Posted on | October 18, 2012 | 2 Comments
If you were a Swede born in 1800, you would likely have viewed the world as a hostile place and human life as fragile and short lived. That was because life expectancy for Swedes was only 32 years, roughly where it had been for hunter-gatherers for many thousands of years. But by 1900, life expectancy had increased to 52 years, and by 2000 topped 82 years. In attempting to answer the question “Why the dramatic advances over the past 200 years?”, Oscar Burger and his colleagues at the Max Planck Institute for Demographic Research have set off a policy debate just as the presidential campaign enters its final weeks.(1)
Dr. Burger believes that the only rational explanation for the sudden advances in human lifespan are changes in our environment rather than biologic evolution and adaptation. “I still can’t believe how recent most of the progress is…….. it seems unlikely that there is a looming wall of death … which kills off individuals at a certain age”.(2) What he is referring to is the widely held believe that human organisms genetic equipment deteriorates with age due to mutations assuring our early demise. Of course, that also implies that genetic engineering could solve the problem, and greatly change the human horizon.
Burger isn’t buying it. “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.”(2)
To explain human success especially in the past 100 years, Burger’s research points to the rapidly improving environment. “Certainly clean water, better shelter, food and medicine all make a difference”, he says.(2) We humans now have catalogued over 8000 generations, each time handing off our genetic blueprint to our offspring. And yet, our lifespan progress has not been gradual and deliberate. Rather it has been shockingly steep and recent, witnessing amazing generational gains at every stage – birth, adolescence and adulthood.
Of course, such an assertion places a spotlight on a range of biologic research. Thousands of scientists have been laboring for decades on techniques that manipulate the biology of aging. By adjusting genetic make-up, they have extended selective mice lifespan by 50%, fruit flies by 85% and worms by 100%. Other animals have survived longer, if not happier lives through near starvation diets which supposedly trigger life inducing changes in one’s chemical and endocrine milieu.(2,3,4)
The environmental argument for extended longevity cuts both ways. For example, how will the worldwide obesity epidemic and ozone depleting, fossil fuel induced global warming impact our human future? No one is making predictions. Burger says, “In terms of what’s going on in the next four generations, I want to be very clear that I don’t make any forecasts. We’re in a period of transition and we don’t know what the new stable point will be.”(4)
University of Chicago public health professor S. Jay Olshansky believes the authors “have a particular bias toward reporting only news that favors a preconceived notion that life expectancy can only rise.” And U. C. Berkeley’s Ronald Lee, director of the Center on Economics and Demography of Aging says ”we still do not know the limits, if any, to the improvements in human longevity that have been occurring rapidly and steadily over the past two centuries”.(3)
The bottom line is this, we left chimpanzees behind in the evolutionary dust some 6.6 million years ago. We limped along, not faring very well, for all but the last 200 years. In the past century, a moment in time spanning just 4 of our historic 8000 plus human generations, we took off. This period coincided with rapid scientific and technologic advances, cleaner air and water, greater nutritional support, improved education and housing, expanded public health related governmental policy, and establishment of a safety net for our most vulnerable citizens.
What of the health future? At least for the U.S., considering the very different policy approaches of our presidential candidates, we will be determining that in part on November 6, 2012. Vote!
For Health Commentary, I’m Mike Magee.
1. Burger, O., Baudisch, A., Vaupel, J. W. Human Mortality Improvement in Evolutionary Context. Proceedings of The National Academy of Scientists (October 15, 2012). http://www.pnas.org/content/early/2012/10/10/1215627109.abstract
2. Dotinga R. Big Rapid Gains Made In Human Lifespan. HealthDay. October 15, 2012. http://consumer.healthday.com/Article.asp?AID=669648
3. Healy M. Modern Humans Found To Be Fittest Ever By Survival, By Far. LA Times. October 15, 2012 http://www.latimes.com/news/science/la-sci-aging-biology-20121016,0,2921588.story
4. Stokes T. Life Span of Humans Took A Huge Jump In The Last Century. October 15, 2012. http://www.msnbc.msn.com/id/49423829/ns/technology_and_science-science/#.UIBBfaDC6xI