I like to think that when Medawar and his colleagues showed that immunological tolerance could be produced experimentally the new immunology was born. This is a science which to me has far greater potentialities both for practical use in medicine and for the better understanding of living process than the classical immunochemistry which it is incorporating and superseding.
What makes me so certain that the natural human lifespan is far in excess of the actual one is this. Among all my autopsies (and I have performed over 1000), I have never seen a person who died of old age. In fact, I do not think that anyone has ever died of old age yet. We invariably die because one vital part has worn out too early in proportion to the rest of the body.
The decrease in incidents of death from cancer is largely attributable to new medicines or therapeutics. Perhaps a third is attributable to changing our environment, and that includes of course smoking which I believe accounted for probably 20 percent of deaths from, certainly from lung cancer, more than that from lung cancer, but from cancer overall.