Soon after I turned 40, I started experiencing back problems. I asked my brother for advice (he is a medical doctor) but didn’t quite like what I heard. “Sorry brother, our bodies are just not built for us to live much beyond 40…” he told me. If you take human evolution as a reference, he is right.
For the first 59,900 years of our existence (out of a total of 60,000), people used to live only into their 30s, at best. During the 1000 or so years that followed, there were some modest improvements raising life expectancy to 40 years. Things really changed only in the past 100 years on the backdrop of major medical and sanitation breakthroughs.