It has been stated that in the 1800s, there was not a single country that had a life expectancy of even 40 years old, but that statistic, is somewhat deceptive, mainly because the prevailing reason why life expectancy was so abysmally low was because the old, the infirm, and especially the very young, were susceptible to infectious diseases such as tuberculosis, dysentery, and pneumonia, that were often fatal to the very weak and vulnerable. In addition, this reduced lifespan existed before the widespread use of antibiotics and vaccinations, as well as the clear understanding of the importance of good sanitation as well as good and abundant drinking water. Once all of these things came into play, then the very young, in particularly, infants, were able to survive their childhood and subsequently as reported by gcanyon.wordpress.com, we read that "Comparing just life expectancy for 20 year-olds, in 1850 a young man could expect to live to 60.1. In 2004, that same man could expect to live to 76.7."
Clearly, this would indicate that life expectancy since 1850, though improving a good amount, has not despite the expenditure of billions upon billions of dollars on healthcare, medicine, pharmaceuticals, doctors, technology, robotics, and hospitals, improved all that much. This seems to imply that the great lifespan improvement breakthroughs actually came to humanity, one hundred years ago, or even longer than that, and that improvement came down to fundamentally understanding the nature of infectious diseases and thereby creating the immunizations and vaccinations to bolster and defend a given body against such.
The fact that life expectancy has increased further in recent generations is more a reflection of better hygiene, plentiful food, and significantly better natal care for newborns and infants. So that, according to infoplease.com, the average life expectancy in America of those born in 1950 was 68.2 years, and for those born in 2010, it has gone up to 78.7 years, which is an improvement of just over 15%. While that might even sound pretty darn good to a lot of people; taking into consideration all of the medical breakthroughs and pharmaceutical drugs that have been added and manufactured since then, the reality is, that improvement is rather disappointing.
The bottom line is that the biggest reason why life expectancy has increased really comes down mainly or almost exclusively to the very significant reduction of infant mortality, and there really aren't any other significant reasons why adult lives have added years onto their life expectancy, other than the implementation of a good diet, antibiotics and vaccinations, good sanitation, clean drinking water, general prosperity, and preventative healthcare.
The challenge for modern day medicine is to do better than they have done to date in helping to provide for more people a longer life expectancy, in addition to that longer life expectancy being of good quality health. Currently, no country spends more money per capita on healthcare than the United States, yet, on a life expectancy chart as shown by infoplease.com, the United States ranks 43rd in life expectancy. This would strongly imply that whereas there was a time when the United States was a true pioneer and meaningful innovator in medicine that eradicated vicious infectious diseases, and drastically improved the life expectancy of infants; that those impactful days are gone, and further life expectancy improvements appear to be rather modest, at best.