The Panglossian Paradigm revisited : The role of non adaptive mechanisms in hominid brain and body size evolution

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dc.contributor.author Spocter, Muhammad Aadil
dc.date.accessioned 2009-01-21T08:06:39Z
dc.date.available 2009-01-21T08:06:39Z
dc.date.issued 2009-01-21T08:06:39Z
dc.identifier.uri http://hdl.handle.net/10539/5955
dc.description.abstract The largely dominant adaptationist argument is currently used as the framework within which hominid brain evolution is explained; however these adaptationist explanations are inherently problematic and only suffice to ‘clutter’ our knowledge of the possible causes of hominid brain evolution. This study addresses the caveats observed in the fossil record and aims to assess the relative influence of structural laws of form, phylogenetic constraints, and adaptive factors during the course of primate and hominid brain evolution. A combination of methods such as variance partitioning, phylogenetic regression procedures and path analysis indicate that constraints have played a critical role in the scaling attributes of the primate and hominid brain. In particular, developmental constraints governing the scaling attributes of the skull and body are shown to explain up to 50 % of the variation in body mass whereas phylogenetic constraints are purported to have played a lesser role (i.e. 0.8 -3.6 %). In addition, the scaling attributes of neural and non-neural components of the cranial vault suggest a highly constrained suite of traits and suggest that as much as 96 % of the variation in both brain mass and residual endocranial space may be explained by correlated scaling with the cranial vault. Constraints are observed to be far more pliable than traditionally thought – a feature highlighted by intraspecific analyses of scaling attributes in humans. Low regression coefficients typical reported for intraspecific curves are shown to arise during development as greater variation in body parameters is allowed with advancing age. Grade shifts in the scaling of brain and body size for primates and other mammalian orders is also emphasised by this current study and it is argued that correlated changes between the brain and body size may not necessarily impact upon the ‘complexity’ of the neural system as the functional integrity may be maintained via higher output states initiated at certain levels of organisation such as at the level of the cortical area. Although constraints should rightfully be given greater coverage in explanations concerning hominid brain expansion, it is only through implementation of research protocols that take a pluralistic approach to an understanding of the role of both constraints and adaptation in the formation of the brain that our interpretation of the likely mechanism for hominid brain expansion may be understood. en
dc.language.iso en en
dc.subject hominid en
dc.subject brain evolution en
dc.subject body size en
dc.subject constraints en
dc.title The Panglossian Paradigm revisited : The role of non adaptive mechanisms in hominid brain and body size evolution en
dc.type Thesis en


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