The Evolution of Throwing
Humans are the only species that can throw objects both incredibly fast and with great accuracy. This unique throwing ability may have been critical to the survival and success of our hominin ancestors, helping them to hunt and protect themselves. Our research asks: How are humans able to throw so well? When did this behavior evolve? Was throwing important in our evolutionary past?
Our team, led by Neil Roach, has found that humans are able to throw projectiles at incredible speeds by storing and releasing energy in the tendons and ligaments crossing the shoulder. This energy is used to catapult the arm forward, creating the fastest motion the human body can produce, and resulting in very rapid throws. We show that this ability to store energy in the shoulder is made possible by three critical changes in our upper bodies that occurred during human evolution: 1. the expansion of the waist, 2. a lower positioning of the shoulders on the torso, and 3. the twisting of the humerus (bone in the upper arm). All of these key evolutionary changes first appear together nearly 2 million years ago in the species Homo erectus.
We propose that this ability to produce powerful throws was crucial to the intensification of hunting that we see in the archaeological record at this time. Success at hunting allowed our ancestors to become part-time carnivores, eating more calorie-rich meat and fat and dramatically improving the quality of their diet. This dietary change led to seismic shifts in our ancestors’ biology, allowing them to grow larger bodies, larger brains, and to have more children.
Armed with nothing but sharpened wooden spears, the ability to throw fast and accurately would have made our ancestors formidable hunters and provided critical distance between themselves and dangerous prey.
- Humans are remarkable throwers, and the only species that can throw objects fast and accurately.
- Chimpanzees, our closest relatives, throw very poorly, despite being incredibly strong and athletic.
- We have shown that humans produce high-speed throws by storing elastic energy in the tendons, ligaments, and muscles crossing the shoulder.
- When this energy is released, it powers the rapid acceleration of the arm and the projectile, including the fastest motion the human body produces.
- Three changes to the anatomy of the torso, shoulder, and arm that occurred during human evolution make this elastic energy storage possible.
- These morphological changes are first seen together 2 million years ago in Homo erectus.
- Concurrent with these changes, archaeological evidence of more intensified hunting behavior suggests that throwing may have played a vital role in early hunting.
- Hunting had profound effects on our biology. For example, by improving diet quality our ancestors were able to grow larger brains leading to cognitive changes such as the origins of language.
- Today, most throwing athletes throw much more frequently than our hominin ancestors did and, accordingly, frequently suffer from overuse injuries.
Roach, N.T., Venkadesan, M., Rainbow, M.J., Lieberman, D.E. (2013) Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo. Nature 498, p. 483–486.