John Carson

Ancient women’s elbow grease

The prehistoric transition from hunting and gathering to agriculture meant more sedentary lifestyles for ancient humans. Male skeletons from central Europe show gradually declining mobility and bone strength between the adoption of agriculture, ~5,300 years bc, and the late Iron Age, ad 850. However, until now it has been difficult to discern patterns of change in female skeletons, because of females’ lower physiological response to manual loading and the lack of a modern comparison dataset. A study by Alison Macintosh of the University of Cambridge and colleagues redresses this imbalance by comparing measurements from prehistoric female skeletons from across central Europe to the bones of modern female athletes and non-athletes. The authors look at crosssectional rigidity and shape of the tibia and the humerus, as a proxy for the amount and intensity of activity done with the legs and arms, respectively. Tibial rigidity is not significantly different overall between prehistoric and modern women, suggesting an early transition towards more sedentary female lifestyles since the adoption of agriculture in central Europe. However, humeral rigidity in the 5,500 years between the Neolithic and the Bronze Age was significantly greater than in the average modern woman and most comparable to athletic rowers. This suggests that hard physical labour using mostly the upper body, such as farm work and grinding cereal grains, was a large component of prehistoric, central European women’s lifeways; unlike males, who do not show evidence of enhanced upper limb bone strength. The research reveals more about the history of a gendered division of labour and demonstrates the need to increase femalespecific reference data and investigations to tell the often-distinct story of female lives over human history.

Middle Stone Age thinking

The earliest Homo sapiens in Africa (dated 200–350 thousand years ago (ka)) had brains comparable in size to modern humans and their fossil remains are often associated with the emergence of the more refined and diverse Middle Stone Age (MSA) stone-tool technologies. However, despite the apparent technological innovation, there is surprisingly little archaeological evidence from this early period for the types of complex behaviours that we might associate with modern humans, such as symbolic thought, long-term planning and extended social networks. A paper by Alison Brooks, of George Washington University, and colleagues describes archaeological evidence for complex behaviour as early as ~300 ka at the MSA Olorgesailie Basin site in southern Kenya. The site provides some of the earliest evidence to date for long-distance transport of obsidian for tool making and processing of decorative red pigments. The emergence of MSA technology on this site, therefore, appears to mark a transition to expanding social and trading networks and potentially to symbolic or ritualistic behaviour. A linked paper by Richard Potts, of the Smithsonian Institute, National Natural History Museum, and colleagues indicates that the transition from earlier Acheulean tools to MSA technology occurred in an increasingly variable and unpredictable climate and landscape. This lends evidence to the hypothesis that H. sapiens expanded its behavioural repertoire partially in response to shifting environments, and contextualizes the biological–behavioural– environmental feedbacks active in human evolution.

Human legacy in cloud forest

The arrival of Europeans in the New World in 1492 ad and the subsequent collapse of indigenous populations marked the start of profound cultural, demographic and ecological changes — including in the great forest landscapes of the Andes and Amazonia. Evidence shows that parts of these forests had large indigenous populations, but the extent of their impact on and management of the environment remains uncertain. Nicholas Loughlin and colleagues present a palaeoecological lake record that traces human–environment interactions in the Andean–Amazonian forest corridor — an ancient Incan trade route — across centuries from pre-European times. They find that indigenous populations extensively burned and managed the landscape around the lake for maize agriculture and evidently had an even greater impact on its structure and ecology than later Colonial settlement or modern-day cattle ranches. The mature mountain cloud forest encountered by later European settlers in the nineteenth century was therefore not pristine, but represented a regrowth following indigenous population collapse, probably shaped by the long history of human management. Linking palaeoecological and historical accounts is a powerful way to reveal complex histories of human–environment interactions. Future work will need to determine whether the intensive impacts seen at this site are typical of the wider region.

Opioids on the dark web

The United States is facing an epidemic of opioid addiction. One response has been to restrict the legal supply of drugs, which has led to a reduction in prescriptions. However, the impact of such supply interventions on drug purchasing overall — especially through illicit channels — is uncertain. In a new study by James Martin, from Swinburne University of Technology, and colleagues, the authors analysed the impact of a US legal ruling in 2014 — which reclassified and restricted legal access to the most commonly prescribed opioids — on the sales of prescription medicines in illegal cryptomarkets. These function similarly to legal online markets such as eBay, but on the darknet. The authors analysed data on the number of for-sale listings and estimated purchases of prescription opioids from 31 cryptomarkets over a three-year period that spanned the legal change. Listings and sales for prescription opioids in the US markets increased significantly, compared with other types of drugs and opioids in other countries, after the legal ruling in 2014. In July 2016, prescription opioids accounted or 13% of all illicit drugs purchased in the United States on the cryptomarkets, but a time series analysis suggests that without the legal change, this would have been only 6%. The largest increases in sales were seen in the most potent opioids. While the authors acknowledge that their evidence is not definitively causal, it suggests that restricting the legal purchase of opioids pushes consumers towards illegal markets, which are a gateway for some to more powerful drugs, in an unregulated environment.

To conceal or confess

Security organizations and political departments have the ability to exercise great power on our behalves. It is in the public’s interest to ensure that these bodies do not overreach their powers. However, when institutions have the option to conceal their actions, why would their leaders voluntarily submit to accountability and tough penalties? In a new paper by William Spaniel and Michael Poznansky of the University of Pittsburgh, the authors model executives’ incentives to impose voluntary regulation and sanctions. In the model, executives choose a regulatory regime (to conceal or be open) based on the potential cost of a successful investigation by a watchdog or whistleblower. If the ‘natural’ cost of being caught is low — reflected in public mood or the legal status quo — then the executive has little incentive to increase the cost of violations. However, if the potential repercussions are higher, executives benefit from setting high internal costs for violations and encouraging whistleblowing, because they disincentivize the costly wrong action in the first place and risk only minor reputational costs from an investigation. The authors illustrate their point with the US President Gerald Ford’s dilemma in the 1970s, when public disapproval of covert government operations increased their political cost. The work cautions us that changes in public mood can open the door to erode established regulatory structures and see a return to the use of covert actions.

Exercise for a healthy mind

Regular exercise has been linked to numerous physical health benefits and reduced mortality overall. Exercise may also improve mental health, but the evidence to date has been unclear. In a paper by Sammi Chekroud, of University of Oxford, and colleagues, the authors conducted a cross-sectional analysis of health and lifestyle data from more than one million US adults over three years. Their analysis compared self-reported occurrences of bad mental health between individuals who did and did not exercise and also examined the relationship with different exercise regimes. Participant data was carefully matched to control for sociodemographics and other potential confounding factors. The study found on average a 43% reduction or 1.49 fewer days of poor mental health per month in individuals who exercised. Although all types of exercise were associated with lower mental health burden, the largest association was with team sports and seemed optimal for 3–5 sessions of 45 minutes per week; more exercise is not necessarily better, as there was no incremental benefit to exercising beyond 90 minutes, 5 times a week. These findings will lend greater confidence and specificity in developing physical exercise as a treatment for a variety of mental health issues.

Teen friends a genetic match

Human social pairs — such as spouses and adult friends — are often more similar genetically than randomly selected individuals. The resulting genetically homogeneous social networks can impact the direction of multiple life outcomes, such as health choices and educational attainment. Adolescence is a particularly formative life stage, where the potential for friends to influence development is high, and so it is important to understand what role genetic assortment might play in directing this development. Benjamin Domingue and colleagues examined evidence for genetic similarity among teenage groups of friends in a US population and for potential sociogenetic influences, whereby an individual’s developmental outcomes could be influenced by the genes of their friends and peers. The authors compared the genetic and social network data of 5,500 individuals from the National Longitudinal Study of Adolescent to Adult Health. They found significant genetic similarity overall between friend pairs and positive correlations based on genes specifically related to body mass index and educational attainment, but not height. Similar results were found between school mates in general, suggesting that, while people may choose genetically similar friends based on shared characteristics, institutions such as schools may also stratify the population into more homogenous subgroups. Finally, the study found evidence for a socio-genetic effect, with the genes of friends and schoolmates significantly predicting an individual’s level of educational attainment later in life. These findings are a caution that potential socio-genetic effects should be taken into account more in genome-wide association studies. They also highlight a way to parse the significance of genetic and environmental influences in studies of social development.

Pre-pregnancy health

Encouraging people to practice healthy lifestyles before pregnancy may ensure the long-term health of their children. However, there is a need to identify which types of interventions will be most effective and by what means they are best delivered at different life stages. Mary Barker, of the University of Southampton, and colleagues evaluated 14 published studies that aimed to improve preconception nutrition through nutritional supplementation, cash incentives or behaviour change interventions. They then identified which intervention pathways are most likely to be effective at different stages in people’s lives, in accordance with their changing life motivations. Based on these analyses, the authors advocate a combined strategy of encouraging healthy nutrition in those planning pregnancy, via traditional health services, and informing and supporting the public more broadly, via a mix of channels, to lay the groundwork for healthy pregnancies in future. Social marketing campaigns that provide only health information have not been effective in improving outcomes for all socioeconomic groups. Instead, the authors argue for a broader social movement that will also provide the resources to enact change and instil the motivation among citizens by making the link between preconception health and children’s life outcomes public knowledge. Tactics from marketing brand development could help to form more effective motivational campaigns. Such campaigns also need to involve industry and leverage its massive influence on consumer behaviour. These goals may be best achieved by establishing an advocacy coalition that will place preconception health on the political agenda.

Savings on healthcare

Encouraging healthcare providers to coordinate and share resources may reduce the costs of care provision. The Medicare Shared Savings Program (MSSP) was introduced in the United States to enable coordination between accountable care organizations (ACOs) and to incentivize cost savings in fee-for-service (payments made per treatment) Medicare. Previous assessments suggest that the MSSP has achieved only small savings that are offset by bonuses paid out to ACOs for meeting MSSP targets. However, these assessments did not have a reliable way to estimate potential spending in the absence of a savings programme. J. Michael McWilliams, of Harvard Medical School, and colleagues address this limitation using Medicare claim and enrolment data from 2009–2015. The authors compare how much ACOs spent on patients before and after they entered the MSSP, and how much they spent compared with providers not in the MSSP. The difference-in-difference analysis reveals a significant reduction in spending for ACO physician groups, amounting to a net saving of

Greater suicide in LGBT youth

264.4 million for Medicare by 2015. For larger, hospital-integrated ACOs, however, the savings were modest and offset by bonuses. These findings suggest that sharedsavings contracts like the MSSP offer attractive and achievable cost-saving incentives for physician groups, but not for larger, hospital-based consortia.