Faculty/School

Faculty of Science

School of Mathematical Sciences

Topic status

We're looking for students to study this topic.

Research centre

Primary Supervisor

Other QUT supervisors

Dr Maria Kleshnina
Position
ARC DECRA Fellow
Division / Faculty
Faculty of Science

Overview

Can we understand horizontal identity using gene-culture evolution models?

Some human behaviours seem hard to square with biology. The 2019 Christchurch mosque shooter is currently serving a life sentence; nevertheless, a network of online communities venerate him, providing support for people who aspire to carry out similar attacks and producing media to inspire it. At least 27 attacks since then have been partly inspired by the Christchurch shooter, every one ending in the perpetrator's imprisonment or death. Here lies the puzzle: if we expect living things to be shaped by selection for survival and reproduction, then how does a behaviour that reliably ends in the individual's death and imprisonment persist, let alone grow and spread?

One might view this example as an aberration; however, cultures are full of roles that ask people to give up survival or reproduction in the service of an idea, and not all of them are sinister. For example, many religious traditions recognise a role for people who take vows of poverty and chastity to live a life of service. Meanwhile, the service they perform promotes the ideals of the religion and the prestige of the role itself. The structure here is the same although the valence differs: the individual's own reproductive success is given up, while what propagates is the idea. This inversion --- fitness accruing to the idea rather than the person --- is what this project sets out to model. The work itself is mathematical: we will be building and analysing models of how traits spread, not studying extremist content.

One lens for understanding these behaviours is what Andrew Solomon calls "horizontal identity": a way of being that, although it might be initiated biologically, is largely acquired not from one's parents but from peers. We extend the idea to a social role and norms transmitted along both routes at once: vertically, from one generation to the next; and horizontally between peers who recruit and reinforce one another. The shooter network and the religious order are both horizontal identities in this sense.

Modelling these scenarios is difficult. Evolutionary game theory often assumes selection is weak, e.g., replicator dynamics assumes the effect of the behaviour is small relative to background fitness determinants. However, that assumption fails when a strategy drives the actor's reproduction to zero. To handle strong selection acting alongside cultural transmission, this project will investigate a phenogenotype framework, which keeps track of both what someone inherits biologically and what they pick up culturally without assuming the effect on biological fitness is small.

This project will provide an authentic research experience. You will not be handed a predefined task or a model to run. Your supervisor is in the early stages herself, which means she will be reading the literature and testing the modelling techniques alongside you. The concrete output for your final presentation will be a literature survey: a review and synthesis of the relevant modelling approaches. However, there is room for you to choose a model that interests you and put it through its paces: map out which scenarios it handles well and where it breaks down, and build a small model of your own. As noted, the work is mathematical --- reading modelling literature and testing models --- but there is room for you to investigate whichever flavour of "horizontal identity" interests you.

What you'll need:

  • Familiarity with dynamical-systems models (e.g., Lotka–Volterra models)
  • The ability to analyse them: finding a model's steady states and determining their stability
  • Proficiency with Python or MATLAB/Octave
  • Some experience investigating dynamical models numerically (preferred but not essential)

What you'll gain:

  • First-hand experience of open-ended research
  • Practical skill in building and analysing models
  • A grounding in the dual-inheritance / cultural-evolution literature

Further reading:

Research engagement

literature review, modelling

Research activities

Reading literature and exploring models

Research skills

Experience with open-ended research, building analysing models, grounding in cultural evolution modelling literature

Outcomes

Literature survey + potentially analysis of one small model (student's choice)

Skills and experience

Familiarity with dynamical systems and Python or MATLAB

Start date

2 November, 2026

End date

19 February, 2027

Location

QUT Gardens Point

Additional information

https://nadiah.org/

Keywords

Contact

Nadiah Kristensen

0403 796 462

n2.kristensen@qut.edu.au