An internationally respected tuberculosis researcher in the Otago microbiology and immunology department, Prof Cook said his early work as a research assistant had proved "crucial" for his later development.
He was addressing about 310 people who had graduated in person in many disciplines, including biomedical sciences, health sciences, and medicine at the first of two ceremonies at the Dunedin Town Hall, at 1pm on Saturday. Prof Cook said that by the age of 21, and having done the Otago research assistant job after his first degree, he realised he did not "like the constraints" of a nine-to-five job.
He had "wanted the freedom to explore my own ideas, not those of other people" and "wasn’t good at being told what to do by others and sticking to the rules".
He urged graduates not to settle for second best and warned they would "never find true happiness and fulfilment" by doing so.
"I loved the roller-coaster road of scientific discovery — massive highs and lows, but always the thrill of discovering something new every day."
He urged graduates to "back yourself to be a force on the international stage" and to work on something "of global significance".
When he woke each morning, he realised that "5000 people will die today of a curable disease I work on".
"Only by joining the global fight and linking with the international Tb research community can our work in New Zealand be part of something bigger that could lead to the eradication of this disease in humans," he said.
Prof Hamish Spencer, of the Otago zoology department, told another group of Otago graduates attending a 4pm ceremony that his first Otago degree had given him "many of the tools" he needed to undertake his overall career journey.
He had undertaken further study at Harvard University "even though it was scary to leave everything that I knew behind" and to go somewhere where he knew almost no-one.
Such opportunities involved risk and moving "out of your comfort zone".
In the United States at that stage, there were armed police and Ronald Reagan was president. But his time at Harvard had proved "utterly life-changing" and had "provided the foundation for an amazing career".
Addressing more than 330 science graduates, Prof Spencer congratulated them on their achievements and told them they were "near the beginning of a journey", which would take them to some places that were "surprisingly challenging" but, perhaps, would also be "unexpectedly rewarding".
Their Otago University degree gave them a head start, and he urged them to "enjoy the journey".