Hunting on Land May Have Helped Spur Brain Evolution

The Okavango Delta’s patchy landscape is a good example of the “Goldilocks landscape” where the ability to plan results in a huge survival payoff. (Photo courtesy of Tim Copeland)

(CN) — New evidence in evolutionary science revealed Tuesday shows that land animals became smarter than their aquatic ancestors thanks to the complex landscapes they inhabited, allowing them to develop planning abilities that increased their survival rate.

In a study published Tuesday in the journal Nature Communications, researchers from Northwestern University discovered a likely explanation as to why land dwelling animals, including humans, have become so intelligent, and it’s all about the environment.

The open ocean is vast and empty, and therefore animals rely on habits and instinct for survival, whereas on land there exists elaborate topography. Bushes, trees, rocks, and crevices make easy hiding places for prey and camouflage opportunities for predators, which over time would allow them to evolve and develop planning strategies for survival.

Assuming natural selection favored individuals with these desired traits, we know evolution gave rise to animal populations with increased intelligence and survival skills. But researchers found through conducting computer simulations that the ability to plan for future outcomes did not give land dwellers the advantage in all landscapes.

They found that there is a “Goldilocks level of barriers” for predators, meaning their planning skills give them the upper hand when there are not too many or too few obstacles. For example, vast open landscapes provide no advantage, and neither do thick, dense forests.

“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?” asked lead author Malcolm MacIver from Northwestern University. “Our work shows that it’s not just about what’s in the head but also about what’s in the environment.”

The authors note that this discovery does not apply to aquatic animals like dolphins and whales, who are land mammals that have returned to the water over time.

MacIver has revealed through previous studies that when animals began moving onto land 385 million years ago, they developed the ability to see approximately 100 times farther than they could underwater. With that in mind, he hypothesized in this study that seeing that much farther would require an animal to use more “brain power” to hunt and survive on land than in open waters.

The simulations showed, however, that seeing farther and planning was not enough to increase chances of survival. They found instead that the best odds of success were achieved with exceptional vision and a landscape with both dense vegetation and open clearings.

“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.”

The process of this study consisted of MacIver and his colleagues developing simulations to further test his hypothesis. The tests involved a prey being hunted by a predator under two different conditions: the predator is habit based, acting out of habitual routine, or plan based, predicting different outcomes and choosing the best course of action.

Then, they tested these scenarios in a large, open world without barriers to represent the ocean, and a dense, obstacle ridden world for land.

“When defining complex cognition, we made a distinction between habit-based action and planning,” said MacIver. “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.”

The results showed that in the open aquatic and terrestrial landscapes, survival rates were low in prey regardless of habit-based action or plan based, as was true for dense and over complicated landscaped.

“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.”

The most ideal landscape was one interspersed with vegetation and open space, much like a savanna. The team saw that plan-based decision making showed the most success, which natural selection would have favored resulting in animals evolving with the brain power to consider future scenarios and enact the best one.

“With patchy landscapes, there is an interplay of transparent and opaque regions of space and long-range vision, which means that your movement can hide or reveal your presence to an adversary,” MacIver said. “Terra firma becomes a chess board. With every movement, you have a chance to unfurl a strategy.”

“Interestingly, 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 added.

This study is the latest installment in a series of studies by MacIver pertaining to the theory of land animals evolving to plan ahead. Moving forward, he and professor of neurobiology at Northwestern, Dan Dombeck, are conducting a follow up study using the results from these simulations to test with small animals in a robotic reconfigurable environment.

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