Playfulness and creativity

Why don’t we see more invertebrates playing? Play may have arisen in vertebrate lineages as a by-product of traits associated with the complex behaviours and cognitive abilities, in turn associated with increased brain size. Although we know that invertebrates are far from the mindless machines they were once considered to be, it might be that the neural architecture available to add new levels of control required for play is lacking, or the local solutions employed by invertebrates don’t benefit from the adaptive advantages conveyed by play. Or perhaps it is simply that we are overlooking countless examples of play in invertebrates. For example, sex play may be more common in arthropods than we think: there are over 100 species of insect known to exhibit same sex courtship and/or copulation, often with no apparent immediate function. Moreover, a few years ago a study showing that sexually deprived male Drosophila melanogaster increased their ethanol intake led to headlines such as “Sexually deprived male fruit flies get drunk to ease the pain of rejection”. This study highlighted that invertebrates can indulge in behaviours that are not useful in themselves, but which act on neural reward centres to attain something akin to pleasure, so perhaps the concept of invertebrate fun isn’t so farfetched after all.