Why Did Jared Diamond Start Counting Time at 89?

Jared Diamond says a sharp sense of time left has not always been part of his life. Turning 80 was not a shock. Turning 81 was a bigger shock, because 81 meant he was firmly embedded in the 80s. He already knew the life expectancy of an American man at birth is something like 78. He also knew a fact he says is not widely known: once an American man has reached 70, life expectancy is 93, because a lot of the risk is behind him. At 81 he still was not counting what he could do.

In the last couple of years, now that he is 89, he is very conscious of the time left. He wants to synthesize his understanding of New Guinea, which has 10 mountain ranges. He did the first ascents and the first ornithological explorations of several of them, and the most detailed explorations of the rest. He wants the synthesis to show what makes a species a good colonist: why some bird species are on all 10 mountain ranges and other birds are on only one. He has a unique data set. If he does not write it up while he is still alive, the knowledge will die with him, because the mountain ranges are difficult to get into.

Knowing the life expectancy numbers did not lead him to count the years at 81. The count started in the last couple of years, at 89.