Six months after becoming president at Harvard University, Lawrence Summers is making ripples in faculty recruitment and retention that are attracting attention beyond the confines of the campus. He is searching for faculty members who he thinks have their best work ahead of them and is avoiding more experienced academics whose future may not be so productive — people who Jeremy Knowles, Harvard dean of arts and sciences, once described as “extinct volcanoes”.

Summers is careful to avoid saying that he is seeking younger tenured faculty, but that appears to be at least a by-product of his philosophy — 'potential' sounds suspiciously like a euphemism for 'youth'.

That's not to say that the age of tenured faculty — at Harvard or elsewhere — isn't an issue. At 47, Summers is eight years younger than the average tenured Harvard arts and science professor, and about two years younger than the US national average.

Of course, an increasingly ageing faculty isn't a problem in itself. But it can cause difficulties when tenured but unproductive professors cause obstructions for younger scholars seeking academic posts. I've heard many deans and department heads around the world wish — off the record, of course — that they had a way to remove an unproductive senior faculty member.

Summers deserves credit for making waves that could prompt other universities to consider hiring promising, if less experienced, faculty. But in the end, the decision to go for promise over the proven is a judgement call with an uncertain outcome. Even youthful volcanoes can become extinct. And dormant ones, if the conditions are right, can become active again.