Professional religious specialists centralised religious authority in early human societies and represented some of the earliest instances of formalised social leadership. These individuals played a central role in the emergence of organised religion and transitions to more stratified human societies. Evolutionary theories highlight a range of environmental, economic and social factors that are potentially causally related to the emergence of professional religious specialists in human history. There remains little consensus over the relative importance of these factors and whether professional religious specialists were the outcome or driver of increased socio-cultural complexity. We built a global dataset of hunter–gatherer societies and developed a novel method of exploratory phylogenetic path analysis. This enabled us to systematically identify the factors associated with the emergence of professional religious specialists and infer the directionality of causal dependencies. We find that environmental predictability, environmental richness, pathogen load, social leadership and food storage systems are all correlated with professional religious specialists. However, only food storage is directly related to the emergence of professional religious specialists. Our findings are most consistent with the claim that the early stages of organised religion were the outcome rather than driver of increased socio-economic complexity.

Kinship is a fundamental and universal aspect of the structure of human society. The kinship category of ‘grandparents’ is socially salient, owing to grandparents’ investment in the care of the grandchildren as well as to older generations’ control of wealth and cultural knowledge, but the evolutionary dynamics of grandparent terms has yet to be studied in a phylogenetically explicit context. Here, we present the first phylogenetic comparative study of grandparent terms by investigating 134 languages in Pama–Nyungan, an Australian family of hunter–gatherer languages. We infer that proto-Pama–Nyungan had, with high certainty, four separate terms for grandparents. This state then shifted into either a two-term system that distinguishes the genders of the grandparents or a three-term system that merges the ‘parallel’ grandparents, which could then transition into a different three-term system that merges the ‘cross’ grandparents. We find no support for the co-evolution of these systems with either community marriage organisation or post-marital residence. We find some evidence for the correlation of grandparent and grandchild terms, but no support for the correlation of grandparent and cross-cousin terms, suggesting that grandparents and grandchildren potentially form a single lexical category but that the entire kinship system does not necessarily change synchronously.

Germination timing is a key transition of life history. It not only links subsequent life-history traits, such as plant height and flowering time, but also provides a link to the previous generation through the influence of the maternal environment. Environmental factors may mediate these key links, and consequences of this process may influence species regeneration and dispersal. However, little is known about how environmental factors mediate these key links. Here, germination timing under high (natural light) and low light treatments was estimated for 476 angiosperm species of the eastern Tibetan Plateau grasslands. Furthermore, we used standard (std) and phylogenetic (phy) comparative methods to test if germination timing was associated with plant height, flowering time and maternal habitats under both light treatments. Germination timing was positively correlated with plant height only in low light in std-methods. Germination timing was associated with onset of flowering in both light treatments in std-methods, but only in low light when using phy-methods. Germination timing was positively correlated with elevation only in low light when using both comparative methods. Germination timing was correlated with water in maternal habitat only in high light when using both comparative methods. Germination timing was associated with light in maternal habitat in both light treatments in std-methods, but only in high light when using phy-methods. In summary, light-dependent associations of germination timing with subsequent life-history traits and maternal habitats may influence the probability of plant species life-cycle completion and influence distribution and dispersal of plant species in natural plant communities.