Kinship dynamics: patterns and consequences of changes in local relatedness

Abstract

Mounting evidence suggests that patterns of local relatedness can change over time in predictable ways, a process termed kinship dynamics. Kinship dynamics may occur at the level of the population or social group, where the mean relatedness across all members of the population or group changes over time, or at the level of the individual, where an individual's relatedness to its local group changes with age. Kinship dynamics are likely to have fundamental consequences for the evolution of social behaviour and life history because they alter the inclusive fitness payoffs to actions taken at different points in time. For instance, growing evidence suggests that individual kinship dynamics have shaped the evolution of menopause and age-specific patterns of helping and harming. To date, however, the consequences of kinship dynamics for social evolution have not been widely explored. Here we review the patterns of kinship dynamics that can occur in natural populations and highlight how taking a kinship dynamics approach has yielded new insights into behaviour and life-history evolution. We discuss areas where analysing kinship dynamics could provide new insight into social evolution, and we outline some of the challenges in predicting and quantifying kinship dynamics in natural populations.

Social ageing: exploring the drivers of late-life changes in social behaviour in mammals

“…Social effort given is likely to be similar in magnitude but more widely distributed for dispersers. [155,156,158] age Figure 1. Challenges to disentangling explanations for age-related changes in adult social behaviour.…”

“…In this way, within-individual declines in sociality with age might occur as a result of population-level demographic changes. Local demography can also affect how average relatedness to potential social partners changes with age, which might result in advantageous within-individual shifts in social behaviour because individuals may gain indirect fitness by supporting relatives [ 155 ]. Theoretical models have demonstrated that changing patterns of relatedness can favour different patterns of helping and harming behaviour with age [ 156 ], which, in some specific contexts, is suggested to play an important role in selecting for late-life helping behaviour, such as the cessation of females' reproduction in favour of promoting their offspring's reproductive success [ 42 , 157 ].…”

“…Kinship dynamics predict different patterns of age-related social behaviour depending on patterns of mating and individual dispersal. When mating occurs within social groups, mean relatedness to the group remains relatively constant for members that do not disperse at sexual maturity as relatives die or emigrate and are replaced by newly born relatives or immigrants [ 155 , 156 ]. As a result, we should expect that levels of social affiliation and social differentiation should be fairly stable with age for philopatric individuals.…”

“…As a result, we should expect that levels of social affiliation and social differentiation should be fairly stable with age for philopatric individuals. For dispersing individuals, mean relatedness to group members is expected to be low when they first join a group and to increase with age as they start to contribute offspring [ 155 , 156 ]. Dispersed individuals might therefore be expected to experience and engage in less aggression as they age and have larger and less differentiated social networks.…”

Volatile social environments can favour investments in quality over quantity of social relationships

“…behaviour is generally starting to realize that the social environment is very likely different for individuals differing in their age;Croft et al 2021 discuss this with respect to kinship (see alsoRodrigues 2018). Our work shows that the social state, i.e.…”