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Jean Luc Picard. I'm pretty sure he was in his forties. Benjamin Sisko probably. Kathryn Janeway, if she wasn't 40 in year one, she hit and passed it. Chackotay definitely hit the mark too. Come to think of it the only Captain not 40 was Kirk, at least as the lead in a series. Hmm Beverly Crusher, Will Riker exited his 30's, I'm not nure how Deana's Betazoid half changes her aging but I do know it does. So chronologically and biologically might be different... But all in all there is a pretty good list of main characters that hit or pass 40.

According to this chronology T'Pol was born in 2088, Archer in 2111, Trip in 2120 and Travis in 2125. No mention of when Malcolm, Hoshi or Phlox were born that I could find.