White Rose University Consortium logo
University of Leeds logo University of Sheffield logo York University logo

The evolution of sibling interactions in humans

Nitsch, Aïda (2014) The evolution of sibling interactions in humans. PhD thesis, University of Sheffield.

[img] Text
Restricted indefinitely.

Request a copy


Studying the fitness consequences of living in the presence of siblings at different life history stages, and thus how siblings differ in their fitness maximising strategies, is crucial for understanding the evolution of family dynamics. Using a large demographic dataset from historical Finland, I investigate the effects of sibling interactions on key life history traits, including dispersal phenotype (i.e. dispersing or remaining philopatric) and its direct and indirect fitness outcomes. First, I highlight opposite effects of sibling interactions depending on life history stage, and show that overall lifetime reproductive success was reduced by the presence of same-sex elder siblings, but increased by the presence of opposite-sex elder siblings (Chapter 2). These results suggest that individuals may switch their fitness maximising strategy in different life history stages. I then show that dispersal patterns are strongly influenced by intra-sex competition (over land resources for males and mating opportunities for females) with later born, disadvantaged siblings being more likely to disperse (Chapter 3). However, I find no evidence that later born children with lower access to parental resources benefitted more from dispersing than did first borns (Chapter 4). Finally, I investigate potential indirect fitness benefits of helping behaviour provided by relatives who remain philopatric and single, but I do not find evidence for alloparenting effects (Chapter 5). Overall, these results suggest that differential access to parental resources could have qualitative as well as quantitative consequences on the fitness maximising strategies of siblings with different access to resources, namely that first born offspring gained fitness both directly and indirectly, whereas later born, disadvantaged siblings only seemed to invest in their direct fitness. This thesis provides a substantial step towards understanding sibling interactions over the entire life-course rather than only focusing on early-life consequences, and stresses the need for more long-term studies of sibling interactions.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Animal and Plant Sciences (Sheffield)
Depositing User: Aïda Nitsch
Date Deposited: 27 Mar 2015 09:03
Last Modified: 27 Mar 2015 09:03
URI: http://etheses.whiterose.ac.uk/id/eprint/8206

Please use the 'Request a copy' link(s) above to request this thesis. This will be sent directly to someone who may authorise access.
You can contact us about this thesis. If you need to make a general enquiry, please see the Contact us page.

Actions (repository staff only: login required)