writer and photographer PETER GRANT

Walking and thinking go hand in hand – as Rebecca Solnit put it, when you walk you move at the speed of thought. My regular walks in The Patch, the large area of bush behind our place, bear this out. My mind, transported by my legs, wanders wherever it will.

But today, of all the things I might think on as I walk, I am thinking about the act of walking itself. Birds fly, lizards scamper, butterflies flutter and dragonflies hover, so why do we humans get around on two legs? In the broader animal kingdom, creatures that move primarily on two legs are quite rare. As I walk, I self-consciously consider how it works. I conclude that two-legged walking is essentially the constant prevention of toppling by the placing of one foot in front of the other. This sounds simple, but in watching one of our grandchildren master bipedal walking, I had to admire the skill and will it took to prevent his pumpkin-weighted, top-heavy head from bringing him smashing to earth.

Only familiarity and continual practice can disguise the wonder that is walking.

There’s another very particular reason I don’t take for granted the wonder of walking. I was born the year Jonas Salk developed the first poliomyelitis vaccine. The vaccine went on to save hundreds of thousands of lives and end the crippling effects of the disease. Before the vaccine’s dissemination, outbreak years in Australia would see thousands of people infected. Of those, the disease typically killed more than a hundred, and left thousands unable to walk. My great uncle Gwesyn was one of them.

For many years his presence, metaphorically more than physically, was a powerful and fearful one for me. On Sundays our family would sometimes visit Gwesyn’s sisters, my fraternal grandmother and my great aunt. But we would seldom see any more hint of great uncle Gwesyn than a wheelchair or discarded walking cane in the darkened hallway. On rare occasions we would hear his voice from the end room. It added a frisson of excitement to the atmosphere of drawn curtains, whispered conversations, doilies and polite cups of tea at grandma’s. For some reason, probably a misguided desire to “protect” us from his suffering, it was many years before we properly met Uncle Gwesyn. Thereafter he became a dear member of our wider family, but his story remained a powerful personal reminder that walking is a gift to be cherished.

Back in The Patch, as I’m thinking about this precious gift of bipedal ambulation, I come face to face with a pair of Bennett's wallabies. They are particularly healthy, if their fine coats and broad tail bases are anything to go by. Unlike humans, wallabies store fat in their tails rather than around their bellies. In the event of lean times, they can tap into that store of energy.

We see this particular pair regularly, so they’re not initially startled by our presence. Instead, they watch us coming, and simply turn their heads to follow our progress. The larger of the two has a reddy-brown tinge to his neck, the origin of their other common name: red-necked wallaby. That red contrasts with the pale grey of his belly and his near-black muzzle, almost a perfect match for the colours of the stringybark tree beneath which he stands.

Both wallabies are a little wary, ears up like radars, and as we move closer, they decide that’s enough. Each places front paws briefly on the ground before leaping off with surprising speed. We watch, admiring their agility, and their ability to avoid trees and shrubs as they bound away.

Only then does it strike me: these wallabies are also bipeds. Not even our near relatives, the chimpanzees, can claim as much. Chimps are essentially quadrupedal, getting around by knuckle-walking on all fours. In evolutionary terms bipedalism conferred an adaptive advantage on hominids, especially when food resources were scarce. Bipeds would have expended less energy moving from one food source to another. And standing upright would have added to that advantage by allowing them to spot food and water from further away.

The need for energy efficient movement is obvious in Australia, with its often hot, dry climate, and dispersed food resources. And that leads me back to those other bipeds I’ve just been admiring. The bipedal bounding gait of macropods is thought to be to an adaptation that allows greater energy efficiency over long distances. Their large, muscle-bound back legs have been shown to use less effort per mile than standard-model herbivorous mammals such as deer and cattle.

Essentially, kangaroos and wallabies are the bowser wowsers of the animal world, showing us how efficient bipedalism can be. Of course, as with the different ways in which we store fat, human bipedal movement – walking or running – is very different from the bounding gait of macropods. Not since pogo sticks were a fad in my childhood have I tried getting around using a bounding gait. The bruises I had to show for my lack of skill on a pogo stick, give me a renewed admiration for our beautiful bush bounders. And perhaps just a little tail envy.

Peter Grant lives in the foothills of kunanyi/Mt Wellington with his wife. He worked with the Tasmania Parks and Wildlife Service for 24 years as manager of interpretation and education. His passion for the natural world led him to write Habitat Garden (ABC Books) and found the Wildcare Tasmania Nature Writing Prize. More of his writing can be seen at naturescribe.com.