Various scientists have tried to settle the nature vs. nurture debate by tinkering with fruit flies. For instance, Science Daily describes a 2007 study in which University of Chicago researchers altered the insects’ sexual orientation by genetically altering and drugging them. While that sounds vaguely illegal, it proved to be a fruitful way to make flies bisexual or homosexual. Similarly, in 2009, scientists at the University of Toronto turned fruit flies into “lusty Lotharios” by manipulating pheromone production. Preventing the creation of certain pheremones “triggered a sexual tsunami” as unaltered male fruit flies tried to get it on with pheromone-free males and pheromone-free female flies of a different species. Admittedly, this all sounds less like hardwiring than rewiring hardness, but it illustrates that a trait like sexual orientation has a strong biological component.

In 2020, researchers and Germany, Belgium, and France have made the claim that “random” noise might decide individual differences in fruit flies. Per Phys.org, previous research demonstrated that random noise can shape the brain structure of humans and other animals in the womb. So the researchers induced fruit flies to walk toward an object, then dissected the insects to analyze their brains. Flies that walked in straight lines had symmetric brain wiring while those meandered had wiring consistent with the effects of random noise. Admittedly, it isn’t clear how random noise doesn’t count as part of one’s environment or how walking in a straight line reflects a fly’s personality or other behavioral tendencies. So perhaps their interpretation is also random noise.