“Place and a mind may interpenetrate till the nature of both is altered,” the Scottish mountaineer and poet Nan Shepherd wrote in her lyrical love letter to her native Highlands, echoing an ancient intuition about how our formative physical landscapes shape our landscapes of thought and feeling. The word “genius” in the modern sense, after all, originates in the Latin phrase genius loci — “the spirit of a place.”

I find myself thinking about Shepherd as I return to the Bulgarian mountains of my own childhood, trekking the same paths with my mother that I once trudged with tiny feet beside her, astonished at the flood of long-ago feelings rushing in with each step, astonished too at how effortlessly I navigate these routes I have not walked in decades.

The psychological, neurocognitive, and geophysical underpinnings of these astonishments are what M.R. O’Connor explores in Wayfinding: The Science and Mystery of How Humans Navigate the World (public library) — a layered inquiry into the science and cultural poetics of how we orient in space and selfhood, illuminating the stunning interpenetration of the two.

In a passage evocative of Rebecca Solnit’s memorable observation that “never to get lost is not to live,” O’Connor takes the telescopic perspective of evolutionary time to consider the cognitive handicap beneath this existential gift:

Life on earth has created millions of Ulyssean species undertaking epic journeys at scales both large and small. Getting lost is a uniquely human problem. Many animals are incredible navigators, capable of undertaking journeys that far eclipse our individual abilities. The greatest migration on earth belongs to the Arctic tern, a four-ounce argonaut that travels each year from Greenland to Antarctica and back again, a distance of some forty-four thousand miles. Flying with the wind, the tern’s return itinerary is a globe-trotter’s fantasy, circumnavigating Africa and South America.

[…]

One of the devices that an animal needs to navigate is a “clock” — an internal mechanism for measuring or keeping time. The daily mass migration of zooplankton in the world’s oceans requires them to know when dawn and dusk are approaching. It would seem this is a simple response to light stimuli, but deep-sea zooplankton, which live at depths below where light penetrates, also migrate in accordance with the length of day at different latitudes. Even slightly more complex migrations can demand multiple clocks.

Perhaps the most astonishing internal clock belongs to the bioluminescent Bermuda fireworm, which swarms the tropical waters precisely fifty-seven minutes after sunset on each third evening after the full Moon in the summer. Such a feat suggests that this tiny marine organism, with a fraction of a fraction of the cognitive capacity of a human, is internally equipped with three different timekeeping devises: a regular twenty-four-hour diurnal clock, a lunar clock with a 27.3-day cycle, and an interval timer to tick out the exact minutes past sunset.

O’Connor marvels at the staggering evolutionary array of timekeeping devices that allows migratory species to keep partaking of the dance of life:

Animals that complete annual migrations or multiyear migrations have to possess a yearly clock, one that is finely attuned to the lengths of days and nights and their changes across each season. In all, evolution seems to have produced annual clocks, lunar clocks, tidal clocks, circadian clocks, and, perhaps for those that migrate under cover of darkness, a sidereal clock — which measures the time it takes a star to appear to travel around the earth.

Besides their intricate internal timekeeping mechanisms, many nonhuman animals are endowed with equally intricate space-mapping mechanisms. Each migration season, humpback whales travel more than ten thousand miles far from land to return to the precise place where they were born. There are bird species — European pied flycatchers, blackcaps, and indigo buntings among them — that appear to orient by the pole star in their nocturnal flight; there are insect species — ants and bees among them — that perform triumphs of trigonometry with their light-sensitive photoreceptors, calculating spatial distances by polarized light to find the most direct route home after a winding pathway of foraging. With their mere milligram-brains of one million neurons — a grain of sand to the Mont Blanc of our eighty-six billion — and 20/2000 vision that renders them blind by human standards, honeybees make hundreds of foraging trips per day, meandering many miles from home, then compute the “beeline” back. African ball-rolling dung beetles, Namibian desert spiders, and southern cricket frogs use the stars of the Milky Way as their compass, just like some of the most courageous members of our own species once used the constellations to find their way to freedom from the moral cowardice of tyranny: To ensure they were moving northward, migrants on the Underground Railroad were instructed to keep the river on one side and “follow The Drinking Gourd” — an African name for Ursa Major, or The Big Dipper.

Like all reality-radicalizing discoveries that defy the limiting creaturely intuitions we call common sense, the notion that animals might use magnetism for navigation was long derided as something more akin to spiritualism than to science. Humphry Davy — the greatest chemist of the Golden Age of chemistry, charismatic pioneer of the scientific lecture as popular entertainment — was keenly interested in the mystery of animal magnetism. A century after him, Nikola Tesla — a dazzling mind epochs ahead of his time in myriad ways, whose legacy shapes so much of our daily lives and whose name is now the measuring unit of magnetic fields — stood a chance of cracking the mystery, given with his twin passions for pigeons and magnetism, but the opprobrium of the scientific establishment was too impenetrable and the technology was not yet there. It wasn’t until 1958 that a young German graduate student — Wolfgang Wiltschko — was tasked with disproving animal magnetic navigation once and for all. Instead, he ended up proving it: In the then-dubious experiment he was asked to replicate, the birds he let loose in a space with no light source could, just like in the original experiment performed by a fellow student, still orient effortlessly.

O’Connor writes:

The notion that animals have a bio-compass that can “read” the earth’s geomagnetic field has now emerged as the most promising explanation of animal navigation. In addition to those marathon migratory species, nearly every animal that has been tested thus far demonstrates a capacity to orient to the geomagnetic field. Carp floating in tubs at fish markets in Prague spontaneously align themselves in a north-south axis. So do newts at rest, and dogs when they crouch to relieve themselves. Horses, cattle, and deer orient their bodies north-south while grazing, but not if they are under power lines, which disrupt the magnetic field. Red foxes almost always pounce on mice from the northeast. These organisms must all have some kind of organelle that functions as a magneto-receptor, the same way an ear receives sound and an eye receives space.

We human animals navigate the world not only by orienting in space, but by orienting in time. Mental time travel — the ability to rememeber and reflect, to imagine and plan for the future — is what made us human. It is also the pillar of our personal identity — the narrative string that links our childhood selves to our present selves to make us, across a lifetime of physical and psychological changes, one person.

That string is known as autonoeic consciousness, from the Greek noéō: “I perceive,” “I fathom” — our capacity for mental self-representation as entities in time that can reflect on our own lives as continuous and coherent phenomena of being. In the blink of evolutionary time since the dawn of neuroscience in the 1930s, one area of the brain has emerged as the crucible of both our autoneoic consciousness and our spatial navigation: the hippocampus. O’Connor writes:

The hippocampus has sometimes been described as the human GPS, but this metaphor is reductive compared to what this remarkable, plastic part of our minds accomplishes. While a GPS identifies fixed positions or coordinates in space that never change, neuroscientists think what the hippocampus does is unique to us as individuals — it builds representations of places based on our point of view, experiences, memories, goals, and desires. It provides the infrastructure for our selfhood.

Because a self is a pattern of experiences, memories, and impressions, constellated according to an organizing principle, and because sleep is when the hippocampus consolidates memories to draw from them those organizing patterns, sleep is essential to our sense of self. O’Connor quotes MIT neuroscientist Matt Wilson:

During sleep you try to make sense of things you already learned… You go into a vast database of experience and try to figure out new connections and then build a model to explain new experiences. Wisdom is the rules, based on experience, that allows us to make good decisions in novel situations in the future.

The hippocampus is a hard-won glory of evolution, but it is not singular to us — rudiments of it and variations on it are found in some of our fellow animals across the rungs of neural complexity:

Even birds, which last shared an ancestor with humans 250 million years ago, as well as amphibians, lungfish, and reptiles, have what is called a medial pallium. Similar to the mammalian hippocampal formation in vertebrates, the medial pallium is also involved in spatial tasks in these species, raising the possibility that certain properties of spatial cognition were conserved as organisms diversified and split, while other properties adapted to particular ecologies or selective forces. But despite the profound evolutionary commonalities between humans and other vertebrates and the way the hippocampus relates to cognitive functions of memory and navigation, the question remains: why did we make such a leap in terms of hippocampi’s size and role in our lives? Or as psychologist Daniel Casasanto puts it, “How did foragers become physicists in the eye blink of evolutionary time?”

Part of the answer might lie in the remarkable plasticity of the hippocampus. After the now-iconic 2000 study of the brains of London taxi drivers — which found that their elaborate qualification exam, requiring the memorization of thousands of city landmarks and 25,000 streets, resulted in significant increase in synapses and gray matter in the hippocampus — scientists have been studying what we can do to protect and even bolster our primary instrument for navigating space and selfhood.

O’Connor points to the work of McGill University neuroscientist Véronique Bohbot, who has devised a hippocampal health regimen of recollection and navigation exercises of incrementally increasing difficulty that deliver marked structural growth of gray matter. VeboLife — the neurocognitive fitness training program she has devised — teaches people to navigate the familiar environment in deliberately novel ways, challenging trainees to reconfigure their default routes by taking new paths that require them to attend to new details and make new mental maps in the process.

Optimal hippocampal health appears to be — like the optimal experience of life itself — a matter of paying active and mindful attention, interrupting the “intentional, unapologetic discriminator” our brain has evolved to be, savoring the specifics of each unrepeatable moment.

With an eye to how our hippocampal acuity determines the quality of our lives, O’Connor wonders:

Maybe wayfinding is an activity that confronts us with the marvelous fact of being in the world, requiring us to look up and take notice, to cognitively and emotionally interact with our surroundings whether we are in the wilderness or a city, even calling us to renew our species’ love affair with freedom, exploration, and place.

And yet as much as we throb with wanderlust, we are animated by an intense connection to the landscapes and topographies of our formative years. An emotion known as topophilia, which I experienced while revisiting those mountain trails of my childhood, furnishes this affective-spatial memory that renders childhood as much a time as a place.

O’Connor writes:

Often the places we grow up in have outsized influence on us. They influence how we perceive and conceptualize the world, give us metaphors to live by, and shape the purpose that drives us — they are our source of subjectivity as well as a commonality by which we can relate to and identify with others. Maybe it’s because of the vividness of their sensory impressions, their genius for establishing deep relationships to their early environments, that children have a strong capacity for the human emotion called topophilia.

[…]

Across cultures, navigation is influenced by particular environmental conditions — snow, sand, water, wind — and topographies — mountain, valley, river, ocean, and desert. But in all of them, it is also a means by which individuals develop a sense of attachment and feeling for places. Navigating becomes a way of knowing, familiarity, and fondness. It is how you can fall in love with a mountain or a forest. Wayfinding is how we accumulate treasure maps of exquisite memories.

In the remainder of the thoroughly fascinating Wayfinding, O’Connor maps the most thrilling shorelines of our evolving territories of understanding: astounding findings indicating that people from migratory populations have measurably longer alleles of the dopamine receptor gene associated with exploratory behavior than people from sedentary communities; ancient feats of navigation passed down the generations in native cultures to challenge the Western social theory of culture; music as a metaphor for the relationship between organisms and their environment. For a lyrical counterpart, complement it with Rebecca Solnit’s Field Guide to Getting Lost.