The decision by Labor MP Harry Jenkins to retire at the next election should be put in a broader context. The former Labor speaker has not only been a member of the House of Representatives for the Victorian seat of Scullin since 1986 but the Jenkins father-and-son team has represented Scullin for 40 consecutive years since 1972. His father, Dr Harry Jenkins, was also speaker, during the early years of the Hawke government.

Longevity in office is usually praised rather than criticised. Furthermore Jenkins is generally regarded as a good bloke. That much was clear by the sympathetic reactions when he was stood aside by the Labor Party to accommodate Peter Slipper as Speaker in November last year.

But his case raises bigger democratic issues which should be discussed before we conclude that the Jenkins family's ownership of Scullin has been a good thing.

The first is about the desirability of political families in parliaments. There have been plenty of examples of them in modern Australian politics. The Labor Party has had the Creans, father and son, and the Beazleys, father and son. On the Coalition side there have been the three generations of the Anthonys in Richmond, NSW, for the Country/National Party and the three generations in colonial and federal politics of the Downers in South Australia. Independent Bob Katter, member for Kennedy in Queensland since 1993, is the son of Bob Katter senior, once minister for the army, and the member for Kennedy 1966-90.

The current NSW Treasurer, Mike Baird, is the son of former state and federal Liberal MP, Bruce Baird. The Queensland LNP Premier Campbell Newman is the son of husband and wife federal Liberal MPs Jocelyn and Kevin Newman.

There are many more political families , including the Labor Joneses, Fitzgibbons and Fergusons in NSW and the Liberal Courts (Western Australia), Wilsons (South Australia) and Hodgmans (Tasmania).

The positive way of looking at this is that there is a political gene that not only attracts members of the same family to politics but gives them the personal attributes to succeed.

I've had an interest in political families for some time and, on a previous occasion when I have written sceptically about them, a respected correspondent put it to me very strongly that I shouldn't be surprised or concerned because all of the professions, including medicine and law, and many of the arts, like painting, exhibit the same characteristics.

In this interpretation families are breeding grounds for politics just like other professions. They drink politics from their mother's milk, are encouraged by family dinner table discussion, and are given practical assistance like being enrolled early in their family's political party. Most importantly, they observe role models of a life of public service by their parents and even grandparents and are taken along for the ride.

They same is true to some extent of sports men and women. At this Olympics there have been obvious examples of the inheritance of the physical and mental attributes to do well. Kim Crow, the successful single and double sculler, is the daughter of the former AFL footballer, Essendon's Max Crow. Aidan Roach, the goal-scoring member of the men's water polo team is the son of Steve ''Blocker '' Roach of NRL and Australian Kangaroos fame. The silver-medal-winning slalomist Jessica Fox's mother and father were both Olympians. This success across generations is to be applauded. However, in all walks of life the dominance of families can be negative if this ever leads to manipulation of the system.

This involves insiders advantaging family members over others. There was some talk in the lead-up to the Olympics that this had even happened in the selection of the Australian team in the case of equestrian members from the same family, though the son of men's hockey coach Rick Charlesworth narrowly failed to make his father's team.

As far as political life is concerned the same is true, perhaps even more so. There is a potential darker side to political families if politics becomes exclusive rather than inclusive. The comparison with other professions and activities may not hold up as politics is about democracy and democracy implies rotation of representatives.

This starting point feeds into two debates about democracy, one about the nature of representation and the other about the decline of modern political parties.

Representation has several elements, one of which is practical and technical while the other is about being representative of the community. MPs from political families are probably good at the practical aspect of representing constituents because they have seen how it should be done. Certainly there is no reason why they shouldn't be as good as anyone else.

However it is healthy in a democracy if representatives over time represent a wider section of the community, not just in terms of party representation but in terms of not being an exclusive club drawn from the one family. Representation should be spread around generously.

Modern political party membership is shrinking amid claims that party advancement is closed and incestuous. Factional politics is one element. Political families, in which successive generations of the one family are chosen to be representatives, reinforce this exclusive image.

The selection process may be all above board, and there is no suggestion that it has not been in the case of Harry Jenkins senior and junior. Nevertheless it may still be the result of a closed political process.

Forty years is a long time whatever the name of the family. No matter how good the individual MPs may be, politics is better off without dynasties.

John Warhurst is an emeritus professor of political science at the Australian National University.

John.Warhurst@anu.edu.au