Our results provide evidence that the hunting and gathering foraging strategy involves high levels of MVPA, supporting the evolutionary medicine model for the relationship between MVPA and cardiovascular health.

If individuals will cooperate with cooperators, and punish non-cooperators even at a cost to themselves, then this strong reciprocity could minimize the cheating that undermines cooperation. Based upon numerous economic experiments, some have proposed that human cooperation is explained by strong reciprocity and norm enforcement. Second-party punishment is when you punish someone who defected on you; third-party punishment is when you punish someone who defected on someone else. Third-party punishment is an effective way to enforce the norms of strong reciprocity and promote cooperation. Here we present new results that expand on a previous report from a large cross-cultural project. This project has already shown that there is considerable cross-cultural variation in punishment and cooperation. Here we test the hypothesis that population size (and complexity) predicts the level of third-party punishment. Our results show that people in larger, more complex societies engage in significantly more third-party punishment than people in small-scale societies.

The Hadza are hunter-gatherers in Tanzania. Their diet can be conveniently categorized into five main categories: tubers, berries, meat, baobab, and honey. We showed the Hadza photos of these foods and asked them to rank them in order of preference. Honey was ranked the highest. Tubers, as expected from their low caloric value, were ranked lowest. Given that tubers are least preferred, we used kilograms of tubers arriving in camp across the year as a minimum estimate of their availability. Tubers fit the definition of fallback foods because they are the most continuously available but least preferred foods. Tubers are more often taken when berries are least available. We examined the impact of all foods by assessing variation in adult body mass index (BMI) and percent body fat (%BF) in relation to amount of foods arriving in camp. We found, controlling for region and season, women of reproductive age had a higher %BF in camps where more meat was acquired and a lower %BF where more tubers were taken. We discuss the implications of these results for the Hadza. We also discuss the importance of tubers in human evolution.

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We analyse generosity, second-party ('spiteful') punishment (2PP), and third-party ('altruistic') punishment (3PP) in a cross-cultural experimental economics project. We show that smaller societies are less generous in the Dictator Game but no less prone to 2PP in the Ultimatum Game. We might assume people everywhere would be more willing to punish someone who hurt them directly (2PP) than someone who hurt an anonymous third person (3PP). While this is true of small societies, people in large societies are actually more likely to engage in 3PP than 2PP. Strong reciprocity, including generous offers and 3PP, exists mostly in large, complex societies that face numerous challenging collective action problems. We argue that 'spiteful' 2PP, motivated by the basic emotion of anger, is more universal than 3PP and sufficient to explain the origins of human cooperation.

The foraging and food sharing of hunter-gatherers have provided the backdrop to several different evolutionary hypotheses about human life history. Men's foraging has often been characterized as primarily targeting animals, with high variance and high rates of failure. To the best of our knowledge, however, there are as yet no quantitative studies reporting the amounts of food that men eat while foraging, before returning to their households either empty-handed or with foods. Here, we document this under-reported part of forager's dietsmen's eating while out of camp on foray. Our dataset consists of 146 person/day follows (921 hours total) collected over a period of 12 years (from 2001-2013, including 12 camps). Hadza men consumed a substantial amount of food while out of camp foraging. Men did more than just snack while out of camp foraging, they consumed a mean of 2,405 kilocalories per foray, or approximately 90% of what is estimated to be their mean daily Total Energy Expenditure (TEE). The characterization of men's foraging strategies as "risky", in terms of calorie acquisition, may be exaggerated. Returning to camp empty-handed did not necessarily mean the forager had failed to acquire food, only that he failed to produce enough surplus to share. Surprisingly, the vast majority of the kilocalories eaten while out of camp came from honey (85%). These observations are relevant to evolutionary theories concerning the role of male provisioning. Understanding primary production and consumption is critical for understanding the nature of sharing and the extent to which sharing and provisioning supports reproduction in hunter-gatherers.

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