During the several-million-year journey our ancestors made from climbing trees to living their lives primarily on the ground, they evolved two traits that would ensure that our species thrive: upright posture and the ability to hurl a 100-mile-per-hour fastball. Humans are able to throw much harder and more accurately than any of the great apes, despite having much less powerful muscles than many of them. This key adaptation may have contributed greatly to Homo sapiens’ success as hunters and, in turn, to our success as a species, according to a team of researchers led by Neil Roach of George Washington University. The team studied 20 experienced throwers to uncover the reasons for this unique ability, and to understand when it may first have evolved. The secret seems to lie in our shoulders.

“For the brief instant that the throw occurs, you are storing about 50 percent of the energy that you need to create this tremendous velocity in your shoulder,” says Roach, who conducted the research while at Harvard University. When the participants cocked their arms back to throw, the tendons and ligaments in their shoulders stretched and stored up energy that was then released in a burst. Roach identified three anatomical traits that humans evolved to perform this feat—torsos that move independently of our waists, shoulders located on the sides of our torsos, and upper-arm bones shaped to increase our ability to stretch the shoulder tendons and ligaments.

“I can’t think of a better design,” says Glenn Fleisig, research director of the American Sports Medicine Institute. Fleisig has spent much of his career working on shoulder injuries. “I might make the shoulder socket deeper,” he says. “That would make it harder to have a shoulder injury, but you would have less flexibility to do other tasks.” Shoulder evolution involved a similar trade-off, as hominins lost some of their ability to move easily through trees in exchange for the improved ability to throw.

When the modern shoulder first evolved is a matter of some dispute. According to Roach and coauthor Dan Lieberman of Harvard University, the traits for modern throwing came together in Homo erectus no later than 1.6 million years ago, and possibly much earlier. Susan Larson of Stony Brook University, however, reconstructs the H. erectus shoulder differently and believes that Homo heidelbergensis was the first hominin to have modern throwing ability.

Roach and Lieberman regard the evolution of the shoulder as one part of a suite of anatomical changes that helped hominins to move out of the trees to gather new foods and begin hunting. They see natural selection acting on these new behaviors and driving further evolutionary changes that made us better runners and throwers. “There is selection for the hunting and gathering way of life,” says Lieberman.

Starting in July 1776, American troops under General Philip Schuyler built a massive fort on Rattlesnake Hill, overlooking Lake Champlain in western Vermont. The purpose of the fort, along with the old French Fort Ticonderoga across the narrows in New York, was to prevent a British invasion from Canada. On July 28, the Declaration of Independence was read to the assembled soldiers, and the hill acquired the name it holds today: Mount Independence. In early July 1777, the British drew close. With too few American soldiers, Major General Arthur St. Clair and his officers decided to withdraw. Though there was an uproar about the loss of the forts, this decision, and a successful rearguard action at the Battle of Hubbardton, saved the American Northern Army for later victories at Bennington and Saratoga. Today, Mount Independence is a Vermont State Historic Site and one of the best-preserved Revolutionary War–era archaeological sites in America. According to Elsa Gilbertson, the regional historic site administrator, the history of the site is visible among hundreds of acres of forests and meadows. 

The site

The fort at Mount Independence was a three-level defensive system that made use of the rugged topography. There were batteries, a star-shaped fort with barracks, three brigade encampments, the largest American hospital built during the Revolution, blockhouses, storehouses, wharves, and a bridge to Fort Ticonderoga. Along six miles of hiking trails, visitors can see the remains of many of these structures, as well as stunning vistas of Lake Champlain. In 1996, a museum was built there in the shape of a bateau, a flat-bottomed boat commonly used during this period, to symbolize the strategic and economic importance of Lake Champlain. Exhibits lay out the role of Mount Independence and the life of its soldiers through artifacts excavated there, including a cannon, logs from the bridge, ammunition, construction tools, buttons, cuff links, and medicine cups. 

While you’re there

The town of Orwell in Addison County is full of historic buildings, including the unique First National Bank of Orwell, which has been in business at the same location since 1863. The charming bandstand on the green is perfect for a picnic. Visitors can continue on to the Hubbardton Battlefield State Historic Site to see where the Americans, British, and Germans fought after the withdrawal from the forts. And to the north is the Chimney Point State Historic Site, the location of a 1731 French fort.