Quantifying gene-culture coevolution

: toward an empirical science of interaction in human dual inheritance

Abstract

Gene-culture coevolution, the reciprocal interactions between genetic and cultural inheritance systems, provides a uniquely powerful framework for understanding human evolution. However, empirical evidence for these coevolutionary processes remains limited, partially due to both conceptual and methodological issues in empirical studies of dual-inheritance. In this thesis, I set out to address some of these issues, in the geographic context of the Pacific Islands. I start by reviewing the gene-culture coevolution literature and propose an expanded conceptual framework distinguishing "narrow" (adaptive) from "broad" (including non-adaptive) coevolution. The remaining chapters are situated within that conceptual set-up and adopt landscape genomic approaches to test for gene-culture interactions in Oceanic populations. First, I investigate temporal patterns of selection in contemporary Hawai’ian genomes using the admixture-aware selection scan method AdaptMix, finding that immune-related selection dominates while evidence for recent culturally-mediated dietary adaptation remains sparse. In the next chapter, I examine genetic associations with traditional subsistence practices across 24 Pacific populations utilising a gene-environment association framework. Using latent factor mixed modelling and partial redundancy analysis, I identify signatures of local adaptation in metabolic pathways showing significant correlations with marine-to-terrestrial dietary gradients. In the final data chapter, I explore non-adaptive evolutionary dynamics by testing whether potentially culturally evolved patterns of conflict have shaped neutral genetic variation in the Pacific and contributed to the regional decline of long-distance voyaging. Using archaeological fortification data and genetic dispersal surfaces generated through the MAPS method, I demonstrate that warfare seems to have substantially reduced gene flow between island populations during the late pre-Contact period, in line with archaeological and anthropological predictions. Collectively, these results reveal multiple pathways through which culture may shape genetic evolution including, but also going beyond, classical selective scenarios. I conclude by discussing how future work, further integrating with theoretical modelling and archaeological data, may build on this approach.

Date of Award	2 Dec 2025
Original language	English
Awarding Institution	University of St Andrews
Supervisor	Kevin Lala (Supervisor), Laura Fortunato (Supervisor) & Luke Rendell (Supervisor)