The military forces of the United States are not to be deployed within the country.  Many people think it’s a clause in the Constitution, but actually it was an afterthought, enacted into law in 1807, strengthened and clarified by the Posse Comitatus Act of 1878.

The Founding Fathers reasoned that government is always in danger of assuming imperial powers, escaping from democratic control.  If ever our government were to turn against the people and treat them like a domestic enemy, they would not start from the ground floor to assemble an occupying force; rather they would be tempted to use the existing military forces, the standing army, grotesquely turned against the American people whom they were sworn to defend and protect.

Evolution as conceived by Charles Darwin has no forethought and no central direction, but often the results of natural selection are elegant and economical, as though they had been planned.  If evolution found it necessary to regulate the individual’s life span for the larger good of the community or the ecosystem, there would be no need to invent a new and specialized death program.  It would be far easier to coopt the body’s existing armies, and redirect them in a suicide mission.

The science of aging in the last twenty years has made one discovery after another of the body’s protective armies turned inward, repurposed to destroy the self.  In each case, researchers specialized in one particular disease notice that the body is attacking itself; they imagine that this is a unique case of “something gone awry”, and they write about “dysregulation” of this system or that system.  But when generalists in gerontology step back and see many examples of the same pattern, they suspect an evolutionary purpose.  In the same sense that the purpose of our eyes is to gather visual information and the purpose of our kidneys is to filter waste from our blood, we may say that aging has an evolutionary purpose, and that purpose is to eliminate the individual for the larger good of the community. All for one and one for all — only the “one” in this case is not the individual animal but the whole population, which if it grows too fast can crash the ecosystem on which all depend.

Arthritis.  The old view of arthritis was that the cartilage that cushions and lubricates our joints wears away with years of use.  Now it is recognized that osteo-arthritis has the same roots as rheumatoid arthritis.  It is an auto-immune disorder, the body’s immune system turned traitor against our bones and cartilage.

Atherosclerosis.  The old view of coronary heart disease was that over many years, cholesterol deposits on the artery walls in the same way that mineral deposits build up inside a water pipe and gradually come to clog the pipe completely.  Now it is recognized that inflammation plays an essential role.  When we are injured, inflammation is the body’s first line of defense against invading microbes; but in old age inflammation attacks healthy tissues, and the delicate linings of our arteries are among the most vulnerable.  Inflamed pieces of the artery walls break off, clog the artery and cause heart attacks.

Cancer.  The old view was that there are random mutations in a particular cell line, a series of unfortunate accidents that cause the cells to disregard regulating signals from the body and just continue replicating and growing out of control.  Now we realize that cancer is a failure of the body’s immune defense system.  When we are young, our white blood cells search and destroy incipient cancers, but as we get older the immune early warning system is gradually shut down.  The thymus gland, where these white cells are trained for their task, gradually atrophies with age.  And the cancer mutations themselves are not steady and random, but are ramped up as we get older by chronic, systemic inflammation.  Further, the deadliness of cancer comes not from the selfishness of uncontrolled growth, but from malicious “oncogenes” that create toxins, poisoning the body from the inside out.

Alzheimer’s Disease.  This is the latest paradigm to shift, highlighted in an article this week in the MIT Technology Review about the work of Harvard Med School Professor Beth Stevens.  The old view was that plaques and tangles accumulate in the brain from cellular waste products.  Now we are beginning to see that glial cells are the culprits.  When we are infants, the brain is sculpted by subtraction.  It is the glial cells that decide which nerve connections to keep and which to prune.  But in old age, this article reports, the cells “go rogue” and begin—unexplainably—to destroy nerve connections that are healthy, even essential for the brain’s function.  Could it be that this, too, is not a random dysfunctional behavior, but part of evolution’s program to reliably fix our life spans?

Evolutionary biologists have been the last to recognize this paradigm shift in our understanding of aging.  Since the 1960s, they have been committed to the idea that natural selection cares only about the individual, never the community.  This is the theory of the Selfish Gene.  But a growing wing of academic scientists has been gathering evidence that natural selection works both on individuals and on groups.  The new view is that evolution occurs simultaneously on multiple levels, so that both selfish and cooperative behaviors appear.  Communities and entire ecosystems may evolve in a way that is integrated for the good of the whole.  Only in this context can we make sense of the body’s civil insurrection that is aging.  We die individually as part of nature’s regulation of the ecological community.