I’m sorry that this blog entry is a bit late, I arrived in Miami yesterday and have been scuba diving all today (as guessed, I’m not very good at scubaing, if that’s even a word because that just looks wrong).
Today I’ll be discussing the essential epidemiological idea of resistance vs. tolerance. Resistance is the ability of an organism to avoid being invaded by a pathogen or effected by an external stimulus. Tolerance is the varying degree of aptitude an organism has to endure an infection and persist. These two topics are not always mutually exclusive (Mauricio et al., 1997) and organisms can employ both techniques in order to increase their overall fitness. To get a better understanding of these two topics let’s use some examples.
Everyone should know the basic plot of the Lord of the Rings trilogy, there is a ring which has magical powers which renders the user the ability to tap into magic (invisibility, telepathy, and the decrease of aging). However, there is a dark side to this ‘simple’ piece of jewelry which influences the wearer via ‘dark magic’. It can alter the personality, aggressiveness and decision making of the bearer causing devastating psychological and physical conditions, and even death. Throughout the series (and other extended universes) Tolkien makes it clear that some individuals are more susceptible to the ring’s dark forces and powers of suggestions than others.
For example: Bilbo Baggins, Frodo Baggins, Sméagol, and Samwise Gamgee (all hobbits (or at least sort of hobbits), suggesting perhaps a species specific increased tolerance) all were able to be ring bearers (for varying amounts of time) without suffering intense negative repercussions (when comparing their experiences to other holders at least). This means that these hobbits have higher than normal tolerance for the ring’s infectivity and can keep the negative effects at bay better than other individuals.
Boromir, Galadriel, and even Gandalf all had extremely decreased tolerance for the ring’s power (most likely due to life history traits such as: level of power and ambitiousness) and if allowed to keep the ring, they would have suffered from decreased fitness and ultimately mortality.
This is a simplistic system to examine as no individual (apart from Tom Bombadil perhaps) can be resistant to the powers of the ring and thus varying levels of tolerance solely influences the structure of the community. However, there are ecosystems that have individuals with varying degrees of resistance, tolerance and a mixture of both which makes this concept even more difficult to understand. In order to breed a resistant species in the LOTR universe you would have to closely monitor many different things. The length to which each bearer would have the ring would have to remain short (the longer you have the ring the more it affects you it seems) and the bearer would have to be part of the hobbit species (they are more tolerant due to their individual and species histories). Does the dilution of pathogen burden sound familiar as a strategy for species resistance? Check out the previous blog entry if not.
Since the ring was destroyed in Mordor it provided all the different species in the Middle Earth ecosystem with increased resistance to the power of dark magic. However perhaps the ‘Sauron pathogen’ much like smallpox may not be eradicated from the population for good.