Scared fitless: the evolution of fearlessness

Understanding the evolution of fearlessness could aid conservation efforts

While fear may play a strong role in animal extinction, the lack of fear can be equally problematic, as shown by dodos, Falkland Island foxes, and Steller’s sea cows, all driven to extinction because they failed to fear humans.

In a second study, Kyle Elliott, a professor in McGill’s Department of Natural Resources and his colleagues at Guelph University looked at the evolution of fearlessness in fruit flies. Fearlessness plays an important role in conservation because fearless animals are particularly vulnerable to predators. 

The researchers were interested in looking at how adult and larval fruit flies responded once a predator (either alive or dead) was introduced into their environment (the flies were separated from the predators by a small piece of cotton).

“Fruit flies are very useful for looking at evolution because their breeding seasons are so short – as little as 3 days – that it means that you can reproduce some of the processes of evolution relatively rapidly,” says Ryan Norris, an associate professor at the University of Guelph and a coauthor on the study. “This means that we were able to look at how flies evolved with and without predators for hundreds of generations very quickly.”

Thousands of generations of fearfulness

Adult fruit flies, for whom there was no food cost to being shy and fearful since they had been raised with sufficient food, were fearful in the presence of the predator and continued to show fearfulness for up to 1000 generations after exposure to the predator. In contrast, juvenile fruit flies, which had to compete for food, quickly evolved to become fearless, despite the presence of a predator, since the bolder individuals ate more, grew faster and became stronger adults.

“Our study is one of the first to demonstrate experimentally that competition for food or mates can lead to the evolution of an emotion, fearlessness.” says Gustavo Betini, a coauthor at the University of Guelph. “Understanding how fearlessness evolves could help in the conservation of island species and in formulating responses to invasive predators.”

Together, the two studies show why both fear and fearlessness can contribute to animal extinction.

To read “Fear creates an Allee effect: experimental evidence from seasonal populations” by Kyle Elliott et al in the Proceedings of the Royal Society:

To read “Scared fitless: context-dependent of fear to loss of predators over evolutionary time in Drosophila melanogaster” by Kyle Elliott et al in FACETS:

The research was funded by: NSERC.


Kyle Elliott, Dept. of Natural Resource Sciences, McGill University
kyle.elliott [at]

Katherine Gombay, Media Relations Office, McGill University
katherine.gombay [at]">​katherine.gombay [at]

Ryan Norris, Dept. of Integrative Biology, University of Guelph
rnorris [at]

Gustavo Betini, Dept. of Integrative Biology, University of Guelph
betinig [at]

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