Understanding Life Expectancy
The American Scientist is running a great piece on the measurement of life expectancy, and how the modeling of life expectancy overlaps with progress in the science of aging: "The systems-based explanation argues that complex machinery fails because many things go wrong. According to this model, as with your Toyota, so too with your body: The force-of-mortality curves for automobiles (called failure-rate curves) complied by demographers [bear] an uncanny resemblance to their human counterparts. Both human and automobile curves show an exponential increase in the force of mortality that tapers off in later years ... Surprisingly, mortality in the early years is eerily similar in people and automobiles: Defects in manufacture (machines) or development (organisms) reveal themselves early on. ... Such systems, whether we speak of Toyotas or biologists, are characterized by redundancy brought about by engineering (in the first case) or evolution (in the second). But, as University of Chicago gerontologists Leonid Gavrilov and Natalia Gavrilova have argued in their influential book The Biology of Life Span: A Quantitative Approach, the very redundancy that permits complex systems to endure a constant rain of light damage also allows such damage to accumulate, resulting in aging and eventual failure."
Link: http://www.americanscientist.org/template/AssetDetail/assetid/55855?&print=yes