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WHEN a sea squirt settles on a home, it never gives another thought to going out. In youth, squirts are constantly on the prowl, swimming in rock pools and hunting for prey. But once an adult finds suitable real estate, it permanently attaches to the stone, consumes its own spinal cord and brain, and spends its remaining days capturing whatever nutrients float by.

According to neuroscientist Shane O鈥橫ara, this life cycle is perfectly sensible. 鈥淏rains have evolved for movement,鈥� he writes in In Praise of Walking. 鈥淚f you鈥檙e going to be stuck鈥� with your food all around you, then why do you need a costly brain?鈥�

O鈥橫ara uses the sea squirt and similar creatures to evoke the essential connection between walking and cognitive activity in humans. From his perspective, mobility is one of the defining qualities of animals including Homo sapiens, and the sessile lifestyle of the modern couch potato is dangerously unnatural.

The benefits of taking to our feet could easily fill a book, and O鈥橫ara does devote whole chapters to them. The physical benefits are well known: cardiac health, muscle development and improved digestion. The cognitive gains are less well known but at least as dramatic.

Take the Stroop test, a standard measure of cognitive control in which the word for a colour is written in a different hue (鈥渞ed鈥� written in green ink, say) and the subject must name the ink colour as fast as possible. Mismatched stimuli tend to slow people down, especially when asked to perform other tasks simultaneously.

鈥淭he way in which we walk is adapted to endurance, which may make us the best walkers of all species鈥�

But as O鈥橫ara explains, a 2017 study by David Rosenbaum, a psychologist at Tel Aviv University in Israel, showed that standing up significantly improves performance. 鈥淚t is as if the mere act of standing mobilises cognitive and neural resources that would otherwise remain quiescent,鈥� writes O鈥橫ara. Other recent studies show that blood flow to the brain increases with walking, and this alters the brain state as it calls on greater cognitive resources, 鈥渃onstituting a call to action as well as鈥� to cognition鈥�.

In the interest of praising walking as roundly as possible, O鈥橫ara seeks out the big picture as he considers, for example, the mechanics of walking 鈥� a rhythmic action underlying motion and balance. This has a genetic basis dating back at least 420 million years, revealing an evolutionary relationship between walking and swimming. At the opposite end of the timeline, he considers the walkability of cities and proposes improvements to urban planning.

O鈥橫ara is especially keen to show how walking made us what we are today. The morphological changes that allowed us to stand upright 鈥� including alterations to the skull, pelvis and feet 鈥� freed our hands for foraging and carrying babies. But the biggest impact was on migration. The way we walk is adapted to endurance, making us 鈥減ossibly the best walkers of all species鈥�, he writes. By radiating out of Africa on foot, we eventually colonised most continents and habitats.

One legacy of this activity is the knack for moving in groups, whether as soldiers on the march or as an army of protest. Another is our remarkable efficiency as walkers, and O鈥橫ara cites a recent study that measured walking efficiency using exoskeletons. It showed that humans intuitively expend as little energy as possible.

Unfortunately, the effect of covering so much territory, often in passing, doesn鈥檛 help the book overall, as O鈥橫ara has a tendency to ramble. That and a sometimes pedantic writing style aside, In Praise of Walking is both informative and persuasive enough to rouse the most ardent couch potato 鈥� perhaps saving humanity before our lifestyle consumes our brains completely.