Peter Medawar — Brazilian Scientist born on February 28, 1915, died on October 02, 1987

Sir Peter Brian Medawar OM CBE FRS was a British biologist born in Brazil, whose work on graft rejection and the discovery of acquired immune tolerance was fundamental to the practice of tissue and organ transplants. For his works in immunology he is regarded as the "father of transplantation". He is remembered for his wit in real life and popular writings. Famous zoologists such as Richard Dawkins, referred to him as "the wittiest of all scientific writers", and Stephen Jay Gould, as "the cleverest man I have ever known"... (wikipedia)

I cannot give any scientist of any age better advice than this: the intensity of a conviction that a hypothesis is true has no bearing over whether it is true or not.
Today the world changes so quickly that in growing up we take leave not just of youth but of the world we were young in.