Human cooperation and altruism towards non-kin is a major evolutionary puzzle, as is 'strong reciprocity' where no present or future rewards accrue to the co-operator/altruist. Here, we test the hypothesis that the development of extra-somatic weapons could have influenced the evolution of human cooperative behaviour, thus providing a new explanation for these two puzzles. Widespread weapons use could have made disputes within hominin groups far more lethal and also equalized power between individuals. In such a cultural niche non-cooperators might well have become involved in such lethal disputes at a higher frequency than cooperators, thereby increasing the relative fitness of genes associated with cooperative behaviour. We employ two versions of the evolutionary Iterated Prisoner's Dilemma (IPD) model--one where weapons use is simulated and one where it is not. We then measured the performance of 25 IPD strategies to evaluate the effects of weapons use on them. We found that cooperative strategies performed significantly better, and non-cooperative strategies significantly worse, under simulated weapons use. Importantly, the performance of an 'Always Cooperate' IPD strategy, equivalent to that of 'strong reciprocity', improved significantly more than that of all other cooperative strategies. We conclude that the development of extra-somatic weapons throws new light on the evolution of human altruistic and cooperative behaviour, and particularly 'strong reciprocity'. The notion that distinctively human altruism and cooperation could have been an adaptive trait in a past environment that is no longer evident in the modern world provides a novel addition to theory that seeks to account for this major evolutionary puzzle.
This paper reviews economic evaluations of motorcycle helmet interventions in preventing injuries. A comprehensive literature review focusing on the effectiveness of motorcycle helmet use, and on mandatory helmet laws and their enforcement was done. When helmet laws were lifted between 1976-80, 48 states within the U.S.A. experienced a cost of $342,047 per excess fatality of annual net savings. Helmet laws in the USA had a benefit-cost ratio of 1.33 to 5.07. Taiwan witnessed a 14% decline in motorcycle fatalities and a 22% reduction of head injury fatalities with the introduction of a helmet law. In Thailand, where 70-90% of all crashes involve motorcycle, after enforcement of a helmet law, helmet-use increased five-fold, the number of injured motorcyclists decreased by 33.5%, head injuries decreased by 41.4%, and deaths decreased by 20.8%. There is considerable evidence that mandatory helmet laws with enforcement alleviate the burden of traffic injuries greatly. For low and middle-income countries with high rates of motorcycle injuries, enforced, mandatory motorcycle helmet laws are potentially one of the most cost-effective interventions available.