Risk taking behavior is a bit of a conundrum. By definition, it’s risky—some people win and some people lose. If these losing individuals are worse off as a result, you might expect natural selection to select against the trait, removing it from the population. But in reality, people take risks every day. How can this be?
First, let’s consider how natural selection acts on a population. Individuals within a population are all different; their DNA contains unique variation that contributes to their individual phenotypes. These differences can help someone survive or may contribute to an individual not having any offspring. For example, a bird born with uncharacteristically dull-colored feathers may not be able to find a mate. An individual who is resistant to a new disease may be able to have more offspring than those who don’t and therefore passes the advantage on.
So is risk taking a benefit or a hindrance? An interesting paper from 2010 looked specifically at risk taking to understand why and how it might persist in a population, offering a bit of clarity to this this apparent contradiction.
For their study, they compared two computer-simulated populations: one “risk-seeking” and one “risk-averse.” In the first model there was no benefit to risk taking overall. This means that in the population, taking a risk and succeeding was balanced by taking a risk any failing. Succeeding in this situation might be getting more food, mating more frequently, or acquiring a larger territory, balanced by going hungry, not mating, and losing territory. When they performed the simulation until one of the populations went extinct, the “risk-seeking” population lost.
But this outcome was completely switched in their second experiment. This time, they modeled a situation where the offspring of “risk-seeking” parents inherit a small fraction of the successes or failures. In this scenario, the “risk-seeking” population dominated. In the human population, this would be similar to parents passing on an inheritance as well as their acquired knowledge. Even when some individuals in the “risk-seeking” population failed, the trait was beneficial to the population overall. Maybe that’s why we humans continue to roll the dice.