"Usually a man who is entirely healthy in his early 80s has demonstrated his survival prowess" and can live much longer, he said. People of privilege have better odds because they have access to good food and health care, and tend to lead clean lives.
"Even in the 1500s and 1600s there were popes in their 80s. It's remarkable. That would be today's centenarians," Perls said.
Arizona Sen. John McCain turned 71 while running for president in 2007. Had he won, he would have been the oldest person elected to a first term as president. Ronald Reagan was days away from turning 70 when he started his first term as president in 1981; he won re-election in 1984. Vice President Joe Biden just turned 70.
In the U.S. Senate, where seniority is rewarded and revered, South Carolina's Strom Thurmond didn't retire until age 100 in 2002. Sen. Robert Byrd of West Virginia was the longest-serving senator when he died in office at 92 in 2010.
Now the oldest U.S. senator is 89-year-old Frank Lautenberg of New Jersey. The oldest congressman is Ralph Hall of Texas who turns 90 in May.
The legendary Alan Greenspan was about to turn 80 when he retired as chairman of the Federal Reserve in 2006; he still works as a consultant.
Elsewhere around the world, Cuba's Fidel Castro — one of the world's longest serving heads of state — stepped down in 2006 at age 79 due to an intestinal illness that nearly killed him, handing power to his younger brother Raul. But the island is an example of aged leaders pushing on well into their dotage. Raul Castro now is 81 and his two top lieutenants are also octogenarians. Later this month, he is expected to be named to a new, five-year term as president.
Other leaders who are still working:
—England's Queen Elizabeth, 86.
—Abdullah bin Abd al-Aziz al-Saud, king of Saudi Arabia, 88.
—Sabah al-Ahmad al-Jaber al-Sabah, emir of Kuwait, 83.
—Ruth Bader Ginsburg, U.S. Supreme Court associate justice, 79.
Associated Press writers Paul Haven in Havana, Cuba; David Rising in Berlin; Seth Borenstein, Mark Sherman and Matt Yancey in Washington, and researcher Judy Ausuebel in New York contributed to this report.
Marilynn Marchione can be followed at http://twitter.com/MMarchioneAP