Mixed habitat and complex topography, like the combination of open spaces and patches of vegetation found in savannas, forced predators and prey to develop advanced planning -- strategies that required bigger, more powerful brains. Photo by Tim Copeland
June 16 (UPI) -- Computer models suggest the unique challenge of hunting on savanna-like landscapes accelerated brain evolution among terrestrial species.
The simulations -- detailed Tuesday in the journal Nature Communications -- offer an explanation for why animals on land evolved bigger, more powerful brains than their aquatic ancestors.
"All animals -- on land or in water -- had the same amount of time to evolve, so why do land animals have most of the smarts?" lead study author Malcolm MacIver, professor of biomedical engineering at Northwestern University, said in a news release. "Our work shows that it's not just about what's in the head but also about what's in the environment."
Dolphins and whales are quite intelligent, and they live in the ocean, a seeming contradiction, but like many of the smartest sea creatures, they evolved on land before returning to the sea relatively recently on the evolutionary timeline.
MacIver hypothesized that hunting on land forced terrestrial animals to develop advanced planning strategies, instead of relying on simple habit -- see minnow, chase minnow.
In an earlier study, MacIver used computer models to show that animals that transitioned from the sea to land quickly evolved more powerful eyesight. Their new and improved eyesight required greater brainpower. However, the supercomputer models developed by MacIver showed improved eyesight was necessary but not sufficient, on its own, for advanced planning.
In the followup simulations, MacIver's models determined animals with long-distance vision evolved advanced planning strategies when placed in landscapes featuring a mix of open spaces and more densely vegetated areas -- like grassland peppered with patches of forest.
"We speculated that moving onto land poured jet fuel on the evolution of the brain as it may have advantaged the hardest cognitive operation there is: Envisioning the future," MacIver said. "It could explain why we can go out for seafood, but seafood can't go out for us."
MacIver and his colleagues built a new model to determine how prey would evolve their behavior in an open water-like world featuring predators hunting by habit and a savanna-like world with predators using advanced planning.
"When defining complex cognition, we made a distinction between habit-based action and planning," MacIver said. "The important thing about habit is that it is inflexible and outcome independent. That's why you keep entering your old password for a while after changing it. In planning, you have to imagine different futures and choose the best potential outcome."
In both worlds, prey didn't fare well, regardless of whether they used habit-based behaviors or relied on planning. The model revealed similarly low survival rates for prey in crowded environs, such as coral reefs and jungle.
"In those simple open or highly packed environments, there is no benefit to planning," MacIver said. "In the open aquatic environments, you just need to run in the opposite direction and hope for the best. While in the highly packed environments, there are only a few paths to take, and you are not able to strategize because you can't see far. In these environments, we found that planning does not improve your chances of survival."
However, when the model used a savanna-like landscape, featuring a mix of open space and patches of vegetation or complex topography, prey using planning instead of habit-based behaviors benefited from a large increase in survival rates.
The findings suggest the challenge of finding prey and avoiding predation in variable landscapes like savannas fueled the development of bigger, more powerful brains among land animals.
MacIver's theory for how terrestrial animals evolved greater intelligence mirrors the explanation for the accelerated brain development of early humans.
"When we split off from life in the trees with chimpanzees nearly seven million years ago and quickly quadrupled in brain size, paleoecology studies point to our having invaded patchy landscapes, similar to those our study highlights, as giving the biggest payoff for strategic thinking," MacIver said.