Year: 2024
Type: dissertation
Abstract: Group living and cooperation are deeply entwined and we are yet to explain their diversity and distribution across the animal kingdom. Relatedness facilitates the evolution of group living and cooperation as kin provide direct and indirect fitness benefits whereas non-kin only provide direct benefits. Yet, available data from societies that feature multiple individuals of the same sex suggest that living with same-sex non-kin is not rare, even though individuals would get larger fitness from living and cooperating with same-sex kin. In this thesis, I provide foundational knowledge about which species of mammals live with non-kin, why they do that and what consequences that has for the social structure of societies. First, I assembled a dataset of mammalian kinship composition, which is a group-level attribute of the extent to which groups are constituted by kin, non-kin or both. Approximately half of the 18 species in the dataset lived with kin and non-kin, while the other half lived only with kin. Then, I used agent-based models to formally assess how group-augmentation via non-kin immigration constitutes a possible route for the evolution of societies that feature same-sex non-kin. The models illustrated situations in which the benefits of living in optimal group size via non-kin immigration outweigh the costs of living with non-kin. Using an analytical model, I also showed that living with non-kin is beneficial when the mean relatedness between kin is low and when non-kin provide substantially more direct fitness benefits than kin. Finally, using empirical behavioural and pedigree data from a population of macaques, I found no evidence that kinship composition influences social structure. However, agent-based models showed that such a relationship is expected to exist but may only be detectable with larger sample size and variance in kinship composition. Overall, my work shows that it is not rare for mammals to live with non-kin, illustrates how living with non-kin might evolve, and showed how kinship composition might influence social structure, further corroborating the idea that direct benefits work together with indirect benefits to explain the diversity of group-life and cooperative behaviour observed across mammalian societies.
Author: A Seno Pereira (21971309)
Language: English
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W6982722965