Evolution and Radical Longevity

On the subway ride to work this morning, I finished a chapter of Jared Diamond’s The Third Chimpanzee, entitled “Why Do We Grow Old and Die?” In it, Diamond discusses how natural selection has played the prominent role in increasing our species longevity and also addresses why all systems, bodies or otherwise, break down over time. He focuses on the concept of “optimization,” that is, Nature’s tendency to maximize survival and reproductive success of the overall design, rather than optimizing particular elements.

To explain his point, he cites the Royal Navy’s decision, in World War I, to build a better warship by “keep[ing] the weight of the big guns nearly constant, and greatly increase[ing] the weight of the engines while still maintaining a total weight around 28,000 tons.” The result was the heavily armored, swift battle cruiser, a vessel which could outmaneuver the more clunky battleships. These battle cruisers were heavily publicized and celebrated as marvels of engineering. The ships, unfortunately, didn’t fare well in combat. To maintain the preferred weight, the designers had skimped on hull armor and anti-aircraft defense, making them easy to sink.

Diamond writes,

“In short, engineers can’t tinker with single parts in isolation from the rest of the machine, because each part costs money, space, and weight that might have gone into something else. Engineers instead have to ask what combination of parts will optimize a machine’s effectiveness. By the same reasoning, evolution can’t tinker with single traits in isolation from the rest of the animal, because every structure, enzyme, or piece of DNA consumes energy and space that might have gone into something else. Instead, natural selection favors that combination of traits that maximizes the animal’s reproductive output.”

And so it is with menopause, for example. Female hunter-gatherers were at great risk of death during childbirth. With each proceeding child, the risk increased. Those females who stopped being able to procreate later in life were therefore more likely to survive and mother the offspring already born to them, increasing the chances that their genes would be passed on. Menopause, Diamond contends, was a genetic mutation favored by natural selection, as is any advantageous mutation that increases our life spans without detriment to the rest of the corporeal vessel.

Because the body is the sum of its parts, then,

“there should not be just one, or even a few, dominant physiological mechanisms of aging. Instead, natural selection should act to match rates of aging in all physiological systems, with the result that aging involves innumerable simultaneous changes.”

In other words, at some point, “everything collapses at once” and we die. For this reason, Diamond argues that we can not find the fountain of youth by seeking to remedy one critical flaw in our design. The many tried methods of the previous century, be they injections with bee or snake venom, consumption of particular vitamins or foodstuffs, or any number of other outlandish “cures for aging,” are all pointless.

But what to make, then, of Aubrey de Grey, the Cambridge University geneticist (who can be immediately recognized by his impressive beard) and his claims that people who are now 60 years of age could live to be 1,000. Curiously, his arguments don’t disagree with Diamond’s assessment of the aging process. In fact, in this interview, his own discussion parallels arguments Diamond makes, particularly in regards to predation pressure dictating the opportunity cost of biological repair and, in turn, average life span of species. As Diamond explains, birds and turtles tend to live longer than similarly sized land mammals or shell-less reptiles because they have better escape ability (flight) or defense (shells) and therefore a better chance of surviving predation attempts. Because they are less vulnerable to attack and predation, then, the body can expend more energy on physiological repair. Diamond writes,

“If you’re likely to be eaten by a lion tomorrow, there’s no point in paying the dentist to start expensive orthodontic work on your teeth today. You’d do better to let your teeth rot and start having babies immediately. But if an animal’s risk of death from irreparable accidents is low, then there is potential payoff, in the form of increased life span, from putting energy into expensive repair mechanisms that retard aging.”

De Grey evidently agrees with Diamond regarding the evolution of aging, and his “cure for aging” doesn’t consist of “fixing” one broken mechanism; he suggests that a more holistic approach is necessary and, today, is feasible.

Despite making rational, informed arguments, though, I think De Grey is overly optimistic, especially with regard to the timeframe for such “improvements.” Yet the questions raised by the prospect of radical longevity should not be dismissed. It seems increasingly likely that our human lifespan will be lengthened, even if the marked jumps predicted by De Grey may come in the more distant future and involve less of a life span extension. Jamais Cascio, at WorldChanging, discusses such concerns in brief in his post on Charles C. Mann’s Atlantic Monthly article, “The Coming Death Shortage.” I have not read Mann’s piece, but Cascio responds to some of Mann’s concerns, most notably increasing social and economic inequality. Cascio disagrees with Mann’s “general disapproval of the idea of radical longevity,” pointing out that “too often we give insufficient credit to the resiliency of human culture.” While this last statement is certainly accurate, I believe there is much reason to be concerned, particularly when considering population and environmental impact, though I stop short of bemoaning the concept/possibility of radical longevity altogether.

I think the comment by Mr. Farlops, at the bottom of the Cascio piece, puts it well.

“Birth control and lack of sustainability are also problems now. Longevity only magnifies their importance. Perhaps some passive yet progressively minded people, faced with long life in a declining world, might be forced to do something about it. But we really can't count on that either. [...] I guess my opinion could summarized as let's deal with sustainability, birth control [...] now and not worry about stuff like rejuvenation and longevity.”

Indeed.