That decision changed the course of their lives. The same could probably be said for many of the Peace Corps' more than 200,000 volunteers, many of whom will descend on Washington, D.C., this weekend for the Peace Corps 50th anniversary celebration, Sept. 24.
Shirley, now 63, developed an affinity for Africa when he represented Tanzania in the Model U.N. in high school. That interest grew at the California Institute of Technology, and though he applied to graduate schools as well, his first choice came through when he was accepted into the Peace Corps.
Within a few weeks of graduating from college in 1969, he arrived in Sierra Leone.
Shirley taught high school math in the town of Bonthe for two years and ended up staying for a third year to help institute a curriculum change that was sweeping across West Africa.
Though he never intended to be a math teacher — let alone a teacher of math teachers — Shirley briefly came back to America before returning to Africa, this time to train math teachers at Ahmadu Bello University in Nigeria
"I went to Nigeria only intending to stay for three years, and I ended up staying for 15," he said. "Partially because I liked the job, but also because life caught up with me."
Life, as it turned out, became a Ghanaian woman named Alberta Ohenewah, whom he married and had two children with.
They lived in Nigeria until 1988, when he decided to move his family back to America. He had finished his doctorate and believed American high school would be better for his children should they wish to go to college here.
More importantly, after nearly two decades as a math teacher in West Africa, Shirley felt his work there was finished.
"When I first went to Nigeria, the university was staffed by ex-patriots," Shirley said. "But Nigeria was growing and producing its own staff. Most of the teaching staff was Nigerian. There weren't many Americans or Europeans left. (Leaving) seemed like the right thing to do."
The trans-Atlantic interview process proved difficult, but Shirley swung a one-year teaching gig at Northern Illinois University, and from there, landed at Towson University, where he began as a math professor and has ascended to acting dean of graduate studies.
"Many times people say how the Peace Corps changed their lives," Shirley said. "In my case, it's more than most. I wasn't really planning a career in math education, and it's been my career ever since."
Cook's decision to join the Peace Corps was a bit more spontaneous. After graduating from the University of Richmond in May 1965, she intended to go to a seminary for her master's degree in church music and become a church choir director.
Instead, she married Richard Cook on Aug. 14, 1965. The newlyweds reported to Peace Corps training 23 days later.
"I would have never done that alone," said Cook, now 67. "But that's what he was going to do, so if I wanted to marry him, I had to join the Peace Corps."
Six married couples began training at Camp David, a jungle camp in Puerto Rico that provided intensive language training and cultural lessons. Just one other couple — another pair of newlyweds — made it through the three-month training session.
From there, the couple reported to an urban slum in Panama. Richard Cook helped build concrete paths and steps in the hillside village, allowing residents to retrieve water without slipping down the muddy slopes.
Barbara Cook taught music and introduced the village women to family planning. She planned to teach sewing, only to learn the women knew much more about it than she.