"You are unique, just like everyone else." This age-old adage captures a real biological phenomenon: all animals, including humans, exhibit distinctive behavioral patterns. This individuality ultimately shapes what we consider intelligence, influencing how we navigate and succeed in our environments. It raises the question: are we the way we are because of our genes, or because of our experiences? Science shows the answer is both: genes and environment interact to produce variation. Yet recent work suggests a third component: even genetically identical animals in identical environments display strong behavioral individuality from the very first day of life. That early variation continues to diverge and predicts behavior throughout the lifetime. To fully understand what makes us unique, a developmental perspective is required.

A project led by Kate Laskowski at UC Davis challenges the "nature vs. nurture" dichotomy by investigating developmental stochasticity as a third driver of behavioral variation. The team studies the Amazon molly, a clonal fish where all offspring from a single mother are genetically identical. This system allows a true replicate individual approach (i.e., twin study) to test how experience influences the development of individuality. With a custom-built, high-resolution automated tracking system monitoring individuals continuously from birth, the team can measure environmental influences and behaviors in detail.

The project has two aims. First, to test how a mother's experience of environmental uncertainty — specifically predation risk, simulated with chemical cues — shapes individuality in her offspring. The hypothesis is that mothers exposed to risky, unpredictable environments will produce young with greater behavioral variation as a bet-hedging strategy. Second, to identify the molecular mechanisms behind these effects by examining how maternal risk exposure alters gene expression, DNA methylation, and brain development in offspring.

Ultimately, the project seeks to shift understanding of behavioral development from a deterministic to a probabilistic model, reframing variation as a vital source of resilience and intelligence in unpredictable environments.

Photo: ©David-Bierbach