From brains to bears. understanding brain size evolution: causes, costs and benefits
Developmental and energetic costs result in brains being expensive organs to grow and maintain, yet large brains have evolved in many mammalian species. The adaptive value of increased brain size has come under scrutiny over the past few decades and despite considerable research effort, much uncerta...
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| Format: | Thesis |
| Language: | English |
| Published: |
2022
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| Online Access: | http://usir.salford.ac.uk/id/eprint/64518/ https://usir.salford.ac.uk/id/eprint/64518/1/Masters%20Thesis_R1_HRC.pdf |
| Summary: | Developmental and energetic costs result in brains being expensive organs to grow and maintain, yet large brains have evolved in many mammalian species. The adaptive value of increased brain size has come under scrutiny over the past few decades and despite considerable research effort, much uncertainty remains regarding: (i) the selective pressures responsible and (ii) the potential benefits that big brains provide. Here, both topics are investigated. Firstly, the influence of social, ecological and life-history traits were assessed on whole and regional brain size in two well-studied orders: Primates and Carnivora. In primates, consistent associations are found between brain size and dietary factors, such as dietary breadth; however, evidence is also found indicating sociality as a selection pressure driving brain size. In carnivores, evidence suggests ecological variables, most notably home range size, is influencing brain size, whereas no support is found for the social brain hypothesis. Life-history associations reveal complex selection mechanisms counterbalance the costs associated with expensive brain tissue through extended developmental periods, reduced fertility and extended maximum lifespan. Secondly, to better understand the proposed benefits afforded by encephalisation, the cognitive abilities of 17 captive European brown bears (Ursus arctos arctos) were tested via two behavioural problem-solving trials. Results revealed evidence of trial-and-error learning; however, two juveniles appeared to acquire an association between the latch and access to the box, suggesting some individuals have potential to adopt successful strategies and draw perceptive associations. Individual variation in motivation levels appears to be an important factor influencing cognitive performance. The bears failed to spontaneously use a tool but still managed to retrieve the food reward, instead using alternative techniques. Analyses revealed both age and sex (using female as the reference category) to be negatively associated ... |
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