Phylogeny

The evolutionary history of animal play is complicated and it is currently impossible to point to a single origin or history of play.  Because it is so widespread across animals, it is likely that play has ancient roots, and has evolved independently many times and has been subsequently lost in many species.

Perhaps the biggest contributor to this specific field is Gordon M. Burghardt.  Burghardt studies what animals exhibit play, and from this work has described evolutionary hypotheses about this phenomena.  Importantly, he has described the conditions under which play appears to evolve, and suggests a specific process by which play evolves. His book, Animal Play: Testing the Limits (2005) is his primary contribution to literature on the evolution of play.  This page pulls information from several of his works, which can be found in REFERENCS.


Where animal play is found

Play is most prominently observed in endothermic animals and vertebrates, but recently play outside these categories has been discovered.  The classes that demonstrate play most predominantly include primates, carnivores, rodents, ungulates, elephants and cetaceans.  Below is a phylogeny tree created by Burghardt (2010) depicting the animal classes that demonstrate playing in at least 1 species.

Conditions that support play

Certain environmental factors tend to support playful behaviors more than others.  Burghardt’s surplus resource theory identifies several factors that appear to facilitate play.  Physical factors he cites include health, and physiology and diets that can support sustained physical activity.  Social factors that contribute to play include availability of play partners, social openness between individuals, and type of parental care.  Parental care allows juveniles to have more surplus time which they can then spend dedicated to playing.  Burghardt suggests that animal play tends to evolve in animals whose environment meet the above needs.  

How Play Evolves

Burghardt has suggested a process by which play may evolve using three different stages.  Primary process play represents the proximate causes of play before it has been selected for.  In this stage, playing behaviors arise somewhat sporadically from factors such as low behavioral thresholds, boredom, excess energy and maturation.  Secondary process play represents play after some initial selection.  Here play has evolved some purpose after its initial occurrence, but its role is not major, and instead represents maintenance or refinement of behavior.  Tertiary process play is play that has evolved some major function.  These processes are suggested to occur sequentially both phylogenetically and ontogenetically, however all 3 can be observed simultaneously in the same species.  In this case, animals still produce play due to the factors that initially caused it to occur in addition to its subsequent evolved functions.  Below is a figure from Burghardt (2010) but more information can be found in his book (2005).

 

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