I read one a few years back - the average man survives 37 years past the birth of his last child....

And this is apparently constant (to a point)...While anecdotal, I have seen a lot of guys die in their late 50's - early 60's having been done with all their kids by their mid-late 20's...and other guys who had kids in their late 40's and on, live until 90...

Something about the desire to hang around long enough to see them fend for themselves...(socio/evolutionary/genetic)

Almost parallels the studies that say on average people live 10 years (on average) past retirement date - regardless of when they retire....