Incidentally, female chimps seem to live 25% longer than males—imagine human women lived until 90 while men died at 71.
Arithmetic error? both 71*1.25 and 71.5*1.25 to the nearest integer are 89, not 90. The error might (low-confidence, 10%) have been caused by calculating a 12.5% increase of 80 (exactly 90) and also dividing 80 by 1.125 (~71.1).
I love the xkcd book vibes of this post.