When I go hiking I will invariably think about optimization. Once you see it, you can’t unsee it.
On most hikes I’ve been on, I see paths with trail forks, uphills and downhills, steep inclines and shallow grades, peaks, valleys, saddle points; rivers, fences, maps; signs with directions, signs with distances, and signs with warnings. Each of these has their own parallel or analogy to optimization algorithms and techniques. Some of those just mentioned are designed by people, but many are natural phenomena that have existed millions of years before me and will continue to exist far after I’m gone.
Nature itself is one of the best designers out there and optimization may be its best design tool. Some might even argue it is the only design tool.
Although I use the word optimization here, others might suggest the terms survival of the fittest, adaptive advantage, or natural selection as more descriptive phrases of the principle I’m discussing. However, I prefer the more general “optimization” because there are observations that are not the results of biological evolution but still expressions of optimization from a different point of view. You’ll hopefully see what I mean very shortly.
So, let’s go on a little hike together and point out some of these manifestations of optimization along the trail.
The hiking path below our feet is the first instance of optimization in action. The path is often well-defined and well-worn without much vegetation, especially if our hiking path is in a popular area and used by hikers all year round. We are encouraged to stay on the trail, not only to avoid stepping on and damaging the beautiful foliage (or biological soil crust), which may be to the left and right of the trail, but to minimize the risk of tripping, losing our balance on random terrain, and possibly injuring ourselves. If that’s not enough of an application of optimization, usually paths are clear of debris to maximize our comfort, and minimize the required energy to make progress along the path. It takes a lot more energy to continually step over fallen trees and branches all day long and so popular hikes are often maintained with volunteers clearing the path for others. As a species, we optimize the experience for others behind us, but what’s interesting is that most paths started out as game trails, where animals and other species would walk along these same tracks and initiated the process of breaking in these routes.
The path itself might go up and down multiple times and we will often find ourselves minimize the slope changes along the trail. For example, most adults who are aware of conserving energy, won’t jump up onto, and then down from, rocks continuously. Children love to so this and thus are wasting a lot of energy in the process. But we all have to learn. After enough time hiking, we become natural smoothers of the uphill and downhill trajectory of the trail. The most extreme case is when we step over deep crevasses or walk around a tall rock directly on our path. Why would we go down just to come back up again in such a short distance? We know that the optimal route is over or around these obstacles and not following the jagged terrain precisely. This noise in the path are miniature peaks and valleys which can be safely ignored in the smoothing function of where we place our steps.
Speaking of big uphills, humans will defer to switch backs to optimize the upward progression. We might not want to use our hands to scramble up a steep incline so instead we hike back and forth, crossing left and right, and covering more distance but at a lower slope and at an elevation gain that takes longer but at a lower power output. If possible we optimize this process even further by hiking on the outside of the turns of the switchbacks, where the rate of increase would be minimized because of a larger distance. In other words, we seek to reduce the gradient of ascent (or even descent) to maintain our pace, reduce fatigue, or avoid injury. However, we all know those people (and perhaps we are those people) who cut the switch backs short and opt for a steeper incline. I’ve been tempted myself to take those short cuts. It looks shorter (and it is shorter), but the gradient, slope, or terrain is often worse and I find myself often regretting my decision to cut corners. It’s also discouraged on many trails as it can reduce the structural integrity of the ground holding up the switchbacks and can accelerate erosion and cause safety risks. Still, in many circumstances, hikers will optimize for their time, at the expense of energy or comfort, by taking those shortcuts.
Enough about humans, let’s turn to some animals.
The best time to see animals, like deer, moose, and even bears, while hiking, is early morning or evening. Why is this? They are optimizing the energy they use to stay either warm or cold at different times of the day or seasons. For example, during the heat of the day, it’s best to rest in the shade and conserve energy, which is why we don’t see wildlife as much during the middle of a day hike. In the morning and evening hours, the temperature is best for catching prey or finding food where there is some light but it’s also not too hot. All the animals that didn’t follow this optimizing strategy are, well, dead. They didn’t live long enough to pass on their suboptimal strategy of wasting energy during the midday. Only the animals that take it easy during the day survive to adulthood and pass on their strategies to their children. Bears take this to the extreme during winter when they optimize their energy conservation while they hibernate.
The opposite is found in animals that are cold-blooded. I was once told that venomous snakes will rarely attack and bite you in the morning. They are still too lethargic, weak, and warming up to able to move quickly and strike you. Snakes will have to wait until the sun has warmed them up a bit more before they become active and more mobile. The optimizing strategies are different than mammals but they clearly both work.
Continuing along our hike, we often will see birds flying in the sky, and chirping in the trees. Birds are fascinating for countless reasons but two of their most obvious optimized features are their hollow bones and the aerodynamic shape of their wings. Minimizing the weight that one has to lift during flight is an evident objective. This can be accomplished by optimizing the structural components, i.e. bones, to be just strong enough to hold up the bird’s weight, but at the smallest mass possible. A particular flavor of optimization, called topology optimization, is partly inspired by this quasi-hollow structure, where cavities are found in structural components similar to the bones of some birds. Of course there are birds with more solid bones but their bone designs are for different purposes such as diving into water, defending their families, or attacking prey.
Likewise, the curvature of bird wings has inspired man-made airfoil shapes. It’s amazing to think about the multiple generations of birds over eons of time where wings were slowly optimized with small mutations and incremental advantages to form a more aerodynamic wing. Those birds with beneficial mutations that made flight more efficient could find more food and could feed their young more optimally. The existence and the optimization of a wing remains in my mind one of the marvels of the animal kingdom. (The eye, in all of its varieties found in the animal kingdom, is my other favorite).
There are many other animal examples, and lots of nature shows detailing them, but let’s finish off with some plants.
Trees are wonderful gifts to so many other organisms in the world. Trees provide shade, wood, fruit, fire, furniture, protection, and … maple syrup. The list goes on and on. But how they achieve such an amazing resume of benefits is truly remarkable. Trees are replete with optimized subsystems, from the roots in the ground to the process of photosynthesis in their leaves. One phenomenon I love to observe in some types of trees is called “crown shyness.” These trees will extend their branches outward but will not overlap or touch the branches of a neighboring tree. The result is a beautiful view when looking up with gaps between trees and some serious contemplation about optimization. Do they do this to maximize sunlight and reduce the shading of their tree neighbors? Do they do this to avoid damaging each other’s branches in windy conditions? Is there some other reason this behavior is optimal?
I’m equally amazed with flowers. How did so many colors and shapes become so abundant? Why are there different ways, methods, and techniques they each use for pollination or propagation? The variety of optimal strategies is remarkable. Some of my favorites are the bee orchid, rafflesia arnoldii, and of course, venus fly traps. Bee orchids have a part that mimics the look of female bees, for the, not surprising, optimal strategy to attract male bees and increase the chance that they’ll be pollinated. Rafflesia arnoldii have massive flowers up to almost a meter in diameter and they stink like rotting flesh to attract flies and other bugs to help with pollination. Finally, the carnivorous venus fly trap is just simply astounding. The way in which it entices bugs to sample some nectar and then trap it for a slow digestion period is incredible . How the evolutionary process advanced from the initial organism billions of years ago to this current iteration would be fascinating to observe.
Optimization, or, at a minimum, the principles of optimization, are found everywhere in nature. Even a short walk, along with the smallest amount of awe and wonder, will inevitably cause us to ponder optimization whether we realize it or not. As designers, we should develop this attitude of awe directed toward other people, other processes, and other phenomena. Our society has designed and will yet design many things based on nature. There is a thing or two we can learn from nature’s billions of years of experience designing and optimizing.
