How the geometry of ancient habitats may have influenced human brain evolution
Hunting in savanna-like landscapes may have helped give rise to planning circuits in the brain. Rife with obstacles and occlusions, terrestrial environments gave prey spaces to hide and predators cover for sneak attacks.
There's a pivotal scene in the 2012 film The Hobbit: An Unexpected Journey when Gandalf, Bilbo Baggins, and a company of dwarves are chased by orcs through a classic New Zealand landscape. For Northwestern University neuroscientist and engineer Malcolm MacIver, the scene is an excellent example of the kind of patchy landscape-dotted with trees, bushes, boxers, and rolling knolls-that may have shaped the evolution of higher intelligence in humans, compared to their aquatic ancestors. Specifically, it falls within a "Goldilocks zone"-not too sparse, and not too dense-that favors strategic thinking and planning ahead, leading to the development of "planning" circuitry in the human brain, according to MacIver's most recent paper, published in Nature Communications.
This latest paper builds on earlier research. Back in 2017, MacIver and several colleagues published a paper advancing an unusual hypothesis: those ancient creatures who first crawled out of the water onto land may have done so because they figured out there was an "informational benefit" from seeing through air, as opposed to water. Eyes can see much farther in air, and that increased visual range could lead them to food sources near the shore. MacIver and his primary co-author, paleontologist Lars Schmitz of the Claremont Colleges, argued that this in turn drove the evolutionary selection of rudimentary limbs, enabling the first animals to move from the water onto land.
That hypothesis grew out of his research on the black ghost knifefish of South America, which is a nocturnal hunter that generates electrical currents in the water to sense its environment. After building a robotic version of the knifefish, with its own electrosensory system, he found that the volume of space in which it could detect prey (in this case, water fleas) was about the same as for a fish that relies on vision to hunt water fleas. The critical factor turned out to be that water absorbs and scatters light, limiting how far that light can travel: typically 10 centimeters to 2 meters, compared to the 25 to 100 kilometers light can travel in air.
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