That's the question suggested by a new paper in the American Economic Review. Here's the abstract:
We study the extent to which eminent scientists shape the vitality of their areas of scientific inquiry by examining entry rates into the subfields of 452 academic life scientists who pass away prematurely. Consistent with previous research, the flow of articles by collaborators into affected fields decreases precipitously after the death of a star scientist. In contrast, we find that the flow of articles by non-collaborators increases by 8.6% on average. These additional contributions are disproportionately likely to be highly cited. They are also more likely to be authored by scientists who were not previously active in the deceased superstar's field. Intellectual, social, and resource barriers all impede entry, with outsiders only entering subfields that offer a less hostile landscape for the support and acceptance of “foreign” ideas. Overall, our results suggest that once in control of the commanding heights of their fields, star scientists tend to hold on to their exalted position a bit too long.
This seems relevant to conversations about life extension. I'm uneasy about life extension research, but one of the arguments I've heard given for it is that when people die, we lose all of their knowledge and wisdom. This article suggests that maybe having people live for longer would hold other sources of knowledge and wisdom back.
I think a lot of this comes down to social factors rather than star scientist's productivity decreasing with age.
At least in neuroscience, and probably in the life sciences more broadly, PIs who are very influential in a subfield (or who start a new one) tend to be the go to people for a topic and often become the gatekeepers, so work on that topic is generally done in collaboration with them. Junior scientists (even ones trained by that PI) will usually try to establish a unique research focus that avoids conflict with the exisiting star PIs, even if that means they end up working in a less promising area.
I haven't read the linked paper, but I assume that one factor leading to increase in productivity is simply an increase in good people working in a promising research field where the gatekeeper was removed. In principle, this doesn't need the death of a star scientist to achieve.