Animals Compare the Present with the Past: Evolutionary Advantage Seen in Different Species

Humans can compare the present with the past. We examine our lives and judge how previous conditions may have been better or worse than present ones. Now, though, new research reveals that such comparisons give individuals an evolutionary advantage--including among animals.

In order to understand how animals and humans should behave when they are uncertain about a pattern of environmental change, the researchers created a mathematical model. Although standard theory dictates that the best response to current circumstances should be unaffected by what has happened in the past, the new model seemed to demonstrate the opposite.

So what did the model predict? It showed that when animals are used to rich conditions and then conditions suddenly worsen, they actually work less hard than animals exposed to poor conditions all along. This so called 'contrast effect' has also been reported in bees, starlings and a variety of mammals, including newborn children.

"The effects in our model are driven by uncertainty," said Tim Fawcett, a research fellow in Bristol's School of Biological Sciences, in a news release. "In changing environments, conditions experienced in the past can be a valuable indicator of how things will be in the future. An animal that is used to rich conditions thinks that the world is generally a good place. So when conditions suddenly turn bad, it interprets this as a temporary 'blip' and hunkers down, expecting that rich conditions will return soon."

So what implications does this model hold for the future? It shows that unpredictable environmental fluctuations could have a huge impact on the process of evolution--and also on the survival of species.

"Rapid changes favor individuals that are responsive and able to adjust their behavior in the light of past experience," said Fawcett in a news release. "The natural world is a dynamic and unpredictable place, but evolutionary models often neglect this. Our work suggests that models of more complex environments are important for understanding behavior."

The findings are published in the journal Science.