Note: This is the sixth chapter of my serialized book Healthy Movements for Human Animals. You can find an archive of previous chapters here.
In the previous chapters, we explored primal movement patterns that involve close proximity to the ground, such as rolling, crawling, and squatting. Now we shift our focus from Ground World to Tree World, looking at the movement patterns that first emerged when our ancestors adapted to life in the trees: reaching, hanging, and climbing. This chapter focuses on the most primal of these movements, which is reaching.
The ability to extend the hand far from the center of the body to grasp distant branches was an essential survival skill for our primate ancestors. Adapting to this challenge reshaped their entire anatomy, especially the upper body. Overhead reaching was especially transformative, leading to the evolution of vertical spines. Where the hand went, the body followed.
For human infants, reaching to grasp objects is one of their first intentional movements and a key developmental milestone that coordinates the hand with the eye and upper spine. It precedes even rolling and crawling, indicating its status as one of our most fundamental movement patterns.
Because reaching is so central to human function, it’s one of the easiest ways to evoke full-body coordination. The hand acts like a conductor’s baton, organizing distant parts of the body into unified action. Depending on its direction, a reach draws the whole body into flexion, extension, side-bending, or rotation. This makes reaching one of the simplest ways to develop coordinated spinal mobility, particularly into the extended positions that characterize upright posture.
However, the modern world is engineered to place everything within easy reach. We reach forward and slightly down hundreds of times daily to access laptops, phones and coffee mugs, but rarely up, back, or to the sides. The body follows the hand, and in the modern world, the hand is always directly in front of us. It’s no surprise that our bodies are following—head and shoulders forward, chest collapsed. The easiest way to address this deficiency is to engage in varied reaching, especially upward.
In this chapter, we’ll explore how reaching emerged as our ancestors adapted to arboreal life, examine its role in infant development, and provide exercises that restore varied reaching patterns. It is one of the simplest ways to develop functional upper body and spinal mobility. Combined with the variable squat sitting discussed in the previous chapter, these movements provide nearly everything you need for full-body functional mobility.
The evolution of reaching
The great majority of animals that climb trees (e.g., squirrels, bears, raccoons) use claws to grip bark. This allows them to climb in a way that is not much different from how they walk over the ground. For them, climbing is much like vertical crawling.
Our ancestors, however, evolved a different locomotive strategy when they moved into the trees about 55 million years ago: grasping hands and feet with flattened nails instead of claws. This technique, called frictional gripping, is almost unique to primates among mammals. Grasping hands allowed an extraordinary diversity of postural and locomotor behaviors, such as reaching for distant branches and fruits, hanging while resting, and swinging hand-to-hand. These abilities were made possible by major transformations of the upper body, especially the shoulder.
Terrestrial quadrupeds have shoulders designed to absorb the compressive forces of walking. Their shoulder sockets point downward and forward, and the humeral head sits in a deep socket for stability. The head is shaped like a cylinder, which favors movement forward and back while limiting motion side to side.
Primates evolved a different design that allowed reaching in many directions, especially overhead. The humeral head became more round, and the socket shallower, increasing freedom of movement. The socket also rotated upward and outward, facilitating overhead and lateral reaching. With less bony stability, primate shoulders relied more on the rotator cuff muscles for support.
As apes evolved, the thorax became broader and flatter, allowing the scapula to migrate from the side of the ribcage toward the back, where it could move more freely in support of varied reaching movements. The scapula also gained greater range into elevation, upward rotation, and posterior tilt—all of which improved upward reach. Meanwhile, the thoracic and lumbar spine, along with the hip joints, gained additional range into extension and rotation, further enhancing the reach of the hand.
Importantly, these gains in mobility were not just about range of motion, but also variability in how that range could be achieved. Unlike hinge joints like the knee or elbow - which offer large ranges of motion but few degrees of freedom - the shoulder complex is capable of thousands of different combinations of movements at the shoulder joint, scapula, and spine. This means that a particular target can be hit with precision from different postures, using different trajectories, and different rotations of the hand.
This freedom of movement created a corresponding challenge for the nervous system. Primate eyes moved forward and closer together, improving depth perception for judging distances to branches and fruits. The visual areas of the brain expanded, enhancing hand–eye coordination. Primates also developed dedicated brain circuits for guiding the hand through space.
The result is that reaching to a target became one of the most coordinated and precise movements that humans make. When you reach for an object on a high shelf, the thoracic and lumbar spine, pelvis, knees, and ankles extend in a smooth sequence. When you reach across a table for a glass of wine, the hips flex to push the shoulder forward. Accuracy requires orchestration of nearly every joint in the body—wrist, elbow, shoulder, scapula, spine, ribs, and even hips and ankles. Of all the intentional movements humans perform, few so effortlessly recruit the entire body into coordinated action.
Development of reaching
Reaching appears far earlier on the developmental timescale than on the evolutionary timescale. Our ancestors spent millions of years perfecting quadrupedal locomotion before they climbed trees and began reaching overhead. But infants start extending the hand away from the body to reach objects at about 3-4 months, well before they can roll efficiently or crawl. This reveals how fundamental reaching is to human function. The nervous system prioritizes the ability to extend the hand toward targets above nearly every other movement skill. And it uses a wide variety of patterns to accomplish this task.
When babies reach forward while lying on their stomach, the spine and hips extend; reaching while sitting requires flexion; reaching to the sides or at diagonals incorporates rotation and side-bending. Each variation teaches the nervous system how different body segments—shoulder, scapula, ribs, spine, and pelvis—must organize around the simple intention of placing the hand on a target.
Reaching also drives other developmental milestones. Infants often roll for the first time in response to the impulse to reach a toy that sits just beyond their grasp. The first attempts at crawling emerge when reaching while prone. Even the transition to standing begins with upward reaching—pulling to stand on a couch or crib rail (as discussed in the previous chapter on squatting).
The challenge of reaching
To understand the benefits of reaching as an exercise, we need to examine what it demands from the body. Reaching primarily challenges mobility and coordination. Here are some relevant details.
