Background: The coronavirus disease 2019 (COVID-19) pandemic and mitigation measures are likely to have a marked effect on mental health. It is important to use longitudinal data to improve inferences. Aims: To quantify the prevalence of depression, anxiety and mental wellbeing before and during the COVID-19 pandemic. To identify groups at risk of depression and/or anxiety during the pandemic. Methods: Data were from two generations of the Avon Longitudinal Study of Parents and Children (ALSPAC): the index generation (ALSPAC-young, n=2850, mean age=28), parent's generation (ALSPAC-parents, n=3720, mean age=59), and Generation Scotland (GS, n=4233, mean age=59). Depression was measured using the Short Mood and Feelings Questionnaire (SMFQ) in ALSPAC and the Patient Health Questionnaire (PHQ-9) in GS. Anxiety and mental wellbeing were measured using the Generalised Anxiety Disorder Assessment (GAD-7) and the Short Warwick Edinburgh Mental Wellbeing Scale. Results: Depression during COVID-19 was similar to pre-pandemic levels in ALSPAC-young, but those experiencing anxiety almost doubled during COVID-19: 24% (95% CI: 23%, 26%) compared to pre-pandemic levels of 13% (95% CI: 12%, 14%). In both ALSPAC and Generation Scotland, anxiety and depression during COVID-19 was greater in younger members, in women, in those with preexisting mental/physical health conditions, and in individuals in socioeconomic adversity, even when controlling for pre-pandemic anxiety and depression. Conclusions: These results provide evidence for increased anxiety in young people that is coincident with the pandemic. Specific groups are at elevated risk of depression and anxiety during COVID-19. This is important for planning mental health provisions now and for long-term impact beyond this pandemic.

The social organization of mobile hunter-gatherers has several derived features, including low within-camp relatedness and fluid meta-groups. Although these features have been proposed to have provided the selective context for the evolution of human hypercooperation and cumulative culture, how such a distinctive social system may have emerged remains unclear. We present an agent-based model suggesting that, even if all individuals in a community seek to live with as many kin as possible, within-camp relatedness is reduced if men and women have equal influence in selecting camp members. Our model closely approximates observed patterns of co-residence among Agta and Mbendjele BaYaka hunter-gatherers. Our results suggest that pair-bonding and increased sex egalitarianism in human evolutionary history may have had a transformative effect on human social organization.

Although multilevel sociality is a universal feature of human social organization, its functional relevance remains unclear. Here, we investigated the effect of multilevel sociality on cumulative cultural evolution by using wireless sensing technology to map inter- and intraband social networks among Agta hunter-gatherers. By simulating the accumulation of cultural innovations over the real Agta multicamp networks, we demonstrate that multilevel sociality accelerates cultural differentiation and cumulative cultural evolution. Our results suggest that hunter-gatherer social structures [based on (i) clustering of families within camps and camps within regions, (ii) cultural transmission within kinship networks, and (iii) high intercamp mobility] may have allowed past and present hunter-gatherers to maintain cumulative cultural adaptation despite low population density, a feature that may have been critical in facilitating the global expansion of Homo sapiens.