Anyway, our brains have been on the job for two millenia and the ultimate conclusion it has reached is that there is no reason or if you like purpose to life. — TheMadFool

Where are you getting that from?

I'm surprised no one has brought up Calhoun's rat utopia experiments.

The major improvements in longevity have come about through better agriculture (more and better food -- this goes back to the late 19th / early 20th Century. Civil engineering in the form of sewers and pure water systems also can take credit for longevity. The third thing that has made a large difference is public health measures such as vaccination programs. — Bitter Crank

"The average age" of people has always been kept low by infant and child mortality. — Bitter Crank

The average worldwide life expectancy has increased from 48 years in 1950 to 78 years in 2015.
While improvements in infant mortality account for a portion of this data there have also been a significant reduction in death rates as diseases have become increasingly treatable, working conditions have improved, and industrialization has increased the global standard of living. After reviewing some material on the points you brought up I would generally agree with the statements you made regarding agriculture and civil infrastructure so far as developing nations are concerned.

That said, notice that the global life expectancy has increased 30 years in the last six decades.

In 1950s America the average life span was in the 60s while nowadays the average lifespan for Americans is in the 70s and projected to increase. I would argue that advances in medical treatment would account for most of this extra decade.

World life expectancy figures

I remember learning a bit about ecology in college. There are factors that will limit the population growth, such as lack of food, lack of water, loss of habitat, predators, and diseases. Human populations will increase, but so will the mortality rate. — Purple Pond

Not in industrialized societies. Medicine is advancing rapidly and allowing consumers to live longer than ever. The main reason certain groups in industrialized societies reduce their average number of offspring is economic, not a lack of resources.

It is unrealistic to think that human beings will ever curb their desire to reproduce, regardless of the limited carrying capacity of our environment. Furthermore there are no natural predators to keep our population in check, meaning the only historically significant ways large scale population reductions could occur--and they will occur--are famine, war, and disease.

The idea that a future technology will prevent this kind of reality is ill-founded, though we may through technology extend the limits of what our environment can sustain (e.g. agriculture) we will still have a limited amount of space to exist in and our numbers will continue to increase. Technology cannot solve what is essentially a human problem.