Where and what is the right shift factor or cerebral dominance gene? A critique of Francks et al. (2007).

Francks et al. (2007, p. 1129) claim to have identified "The first potential genetic influence on human handedness ... and the first putative genetic effect on variability in human brain asymmetry" and a gene "that underlies much of human cognition, behaviour and emotion" (p. 1129). We criticise this claim on the basis that the authors have made unjustified assumptions concerning mode of transmission both of psychosis and relative hand skill, that they have failed to establish a parent of origin effect, and have overlooked previous findings concerning the genetic basis of handedness and asymmetry. We suggest that some of these errors relate to the application of linkage disequilibrium to detect variation that is common in the population and relates to the characteristic that defines the species. While we agree (and indeed first proposed) that the variation underlying psychosis is intrinsically related to the cerebral torque, which we take to be the anatomical basis of language, we are unconvinced by the data for LRRTM1 presented by Francks et al. We consider that a stronger case can be mounted for the Protocadherin11X/Y gene pair located in the hominid specific Xq21.3/Yp11.2 region of homology that was generated by a duplication from the X between 6 and 5 million years ago and that has been subject to a number of chromosomal and sequence changes. This gene pair can account for relationships between relative hand skill and verbal and non-verbal ability that are sex dependent, and morphological changes in the brain in psychosis that reflect interactions between sex and laterality, which are already established in the literature

Where and what is the right shift factor or cerebral dominance gene? A critique of Francks et al. (2007).

Francks et al. (2007, p. 1129) claim to have identified "The first potential genetic influence on human handedness ... and the first putative genetic effect on variability in human brain asymmetry" and a gene "that underlies much of human cognition, behaviour and emotion" (p. 1129). We criticise this claim on the basis that the authors have made unjustified assumptions concerning mode of transmission both of psychosis and relative hand skill, that they have failed to establish a parent of origin effect, and have overlooked previous findings concerning the genetic basis of handedness and asymmetry. We suggest that some of these errors relate to the application of linkage disequilibrium to detect variation that is common in the population and relates to the characteristic that defines the species. While we agree (and indeed first proposed) that the variation underlying psychosis is intrinsically related to the cerebral torque, which we take to be the anatomical basis of language, we are unconvinced by the data for LRRTM1 presented by Francks et al. We consider that a stronger case can be mounted for the Protocadherin11X/Y gene pair located in the hominid specific Xq21.3/Yp11.2 region of homology that was generated by a duplication from the X between 6 and 5 million years ago and that has been subject to a number of chromosomal and sequence changes. This gene pair can account for relationships between relative hand skill and verbal and non-verbal ability that are sex dependent, and morphological changes in the brain in psychosis that reflect interactions between sex and laterality, which are already established in the literature

Southern Ocean primary production - constraints from predator carbon demand and nutrient drawdown

In view of the wide range of estimates for the total primary production for the Southern Ocean south of the Subantarctic Front-current estimates range from 1.2 to 3.5 Gtonne C year(-1) -we have examined two indirect methods for assessing primary production. First, we have estimated the primary production needed to sustain the carbon requirements of the endotherm top predators in the ecosystem. Estimation of the carbon requirements for crabeater seals of about 7 Mtonne C year(-1) is extrapolated to a value for all endotherm predators of 15-30 Mtonne C year(-1). Current data indicate that 70-80% of the diet of this suite of predators is zooplankton (predominantly the euphausiid krill), making for highly efficient transfer from primary production to top predators. Our best estimate of Southern Ocean primary production by this method is of the order of 1.7 Gtonne C year(-1), or an averaged areal primary production of about 30-40 g C m(-2) year(-1). Our second approach is to estimate primary production from the drawdown of inorganic nutrients, based on the Limited suite of studies from which an annual nutrient deficit can be calculated. Again, this indicates annual primary production of the order of 1.5 Gtonne. Although both methods have inherent uncertainties, taken together they provide a relatively robust constraint on annual primary production. For both methods to underestimate primary production by the 1-1.5 Gtonne C implied by the higher current estimates, carbon export from the Southern Ocean pelagic ecosystem would need to be much higher than is normally found in other oceans.</p

Interannual variability of the South Georgia marine ecosystem: biological and physical sources of variation in the abundance of krill

Interannual variability is a characteristic feature of the Southern Ocean ecosystem, yet the relative roles of biological and physical processes in generating these fluctuations are unknown. There is now extensive evidence that there are years when there is a very low abundance of Antarctic krill (Euphausia superba) in the South Georgia area, and that this variation affects much of the ecosystem, with the most obvious impacts on survival and breeding success of some of the major predators on krill. The open nature of the South Georgia ecosystem means this variability has large-scale relevance, but even though there are unique time series of data available, information on some key processes is limited. Fluctuations in year-class success in parts, or all, of the krill population across the Scotia Sea can generate large changes in the available biomass. The ocean transport pathways maintain the large-scale ecosystem structure by moving krill over large distances to areas where they are available to predator colonies. This large-scale physical system shows strong spatial and temporal coherence in the patterns of the interannual and subdecadal variability. This physical variability affects both the population dynamics of krill and the transport pathways, emphasizing that both the causes and the consequences of events at South Georgia are part of much larger-scale processes.</p