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Evolution of Self-Organised Division of Labour in Social Insects

Scholtens, E. (2010) Evolution of Self-Organised Division of Labour in Social Insects. Master's Thesis / Essay, Artificial Intelligence.

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One of the factors attributed to the success of humans is the ability to divide work among specialised groups. This division of work between (specialised) groups is known as division of labour and can lead to a large efficiency increase for the whole group. The level of division of labour is determined by the degree to which individuals stick to tasks over time. Division of labour is found in humans, ants, social bees, wasps, and naked mole rats among others. Current models on division of labour in insects focus on how interactions of individuals lead to division of labour by self-organisation. In this thesis two critiques on current models are given. First, often the ability of a colony to change worker-ratios is not investigated. Second, hardly any model looks at how self-organised behaviours, leading to division of labour, could have been shaped by evolution. These two points are the focus of this thesis. The first model that is investigated is the response-threshold model. Although division of labour is obtained, it is not an emergent property, but a result of a designed mechanism. The second model is an evolutionary model, where individuals have preferences, which determine the probability that an individual will work in response to external stimuli. When this model is investigated a surprising property of the model is uncovered. In equilibrium, workers cannot influence the tasks they work at, despite their preferences. This is a consequence of assuming a closed world, with a tight coupling between a colony and the resources. A third model is presented with a behaviour mechanism based on a feed-forward neural network, where weights are evolved instead of being chosen by a designer. This mechanism is more flexible and decreases the coupling between a colony and the resources. A fitness function is chosen that rewards certain worker ratios within a colony. Optimal work-allocation ratios are quickly evolved, but with low levels of division of labour. If a switching cost is introduced, high levels of division of labour evolve. In this scenario, it turns out that the mode of inheritance becomes a factor. Colonies with linked genes are not able to evolve the required ratios, while colonies with full recombination are able to evolve optimal work ratios, despite disruptive recombination. In conclusion, the models show that the mode of inheritance is a key factor for evolving specific worker ratios and that division of labour could have evolved due to a switching cost, that is naturally present in a spatial setting.

Item Type: Thesis (Master's Thesis / Essay)
Degree programme: Artificial Intelligence
Thesis type: Master's Thesis / Essay
Language: English
Date Deposited: 15 Feb 2018 07:45
Last Modified: 15 Feb 2018 07:45

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