In years, what do you think would be the optimal life expentancy for humans? In other words, how long would you like human beings to live on average? This is a philosophical question. If humans had bodies designed to live much longer than they do now, the world and a human's life would be very different. Consider this in your answer.
For recent years in Swaziland life span is about 49 years (lowest) while in Japan is about 83 years (highest).