The Evolution of Death: Why We Are Living Longer

Afterword

Afterword The constant effort to dispel this darkness, even if it fail of success, invigorates and improves the thinking faculty. —Thomas Malthus, Essay on the Principle of Population We love machine-gun massacres in movies, but death from old age seems somehow unnatural and horrifying. —David Lovibond, “No Way to Grieve” If we are to conceive Man as separate from nature, then Man does not exist. This recognition is precisely the death of Man. —Michael Hardt and Antonio Negri, Empire In the preface, you may remember, I suggested that science is like a whodunit, a detective story where a crime is uncovered and a mystery is solved. As things turned out, the evolution of death is not the crime I thought it was. Rather than a corrosive force shortening life, death’s evolution turned out to be a salubrious force lengthening life! It seems that our life span has lengthened, because our own intrusions in our environment (such as improved sanitation, nutrition, and medicine) have made our niche more wholesome than it ever was before, and, as it turns out, the very things that shape our longevity are the very things that select individuals for delayed death. Instead of dying while still near our peak, we are living longer than ever before. Increasingly, selection is choosing individuals with a greater potential for life. Consequently, our species is in the process of optimizing death! In other words, death is becoming more efficient and less costly. Death, it would seem, does not turn us into corpses as quickly as it once did, but the mechanism for death’s delay remains a subject of speculation. My guess is that death’s evolution is dominated by neoteny—the emergence of sexual maturity in juvenile morphs coupled to a tendency toward slower anatomical development—and we are living longer because our juvenile robustness is preserved later into adulthood. If, as I suggest, parsing germ cells into compartments of somatic stem cells and their cognates has expanded our stem-cell reserves, our sources of cellular renewal would be maintained at 151 youthful levels well into adult life, and our youthful vigor would be preserved well into our mature years. We might, thus, delay reaching the time our cellular resources are disabled, inadequate or exhausted and, hence, put off meeting our death. But here the plot thickens, and The Evolution of Death poses two new mysteries. First, why has death’s evolution escaped notice by gerontologists? Second, where is death’s evolution presently heading? What will happen to us if death’s evolution continues at its present pace or even accelerates? I won’t pretend to solve these mysteries, but let me begin this afterword with a critique of gerontology and proceed to project some possibilities for humanity in the future. HOW DEATH’S EVOLUTION ESCAPED THE GERONTOLOGIST’S NOTICE THE GAINS Gerontologists seem widely in agreement that human beings are living longer, which is to say that our median age at death is greater now than ever before. But many gerontologists still cling to the notion that we die after a definitive human life span and life’s ultimate boundary has not changed. The alternative notion that our life span can change and our death can evolve seems unacceptable if not loathsome to these gerontologists. Their problem is a commitment to aging genes. Frankly, I can sympathize with many gerontologists mired in biology’s prevailing gene paradigm. Nothing has prepared them to think about the prolongation of longevity, no less the evolution of death in epigenetic terms. I am, however, much less sympathetic with close-minded gerontologists who hound and abuse those struggling to understand longevity in new terms, notably the bio-gerontologist Aubrey de Grey. Alternatives to genetics, such as the epigenetic roles of mitochondria, DNA methylation, the reshaping of chromatin, and changes wrought by transposons and other “junk” DNA must be examined before we can claim to understand the inheritance of aging and the evolution of death. The notion that human beings are allotted three- or fourscore and ten years has ancient roots that remain stout today even if they are now proving to be of clay. Notwithstanding biblical claims for Methuselah and his kin’s extraordinary longevity, The Booke of Psalmes tells us that old age arrives at threescore and ten years and we’re lucky to survive fourscore years and ten.1 This conception of our lifetime was not only endorsed during the Renaissance2 but reinforced throughout the Enlightenment. As the political...