Nature has given every species an intrinsic life span. Life span is a bit like an upper bound to life expectancy: if you got every member of a species healthier and healthier, life expectancy of that species would constantly increase, but eventually be bound by life span.
Every species has a different life span: for flies, it’s just a couple of days, for bowhead whales it’s 200 years. For humans, biologists have found that up until the 1960s, life span was around 89 years. This means that if we kept improving our health systems, the world population’s life expectancy would converge to our species’ life span of 89.
So how did we break the limits of life expectancy?