One of the themes of the US presidential election campaign was John McCain's advanced age. Many people wondered aloud whether a 72-year-old cancer survivor had the right profile for such a job - especially given that his pick for vice-president (and his potential replacement in extremis), Sarah Palin, had plainly only ever maintained a glancing acquaintance with national and international debates.
David Letterman joked that McCain looks like the kind of bloke who picks up his TV remote when the phone rings.
The truth is, though, that compared with some members of the US Senate, McCain is a spring chicken. Senator Robert Byrd of West Virginia, aged 91, is chairman of the powerful Appropriations Committee. He also serves as president pro tempore of the Senate, which means he is third in the line of presidential succession, after the Vice-President, Dick Cheney, and the House Speaker, Nancy Pelosi. Both of Hawaii's two senators, Daniel Inouye and Daniel Akaka, are 84. The sprightly Senator Dianne Feinstein of California may well be a candidate for governor of that state in 2010 - when she will be 77. The late Senator Strom Thurmond of South Carolina retired from the Senate a few years ago at the age of 100.
Recently Washington was riveted by the trial of Senator Ted Stevens of Alaska for petty corruption, including the receipt of holiday house improvements and a complimentary barbecue. Few people commented on the fact that this 84-year-old was simultaneously running for yet another six-year term.
Some of these legislators are not just old: they are also sick. Yet their chosen profession is demanding, exhausting and deeply important.
These are extreme examples, but the statistics bear out the general point. The average age of a US senator is 62 - a full quarter of a century older than the average age of a US citizen. When you factor in the young things in the House of Representatives, the average age of Congress comes down to 57 - but even that is one of the highest in history, and significantly higher than the Australian equivalent. On average, Australians are slightly older than Americans, yet the average age of our federal parliamentarians is 50. The longest-serving member of our lower house, Philip Ruddock, is 65. Paul Keating was 52 when he retired.
Old age should not, of course, be an automatic disqualification from high office. After all, young people don't have all the answers - a fact that is increasingly obvious to me as the years go by. With age comes experience and often wisdom. Legislatures should not be reserved entirely for callow young politicians with no outside experience.
Yet in Washington, the pendulum has swung too far the other way. The primacy of money in US politics makes it difficult to dislodge incumbents. The rules of seniority mean that some of the best jobs are reserved for people who have been around forever.
Perhaps this is the most damaging point: not just that these legislators are old, but that they have grown old in office. Byrd has been in the Congress for 55 years. Stevens has sat in the Senate for 40 years. Younger American politicos are left kicking their heels at the back of a very long queue.
The queue may be moving a little faster these days, however. There are signs that the American gerontocracy is crumbling a little at the edges.
Last month Congressman John Dingell jnr was beaten for the chairmanship of the House Energy and Commerce Committee. The fact that Dingell is an 82-year-old, 53-year veteran of the House who is recovering from knee-replacement surgery was not enough to save him. (Dingell inherited his seat from his father, John Dingell snr. Michigan's 15th congressional district has been represented by only two men since 1933, both called Dingell.) The Democratic caucus handed the job over to Congressman Henry Waxman of California, who at a mere 69 years of age has served only 33 years in the House.
Even more significant was the election of the 47-year-old Barack Obama to the White House. Much has been written about Obama's appointment of Clinton veterans (and, indeed, Clintons) to senior positions. However, he has also shown a willingness to reward merit even when it has not been demonstrated over the course of many decades.
His will be a young and very energetic administration. The Washington Post has calculated that two-thirds of Obama's White House appointees so far are his age or younger. The new chief of staff is 49 and his two deputies are 41 and 39. Obama's press secretary is 37; his ambassador to the UN is 44; his chief speechwriter is 27.
To an outsider, the age distribution in Washington is unusual. There are lots of very young people, straight out of university, and lots of older people - but not so many in between. If Obama delivers some middle-aged spread to the place, it will be a healthy thing.