A less Realistic Alternate History Idea
What If? Human Lifespans were immortal-unless-killed, something along the lines of, upon reaching physical maturity, our bodily functions DO NOT break down slowly unless we get infected by disease or viruses
Think of it like being like the Mer/Elves from Elder Scrolls who reach maturity nearly the same age as humans right before the ageing process slowing down till they only look and feel old after 4 centuries, except they remain at their physical peak(well unless they forget to exercise and eat healthy)forever
The only ways to get old would be extreme physical and/or mental stress and illness rotting the body, like how people in their twenties could look way older due to poorer health and living conditions
Would population growth and technological advancements slowed down significantly if we had lifespans like that?
Also, imagine meeting your grandparents and they look your age or only slightly older than you
Like the movie “In Time”