Promotion of Cooperation by Selective Group Extinction

Multilevel selection is an important organizing principle that crucially underlies evolutionary processes from the emergence of cells to eusociality and the economics of nations. Previous studies on multilevel selection assumed that the effective higher-level selection emerges from lower-level reproduction. This leads to selection among groups, although only individuals reproduce. We introduce selective group extinction, where groups die with a probability inversely proportional to their group fitness. When accounting for this the critical benefit-to-cost ratio is substantially lowered. Because in game theory and evolutionary dynamics the degree of cooperation crucially depends on this ratio above which cooperation emerges previous studies may have substantially underestimated the establishment and maintenance of cooperation.Comment: Accepted for publication in New Journal of Physic

Possible Origin of Stagnation and Variability of Earth's Biodiversity

The magnitude and variability of Earth's biodiversity have puzzled scientists ever since paleontologic fossil databases became available. We identify and study a model of interdependent species where both endogenous and exogenous impacts determine the nonstationary extinction dynamics. The framework provides an explanation for the qualitative difference of marine and continental biodiversity growth. In particular, the stagnation of marine biodiversity may result from a global transition from an imbalanced to a balanced state of the species dependency network. The predictions of our framework are in agreement with paleontologic databases.Comment: 5 pages, 6 pages supplemen

Crackling Noise in Fractional Percolation -- Randomly distributed discontinuous jumps in explosive percolation

Crackling noise is a common feature in many systems that are pushed slowly, the most familiar instance of which is the sound made by a sheet of paper when crumpled. In percolation and regular aggregation clusters of any size merge until a giant component dominates the entire system. Here we establish `fractional percolation' where the coalescence of clusters that substantially differ in size are systematically suppressed. We identify and study percolation models that exhibit multiple jumps in the order parameter where the position and magnitude of the jumps are randomly distributed - characteristic of crackling noise. This enables us to express crackling noise as a result of the simple concept of fractional percolation. In particular, the framework allows us to link percolation with phenomena exhibiting non-self-averaging and power law fluctuations such as Barkhausen noise in ferromagnets.Comment: non-final version, for final see Nature Communications homepag

Oregon’s new voter registration law will make votingeasier—but higher turnout will depend on parties andcandidates

Last month, Oregon introduced an innovative new voter registration law, which will see people automatically registered to vote when they register with the state’s department of motor vehicles. Jan Leighley and Jonathan Nagler write that Oregon’s new law should be seen against a backdrop of changing voting laws which include measures which make voting easier, such as early voting, absentee voting, and Election Day registration, and voter identification laws which make voting more difficult. They argue that while Oregon’s new law- and others like it- should help encourage people to vote candidates must also give them good reasons to do s

Controlling percolation with limited resources

Connectivity - or the lack thereof - is crucial for the function of many man-made systems, from financial and economic networks over epidemic spreading in social networks to technical infrastructure. Often, connections are deliberately established or removed to induce, maintain, or destroy global connectivity. Thus, there has been a great interest in understanding how to control percolation, the transition to large-scale connectivity. Previous work, however, studied control strategies assuming unlimited resources. Here, we depart from this unrealistic assumption and consider the effect of limited resources on the effectiveness of control. We show that, even for scarce resources, percolation can be controlled with an efficient intervention strategy. We derive this strategy and study its implications, revealing a discontinuous transition as an unintended side-effect of optimal control.Comment: 5 pages, 4 figures, additional supplemental material (19 pages

Spatial representations of numbers and letters in children

Different lines of evidence suggest that children's mental representations of numbers are spatially organized in form of a mental number line. It is, however, still unclear whether a spatial organization is specific for the numerical domain or also applies to other ordinal sequences in children. In the present study, children (n = 129) aged 8–9 years were asked to indicate the midpoint of lines flanked by task-irrelevant digits or letters. We found that the localization of the midpoint was systematically biased toward the larger digit. A similar, but less pronounced, effect was detected for letters with spatial biases toward the letter succeeding in the alphabet. Instead of assuming domain-specific forms of spatial representations, we suggest that ordinal information expressing relations between different items of a sequence might be spatially coded in children, whereby numbers seem to convey this kind of information in the most salient way

Unfair and Anomalous Evolutionary Dynamics from Fluctuating Payoffs

Evolution occurs in populations of reproducing individuals. Reproduction depends on the payoff a strategy receives. The payoff depends on the environment that may change over time, on intrinsic uncertainties, and on other sources of randomness. These temporal variations in the payoffs can affect which traits evolve. Understanding evolutionary game dynamics that are affected by varying payoffs remains difficult. Here we study the impact of arbitrary amplitudes and covariances of temporally varying payoffs on the dynamics. The evolutionary dynamics may be "unfair", meaning that, on average, two coexisting strategies may persistently receive different payoffs. This mechanism can induce an anomalous coexistence of cooperators and defectors in the Prisoner's Dilemma, and an unexpected selection reversal in the Hawk-Dove game.Comment: 6 pages, 8 pages supplemen

The Potential of Ridesharing Adoption and its Effects on CO2 Emissions and Customer Experience

Taxi services are an integral part of urban transport and are a major contributor to air pollution and traffic congestion, which adversely affect human life and health. Sharing taxi rides is one way to reduce the unfavorable effects of cab services on cities. However, this comes at the expense of passenger discomfort, quantified in terms of longer travel times. Taxi ridesharing is a sophisticated mode of urban transport that combines individual trip requests with similar spatiotemporal characteristics into a shared ride. We propose a one-to-one sharing strategy that pairs trips with similar starting and ending points. We examine the method using an open dataset with trip information on over 165 million taxi rides. We show that the cumulative journey time can be reduced by 48 percent while maintaining a relatively low level of passenger inconvenience, with a total average delay compared to an individual mobility case of 6 minutes and 42 seconds. This advantage is accompanied by decreases in emissions of 20.129 tons on an ordinary day and a potential fare reduction of 49 percent, which could point to a widespread passenger acceptance of shared taxi services. Overall, a matching rate of 13 percent is reached while a 27 percent matching rate is attained for high-demand areas. Compared to many-to-many sharing dynamic routing methodologies, our scheme is easier to implement and operate, making fewer assumptions about data availability and customer acceptance