What should be the role of the wise elderly scientist who, despite his or her age and failing pipetting skills, continues to make legitimate scientific contributions? Are senior-citizen scientists an asset, or are they obstacles to the hiring of new bright young minds?

In a Commentary in this week's issue (page 588), 66-year-old developmental biologist Peter Lawrence of the University of Cambridge, UK, staunchly defends the elderly scientist. He cites the long career of fly geneticist Seymour Benzer and the exploits of 80-year-old Nobel laureate Sydney Brenner, who was recently hired by the Howard Hughes Medical Institute's Janelia Farm campus in Ashburn, Virginia.

Lawrence criticizes the mandatory retirement ages that apply in many universities and for government employees in Europe. Not only is it discriminatory, he argues, but it impedes making commitments to graduate students and diminishes negotiating power. Some institutions do allow scientists to apply for extensions, but in Germany, for example, philanthropic foundations have had to start special initiatives to continue to fund eminent scientists due for retirement (see Nature 445, 334–335; 2007). Meanwhile, the United States, with a law that bans mandatory retirement ages, has for years benefited from an 'elderly brain gain'. Accomplished scientists attracted across the Atlantic help to buoy many a university's standing.

But could less-capable elderly scientists hang around too long? Keeping on older scientists could, in principle, make funds and university slots harder to come by for younger scientists in a funding environment that is already difficult in places like the United States — although Lawrence dismisses this argument.

He does suggest some controversial remedies, however: scientists with retirement pensions should only get a salary supplement; tenure should not be indefinite; and each scientist should be regularly evaluated for his or her contribution and asked to go when they fail to measure up. But in the end, perhaps the only way is to let each individual decide: should I continue to trek to the lab, or should I be content to let the next generation take up the mantle?