Their reproductive lives are so drawn out that surely there's intense pressure to stay healthier for longer. They reach sexual maturity as late or later than us

Their reproductive lives are so drawn out that surely there's intense pressure to stay healthier for longer. They reach sexual maturity as late or later than us, gestate for at least twice the duration, care for their young for a long time, have relatively few offspring, and can keep going, sometimes, till their sixties. All that extra time to raise few children means evolution must select those who can keep ahead of attrition, and it's a marathon not a sprint.