We live longer than our ancestors thanks to our greater wealth and more advanced technology: risk of death is reduced at all ages, the level of damage suffered due to infectious disease and other causes is lowered throughout life, and inroads made into means of alleviating age-related disease. When it comes to effects across a life span, however, our extended lives are so far largely incidental, a side effect of improvements in medicine and quality of life that were introduced to satisfy other, more short-term goals.
This shows that aging and life span is very plastic - it can be changed, and is very readily changed. On the other hand, it tells us next to nothing about what lies ahead, as the rejuvenation biotechnology of the future will be an entirely different beast from the medicine of the past. Only now is the research community deliberately trying to manipulate the processes of aging, or repair the biological damage that causes degeneration. Given this shift in what is possible, projecting past trends to the future is unwise: the deliberately engineered changes in longevity of tomorrow will not look like the incidental benefits that slowed aging yesterday.
Here is an article on recent research that seeks to quantify the degree of improvement in human life expectancy that has occurred in recent centuries - you might want to look at the paper itself since it is open access.
It's said that life is short. But people living in developed countries typically survive more than twice as long as their hunter-gatherer ancestors did, making 72 the new 30, according to new research. Most of the decline in early mortality has occurred in the past century, or four generations, a finding that calls into question traditional theories about aging.
But there's a larger message from the research: Our estimates about the limits of human lifespans may be too low. The study findings "make it seem unlikely that there is a looming wall of death ... which kills off individuals at a certain age" because of genetic mutations that build up as we age.
For example, hunter-gatherer humans were about 100 times more likely to die before age 15 than today's residents of Japan and Sweden. And the study says hunter-gatherers were as likely to die at age 30 as Japanese people are at age 72. But the human lifespan didn't grow gradually over thousands of years. The big jump occurred after 1900 in what the study authors call a "rapid revolutionary leap."
In the big picture, the research challenges the idea that genetic mutations over a lifetime prevent humans from living very long ... Without changing our genetic code at all, we have all of this improvement in mortality at these ages where these mutations should kill us off. And we got all this improvement without 'fixing' any of these mutations that are predicted to cause our bodies to break down in various ways.