Lecture 8.docx

Lecture 8: Integrating the Whys – Developing a Comprehensive Framework Diversity and Bringing the 4 Whys Together To Understand the range and diversity of play across the animal kingdom, we need to see how our understanding from all 4 whys can be combined Let’s start by recalling the phylogenetic di...

Lecture 8: Integrating the Whys – Developing a Comprehensive Framework Diversity and Bringing the 4 Whys Together To Understand the range and diversity of play across the animal kingdom, we need to see how our understanding from all 4 whys can be combined Let’s start by recalling the phylogenetic distribution of play The diversity clearly makes finding common developmental patterns, mechanisms and function unlikely What Needs to be Explained? Sporadic emergence of play across the animal kingdom The emphasis on different play types across lineages The changes in complexity within lineages Burghardt has provided a theoretical framework for answering these questions Burghardt’s 2-Pronged Theory When certain environmental and intrinsic factors combine play can emerge Conclusions It is the confluence of enabling factors that make play possible The rarity of such a confluence of fortuitous enabling factors explains the limited emergence of play across the animal kingdom. Some lineages are more likely to combine these factors than others. Initially, play may have minimal costs and no functional benefits, but once present conditions may favor its further evolution Conceptual Components It is useful to categorize the initiating factors and consequences of play into three process levels: We can have primary-process play that grows out of boredom, low behavioral thresholds, immature behavior, excess metabolic energy, and other factors with no necessary long-term effects, good or ill Secondary-Process play that helps maintain the condition of the animal physiologically, behaviorally, and perceptually. For example, physical exercise may be necessary for maintaining cardiovascular functioning and body flexibility, and mental games may aid in slowing the effects of senile dementia Tertiary-Process play that may be crucial for reaching developmental milestones, cognitive accomplishments, social skills, and physical abilities But is the theory supported by empirical findings? Origins of Play Octopus Play Octopus as an empirical test case Object play in octopus Short lived, reclusive, solitary, high risk of predation, early planktonic stage, and short juvenile period. Not a typical candidate for play but, Octopus are large brained Octopus are large brained, play only reported in adults, play is limited to object manipulations and only ever seen in captive animals A large brained, behaviorally flexible animal kept in captivity with food provided and no risk of predation… an animal that can get bored and has the wherewithal to entertain itself So, in fact the octopus fits Burghardt’s model, showing that the factors he identified can promote the emergence of play Play in octopus also shows that it can occur in situations in which no cost is incurred and so no benefits are needed to sustain its continuance Mathematical models also show that it is possible, given the right conditions where costs are low or absent, for primary process play to emerge even in the absence of that play providing benefits Transformation of Play Murid rodents as an empirical test case Mathematical models show how this is possible Simpler play involves less investment and so can evolve more easily than more complex play which requires more investment and so requires greater net gains to evolve What Mechanisms are Co-opted to Produce Play? Model 1: Multiple, independent origins coopting some common neurobehavioral system (convergence), which with evolutionary transformation can become dissociated from its parent behavior system. Repeat this for multiple systems and you get many ‘play systems’, and when more than one play system becomes tertiary process play, involving high level executive brain functions, play from different systems can coalesce Each taps into the wanting and liking systems associated with each behavior system co-opted for play Object Play and Hunger: Object play cycles with hunger Object play associated with hunger in Asian small clawed otters Object play involves suing the behavior patterns associated with foraging and feeding All 36 Behavior Patterns used in stone play by long-tailed macaques are part of the foraging behavior system Mink No association between feeding and object play in mink Geleda baboons Only primate specialized for eating grass Hands are highly dexterous for plucking grass and eating grass Object play with stones reported in a captive population Stones do not resemble food items Such play is not associated with hunger The behavior patterns used include lifting and carrying, mouthing and cradling against the chest, which are not foraging typical actions Play as Multiple Behavior System that Borrows Behavior Patterns from Only One Other Behavior System Behavior System A – Play Behavior System A’ Behavior System B – Play Behavior System B’ New, Super-Play Behavior System? Thus, explaining object-social play mixture Model 2: Multiple, independent origins arising from a common mechanism (parallel evolution) as in the domestication syndrome). Therefore, even though originating independently, all forms of play share some common mechanisms Domestication events are independent, but uses the same mechanism that is latent in all animals Integrating the Whys – Developing a Comprehensive Framework Neural Crest Theory of Domestication Syndrome Proposes that during the domestication of animals, changes in neural crest development play a significant role in the emergence of certain traits commonly seen in domesticated species. 1. Neural Crest Cells: Arise during embryonic development and migrate throughout the body, contributing to the formation of various tissues and structures. These cells play a crucial role in the development of the nervous system. 2. Domestication: Involves a process where humans selectively breed animals for specific traits over generations. Leads to the emergence of characteristics not seen in their wild counterparts. 3. Neural Crest and Domestication Traits: The traits associated with domesticated animals, such as tameness, can be linked to alterations in neural crest development. 4. Genetic Changes: Domestication leads to genetic changes that affect the development and function of neural crest cells. These changes can affects physiology and behavior. 5. Evidence: Research on domesticated foxes. Provides understanding for how genetic changes during domestication can lead to the emergence of specific traits. The Evolution of Play We have already shown how play can diversify in a clade that contains play But the two models proposed in this lecture for how play emerges involves disparate lineages independently producing a new phenotype, one that can play. However, how this is achieved differs between the two models. Model 1: Convergent Evolution Where unrelated species independently evolve similar traits or characteristics in response to similar environmental pressures or ecological niches. The remarkable adaptability of living organisms and underscores the influence of environmental factors in shaping evolutionary outcomes. It also emphasizes that similar solutions can evolve independently in nature, highlighting the complex interplay between genetics, environment, and natural selection. Model 2: Parallel Evolution The independent development of similar traits or characteristics in closely related species that share a common ancestor. Occurs within a specific lineage or group of organisms. Showcases how closely related species can independently evolve similar adaptations in response to similar environmental challenges. It highlights the role of shared ancestry and genetic background in shaping evolutionary outcomes within specific groups of organisms. The Evolution of Eyes: Like play, eyes evolved sporadically across the animal kingdom All eyes, irrespective of what they look like, are all dependent on shared genes, particularly the master gene, Pax-6 Therefore, because eyes are built on traits shared by a common ancestor, the convergence is a case of parallel evolution. Back to the Evolution of Play Model 1: The similarities can be explained by the similar functional demands on play Model 2: The similarities can be explained by using common latent processes. Implications for the Ontogeny of Play Ontogeny of play also needs to be put in the context of this framework First, although we know a lot of bits and pieces of the mechanisms that regulate play and how those mechanisms develop, there are a few features that we know to be universal. Second, for cases of tertiary process play that have been established functions, we need to identify the age at which the play is adaptive, then determine how it emerges. Consider play fighting in rats – juvenile play matures after weaning and gains properties that facilitate the development of EF whereas adult typical pattern is not fully mature until after sexual maturity and gains properties suitable for testing and reinforcing social relationships.