Good points.
Usually when lifespans are determined, all the infant and child deaths are figured in, but once a person attains adulthood they may live to an old age.
Just like we read that in the middle ages, or a couple of hundred years ago in our country, the lifespan was shorter. Actually many people lived to a ripe old age, but the infant mortality was higher so it brought down the average. It's not that everyone in the middle ages died at 40. I'm sure it's the same in India - there are plenty of old people there.