Summary: Hughes et al. (2010)

It is thought that the human Y chromosome evolved a sex-determining function millions of years ago by gene loss. Given this, theories of decelerating decay predicts that chimpanzee and human male-specific regions on the Y-chromosome (MSY) should not show much divergence. Hughes et al. (2010) accurately and completely sequenced the MSY in the chimpanzee, using large-insert bacterial artificial chromosome clones and iterative mapping and sequencing strategies, in order to compare it to the human MSY. They found differences in sequence structure and gene content, suggesting rapid evolution within the last 6 million years, contrary to the prediction that much divergence should be unlikely. They found that both human and chimp MSY euchromatin is largely comprised of ampliconic and X-degenerate sequence classes but noticed that, while humans have less massive palindromes than chimps, chimps have lost large portions of MSY protein-coding genes and gene families. Hughes et al. (2010) suggest that this divergence in chimp and human MSYs could be driven by four synergistic factors: (1) MSY's role in sperm production; (2) "genetic hitchhiking"; (3) frequent ectopic recombination; and (4) mating behaviour differences. They favour (3): that ectopic recombination between MSY amplicons has sped up MSY structural remodelling in both species. This study is the first to fully compared the Y chromosomes from two closely related species. The importance is two-fold: (1) it provides empirical insight into the evolution of the Y-chromosome; and (2) it provides a test of decelerating decay theories.

Summary: Koboroff et al. (2008)

The two hemispheres of the brain are able to conduct different functions, an ability known as brain lateralization. In birds, brain lateralization has been inferred when a preference to observe a stimulus with one eye ("lateral monocular visual field" is observed. Koboroff et al. (2008) considered that Australian magpies (Gymnorhina tibicen) would show eye preferences when performing anti-predator response. Constant assessment is needed during mobbing behaviour, to make decisions regarding approach, mob or withdraw. They speculated that the left hemisphere would control approach, while the right hemisphere would control withdrawal. However, since mobbing is considered a strong agonistic response, this could be controlled by the right hemisphere (controls intense emotion). Monocular fixations prior to or during performance of mobbing activity in response to perceived predation threat were video recorded. Koboroff et al. (2008) found that, prior to withdrawal, magpies favoured the left eye (85%), while prior to approach, magpies favoured the right eye (72%). Hence, approach in magpies is controlled by the left hemisphere, while withdrawal is favoured by the right hemisphere. They speculate that the left hemisphere is used to process visual inputs prior to approach and the right hemisphere prior to withdrawal. Their results are consistent with hemispheric specialisation in other species, including humans. The relationship between predator-prey interactions and the right hemisphere suggest that the right hemisphere may have, over evolutionary time, organised various anti-predator strategies.

Summary: Sigmund et al. (2010)

Players incur costs when imposing fines on exploiters in 'public goods games'. Even the threat of punishment can increase average pro-social contribution and promote collaborative efforts, yet emergence and stability of costly punishment are problematic. Sigmund et al. (2010) designed a model to compare peer-punishment with pool-punishment, which facilitates the sanctioning of second-order free-riders (those who do not punish exploiters), to determine the most beneficial reward system. The systems are expensive ways to encourage free-riders to cooperate. Spread of second-order free-riders can cause cooperation collapse. Without second-order punishment, the peer-punishment is optimal, but in the presence of second-order punishment, pool-punishers do better. Efficiency is traded for stability. Emergence and stability of costly punishing systems, which regulate common group resources and enforce collaborative efforts, do not require group selection or higher authority prescription. While Sigmund et al. (2010)'s model is minimialistic, it is sound in principle.