If a world record for academic promptness exists, it may have been broken this week by the scholars and scientists who convened in Washington for the Seventh International Smithsonian Symposium. Eighteen of the 19 papers scheduled for delivery were mailed in either ahead of time or on time.

With the momentum of that rare enthusiasm behind them, the assembled intellectuals are discussing the theme of the symposium, "How Humans Adapt: A Biocultural Odyssey."

The opening lecture was delivered Sunday evening by Dr. Rene Dubos, the experimental microbiologist of the Rockefeller University in New York. Speaking in Baird Auditorium in the National Museum of Natural History, Dubos was introduced by former senator J. William Fulbright, who was garbed in a scarlet robe that a lay cardinal might wear. Fulbright, in commenting that 80-year-old Dubos was anything but a newcomer to the scene, remarked drolly that the much-honored guest speaker was awarded a PhD by Rutgers University "during the now fashionable administration of Calvin Coolidge."

The remark evoked knowing laughter, followed by a rush of modest applause. Fulbright, riding it, added: "I sometimes long for Calvin."

Dubos, whose paper was titled, "Technological and Social Adaptations to the Future," spoke for about 30 minutes. He touched on the potential horrors of nuclear war and the current suffering caused by youth unemployment.

Hailed by many in Western society as both a sage and an optimist, the French-born Dubos concluded his lecture on a note of hopefulness: "Wherever human beings are involved, social adaptations and evolutions make it certain that trend is not destiny, because life starts anew, for human beings, with each sunrise."

For others in the conference, the sun may be rising daily but a cloud covering persists. Yesterday afternoon, James V. Neel, a professor of human genetics at the University of Michigan medical school and whose work among the Yanomamo Indians inspired the adaptation theme of the meeting, said that "there is no magic genetic endowment waiting to capitalize on as times get tougher. For the immediate future, we will make do with primate brains which have undergone some poorly understood modifications . . . The view of the immediate prospects for the human odyssey which our experience with primitive cultures -- combined with an analysis of our current trends -- thrusts upon me is gloomy."

Earlier yesterday, Stephen Toulmin of the University of Chicago, in a paper titled "The Natural and the Human Future," said that "the same coin has another less gloomy face. Alongside all these legitimate fears, there has grown up a novel recognition that our destiny is largely in our own hands. Unthinking expansion and uncontrolled appetites may have put at risk both human life and the biosphere itself, but intelligent analysis and conscious human restraint may undo that damage. Indeed, the damage can perhaps be undone only in that way."

The papers of the symposium, which began late Sunday afternoon with a procession of the scholars across the Mall and which ends tomorrow night at 8:30 with a public lecture in Baird Auditorium by Edward S. Ayensu, will be gathered into a book to be published by the Smithsonian Institution Press.