Fruit flies enjoy ‘culture’ and ‘tradition’

It may be hard to believe, but those tiny specks swarming your overripe bananas have their own aptitude for culture and tradition, scientists have found. 

Fruit flies (Drosophila melanogaster) have culture and local traditions that get passed on through social learning, according to a study that looks at how females of the species learn to prefer certain male “looks”, or phenotypes, based on what they see other female flies choose.

In a lab experiment, researchers, led by Etienne Danchin of the Université de Toulouse, France, allowed female fruit flies to observe which type of males other females chose for mating. They were then given the opportunity to either replicate that behaviour or choose a different phenotype. 

Male fruit flies used in the tests were green or pink. Some were wild-type, while others had unusual curly-wings, or white eyes. 

Danchin and colleagues saw that the observer flies copied the “local” customs.{%recommended 7482%}

“Informed females mated preferentially with new males of the colour they saw being chosen during the demonstration,” they write in the journal Science. 

The researchers note that “culture used to be considered to be limited to humans”, but that scientists now understand something “akin to traditions” exists in some other mammal species, and birds. 

“The typical criterion of culture is generally that transferred traits must be socially acquired and spread to others repeatedly,” they write. This appears to be the first time flies have made the grade. 

Danchin’s team tested for culture using five criteria. They looked for evidence of strong social learning that occurred across age classes. The learning had to be memorised and repeated, trait-based, and conformist. Using various experiment designs, all based around female flies choosing particular male phenotypes, the researchers found that all the criteria were met. 

“Our lab experiments thus can be seen as a proof of concept in the lab that D. melanogaster has all the cognitive capacities and dispositions to transmit female mating preferences culturally across generations in ways that can elicit potentially long-lasting traditions of preferring an arbitrary male phenotype,” Danchin’s group writes. 

“This suggests that the taxonomical range of culture may be much broader than ever before envisioned.”

The researchers suggest their findings shed light on how culture affects evolution, since mates are being chosen due to cultural influence or tradition. They note that the fact that newcomers have to quickly adapt is evidence of peer pressure.