There's a report in The Times covering a study done by Satoshi Kanazawa studying the age of peak achievements for high-flying (male) scientists:
In the study, published in the Journal of Research in Personality, Satoshi Kanazawa, of the University of Canterbury, examined the biographies of 280 great scientists. He found that 65 per cent of the mostly male researchers had made their biggest discovery before their mid-thirties. Their "productivity curve" follows almost exactly that of male common criminals, whose illegal activities peak in late adolescence and early adulthood. The explanation, according to Dr Kanazawa, is simple: they are seeking to impress women with their virtuosity. "They do whatever they do to get laid," he said. "Scientific productivity indeed fades with age. Two thirds will have made their most significant contributions before their mid-thirties." Marriage, he found, dampens men's drive in science and crime. Within five years of marrying, almost a quarter of the scientists had published their last work of any great importance.
Hmm. Since I'm over thirty and married, this doesn't bode well for me. However, I am also female, so maybe there's a different trend. Apparently Kanazawa didn't have enough data on high-flying female scientists (this is — in itself — rather depressing), but he does cite Marie Curie as perhaps bucking the trend (isolating radium at the age of 43, and while married), but then the article mentions that Rosalind Franklin (who imaged the structure of DNA using X-ray crystallography), was only in her early 30's when she made the discovery. Sadly, it neglects to mention that she died tragically early at the age of 37, so who knows what she might have been capable of later in life.
I don't even think that these findings are very fair on men. After all, if you make one of the 20th Century's most important scientific findings at the age of 251, all of your subsequent research is likely to be an anti-climax.
1James Watson, who worked out the structure of DNA with Francis Crick, along with a lot of help from Rosalind Franklin and her colleague Maurice Wilkins.