural selection

Document is itself an extended abstract

Metamorphosis as a narrative strategy in selected South African animated films

Abstract This study examines the notion as well as the use of metamorphosis in the animated films of selected South African artists. The analysis demonstrates how metamorphosis, as a narrative strategy, is wholly appropriate to South African animation artists whose works engage with issues which tend to surface in a country in constant flux and in which the word ‘transformation’ is part of its everyday vocabulary and collective consciousness. I bring together ideas around metamorphosis from various animation writers and link these to an eclectic selection of writers in other fields. I examine W.J.T. Mitchell’s writing on the multistable image as well as the work of neuroscientist, V.S. Ramachandran in order to suggest a possible explanation for the hold that metamorphosis has over its audience. I also included an alternative history of animation via the transformative, Vaudeville performances of chapeaugraphy, shadowgraphy and Quick-Change. In addition I differentiate between the digital morph as exemplified in the music video to Michael Jackson’s Black or White (1991) and the type of hand-drawn metamorphosis in the work of William Kentridge. The issue at stake here is the ability of the morph to transgress arbitrary boundaries of categorisation versus its tendency to obliterate otherness and inculcate sameness. For my case studies I examine William Kentridge’s use of metamorphosis in his Drawings for Projection and how metamorphosis is apparent not only in the transformation of one object into another, but at the level of the medium itself. Here I look at how his work is infused with metaphor through the palimpsetic traces left behind by the incomplete erasures of his technique. As a loose framework around the discussion of metaphor I look at the theories of Paul Ricoeur and the more poetic writing of Cynthia Ozick. In the on-going time lapse collaboration project Minutes by Mocke Lodewyk Jansen van Veuren and Theresa Collins I examine how both the city and our experience of time and space is transformed through time lapse animation and how this transformation enables an analysis of spatial practice that can be utilized in future urban renewal programmes. In my own work, I am interested in exploring the theme of origins. I look at genetics and cosmology as well as Deleuze’s theory of individuation and how they all seem to incorporate a kind of ‘metastable state’ of infinite potential that is similar to Eisenstein’s “plasmaticness”. As a visual idiom I use static ‘snow’ or ‘noise’ in animation, video work and drawings; conceptually harnessing the idea that static contains residual radiation left over from the birth of the universe. Static noise is the medium through which I create portraits of my father and encounter my own ‘genetic‘ self-portrait. I also analyse some of the work on physical actions by theatre theorist and director Jerzy Grotowski. From Grotowski, I have begun to understand certain performative aspects around gesture and the simultaneous portrait/self-portrait see-saw of my work