This 2021 review subject was individual differences:
“We will focus on recent findings that try to shed light on the emergence of individuality, with a particular interest in Drosophila melanogaster.
- (A) Cumulative and relative contribution of different sources of interindividual variability from early development stages to adult life experience. Individuality emerges from the combination of genetic factors, environmental factors, and stochastic factors.
- (B) Variance distribution for a given phenotypic trait evoking variability among individuals within a population (Is what’s true for a population what’s true for an individual?).
- (C) Variance distribution of phenotypic handedness is inherited to next generations within a population (Changing an individual’s future behavior even before they’re born).
Another possible source of potential behavioral variability might come from the interaction of individuals with environmental microbes, from Wolbachia infections to changes in the gut microbiome. In this particular case, no genetic variation or neural circuit alteration would be responsible for the change in behavior.
Finally, from an evolutionary point of view, individuality might play an essential role in providing an adaptive advantage. For example, we have described that animals might use diversified bet-hedging as a mechanism to produce high levels of variation within a population to ensure that at least some individuals will be well-adapted when facing unpredictable environments.”
https://www.frontiersin.org/articles/10.3389/fphys.2021.719038/full “Behavior Individuality: A Focus on Drosophila melanogaster”
Other papers on this subject include: