(Editor’s Note: Willow Yang is a frequent letter-writer/contributor to the Post-Geek Singularity and the Robservations live-stream. Her commentary on STAR TREK: THE ORIGINAL SERIES episodes have become a fan favorite. As a result, we’ve decided to publish them as part of our TREK TALK series under the title: “Willow Talk”.)
I’m coming up towards the end of my science conference in Boston. In the spirit of the event, I’d like to discuss the causes of aging and immortality, with reference to the Star Trek episodes Miri, The Apple, and The Deadly Years.
Aging is a complicated process that is caused by a host of different factors, many of which are still poorly understood. I will only touch superficially on the molecular side. The DNA damage theory of aging proposes that the degeneracy we experience as we grow older is in part due to the accumulation of mutations in our DNA. This is caused by both external, environmental factors such as radiation, toxins, and pathogens, as well as inherent errors in our cellular replication machinery. The longer we live, the more mutations we accumulate in our DNA, the more dysfunctional our cells become, which manifests itself in the host of negative effects that we experience in old age, including an increase in the risk of cancer. In addition to mutations, we also have the issue of our chromosomes shortening. As a quick aside, for those who aren’t familiar with the subject, we carry an enormous amount of DNA that must be condensed in order to be able to fit inside our cells. To achieve this, our DNA is wound tightly around special proteins, known as “histones”, to form small, tidy packages called “chromosomes”. Human cells typically carry two copies of 23 chromosomes, which collectively form our “genome”.
Without going into details, during cell replication, DNA polymerase, the enzyme that’s responsible for duplicating the genome, is unable to synthesize the last segments of our chromosomes. As a consequence, every time our cells divide, our chromosomes get shortened. Now, this would obviously be problematic if we lose DNA that encode any functional proteins. Fortunately, we have evolved to circumvent this problem by acquiring long strands of repeating DNA elements called “telomeres” at the ends of our chromosomes. These elements do not encode for anything, but are present solely for the purpose of buffering against the loss of coding DNA during each round of replication. After each cell division, our telomeres get eroded so that eventually, after enough rounds of replication, we will lose them entirely and will no longer be able to prevent the loss of important coding regions of our chromosomes. Thus, our cells have a finite number of turnovers, known as the Hayflick Limit, after which cell divisions will cease and the old cells will die without producing new replacements. Since the discovery of this phenomenon, people have touted the possibility of extending telomeres as an anti-aging method. This is a bit misleading however, because, with the exception of those suffering from diseases that result in shortened telomeres, humans don’t typically die from telomere loss. Rather, we’re more susceptible to oxidative stress and other environmental mutagens, which will likely age and kill us long before our telomeres have actually run out.
In the episode Miri, we encounter a planet where an engineered virus has nearly arrested aging in the population of children (while apparently accelerating aging in adults and causing them to die). The only vague explanation that was provided for this phenomenon is that the children exhibit a reduced production of nucleic acids. Since cells do have a limited number of turnovers, it might seem reasonable to try slowing down DNA replication and cell division in order to slow the aging process. However, this is actually problematic because the synthesis of nucleic acids is also critical for cells to manufacture macromolecules and perform functions that are necessary to sustain life. Moreover, cells are susceptible to wear and tear; they need to replicate and create new replacements or the body will rapidly degenerate. Finally, the children don’t appear to be protected from environmental mutagens, and will thus still sustain DNA damage from UV light, free radicals, pathogens, and other harmful agents.
In the episode The Apple, we are introduced to a utopian society of natives who worship a mysterious machine that, in addition to providing them with safety and food, enables them to live thousands of years without aging. Assuming that the natives have a biology that’s relatively similar to ours, they will experience the same DNA aging processes that we do. Since the machine is able to shield them from harmful radiation, toxins, and pathogens, it is reasonable that damage to their DNA will be minimized, allowing them to have an extended average lifespan. However, the machine will also need to be capable of detecting and carrying out genetic engineering, including the lengthening of telomeres and the repair of mutations caused by inherent errors in the cellular replication machinery, in order to halt aging altogether. Even in the most pristine environments a human, or anything biologically similar to a human, cannot survive beyond the limitations that are set by their molecular clock.
In The Deadly Years, the crew are exposed to a mysterious radiation that causes them to rapidly age. There is a small grain of truth to this: radiation damages DNA, and prolonged exposure to X-rays and UV rays are known to accelerate aging. Radiation also causes a host of additional problems that I don’t need to go into seeing that Chernobyl is currently on HBO. I probably don’t need to tell anyone that adrenaline does not offer protection from nor reverse the effects of radiation sickness either; that is just absurd. Furthermore, even if the radiation can be neutralized, it will not reverse the damage that has already been done to the cells. Similar to the aforementioned situation in The Apple, some extensive molecular engineering must be carried out to repair all of the DNA and other cellular structures that have been destroyed. Kirk and company de-aging instantaneously back to where they were prior to the radiation exposure? That is about as realistic as Kirk being brought back from the dead by an injection of Khan’s blood. Fortunately, I’m not one who care too much about scientific accuracy in entertainment.