Even fruit flies succumb to cultural dating pressures

Fruit flies might not sing songs, make art, or don traditional garments, but that doesn’t mean they don’t have culture. New evidence suggests female fruit flies (Drosophila melanogaster) can create unique dating customs based on the partners they see other female fruit flies select.

Cultural traditions—the traits and behaviors that are handed down across generations and spread through social learning—have been found in the grooming patterns of certain apes and the songs of some whales and birds. But scientists had little proof that smaller creatures such as insects could have culture.

So researchers set up a series of experiments in which one “observer” female fruit fly watched a “demonstrator” fly pick between two males that differed only in their artificial color—pink or green. When it was their turn to mate, observers chose the same color of mate more than 70% of the time, compared with random chance, researchers report today in Science.

The team also tested how reliably preferences were passed to the next generation by placing 12 observers in the center of a hexagonal container surrounded by six demonstrators who went exclusively for either pink or green males. In the next round of mating, the first observers to mate became the demonstrators. Over the course of 36 trials, the pink or green preference “trickled down” to the eighth generation of flies before they started to choose randomly again.

But when groups were bigger than 30 flies per generation, the team found—using computer simulations—that the inherited preference was much more likely to persist and snowball over thousands of generations.

The scientists want to use their results to probe both the genetics and brain circuitry behind the flies’ social learning; they also hope to test the phenomenon of cultural inheritance in wild insect populations, and see whether they can discover any hidden cultural traditions in species beyond large mammals and birds.