The word “scientist” does not specify a gender. And yet, for eons — well, ever since conferences and symposiums emerged from the primordial academic soup — the majority of prominent scientific speakers and panelists have been men.

This phenomenon has been documented in studies and spawned many mocking monikers: “manference,” “himposium,” “manel.” People have tried to understand why the Y chromosome so dominates the dais and explain that there really should be more X.

Now, the effort to achieve better gender balance has a new high-profile champion: the director of the National Institutes of Health, Dr. Francis S. Collins. In a statement titled “Time to End the Manel Tradition,” Dr. Collins, who led the Human Genome Project and has been N.I.H. director for a decade, said on Wednesday he would no longer speak at conferences that do not show a strong commitment to diversifying the makeup of their panelists.

“I want to send a clear message of concern: It is time to end the tradition in science of all-male speaking panels,” Dr. Collins wrote.