Immortality Lessons from Animal Life
Everything around us ages. Everything made of iron will rust and corrode over time. From pipes and door hinges to supporting pillars, they all succumb to rust. The same holds true for our cars, which gradually wear out. Engine efficiency decreases, and as they age, cars break down more frequently. Even our smartphones, over time, become less responsive. The fact that aging is evident in all things around us leads us to think that the same aging process occurs within our bodies.
Intuitively, we often explain biological aging using analogies from inanimate objects. We liken all the symptoms and signs of old age to those of aging in non-living things. For instance, we analogize clogged arteries due to fat buildup to pipes clogged with deposits, brittle bones to decaying wooden furniture, or joint inflammation to reduced door hinge mobility due to rust. It’s as if there’s a universal law stating that all things must deteriorate or age, whether living or not.
But is this intuitive way of thinking correct?
Analogizing living organisms to inanimate objects is fundamentally flawed. From the standpoint of thermodynamics, inanimate objects tend to deteriorate with age. The second law of thermodynamics states that entropy always increases with time. Order in the universe can only move in one direction — toward chaos, symbolized by increasing entropy. This can explain why non-living objects become worn out. It’s due to the increasing disorder within them. You can’t defy the increase in entropy. Entropy in a system can only be reduced if there’s an external input of energy. Energy input is needed to counteract wear and tear.
A car, for example, is not a living entity capable of using external energy to self-repair. Our bodies can do that. Unlike a car, which is a closed system, a biological body is an open system, meaning it continually receives energy input from the outside that can be used for self-repair. Similarly, a door hinge cannot absorb energy from the outside through photosynthesis or by devouring other hinges or spoons and digesting them to generate energy for self-repair. Biological cells can. They can digest food, harvest energy in the form of chemical bonds, and use it to repair damaged organelles.
From the explanations above, it’s clear that analogizing biological aging with the aging of inanimate objects is incorrect. If the basic premise is flawed, so is the conclusion that all living beings age.
But can it be that there are living beings out there that do not age? Indeed, there are.
Before we delve further, let’s first discuss what aging is. To this day, no one knows exactly what changes can be called a representation of the aging process. Is it wrinkled skin? White hair? Brittle bones? Creaking joints? What is clear, regardless of the symptoms and signs, is that the aging process can be defined as an increasing probability of death. The older your chronological age, the higher your probability of dying. Suppose your chance of dying is only 1 in 1000 at the age of 20. In that case, it increases to 1 in 500 at the age of 40, then to 1 in 250 at the age of 60, and so on. This probability of death can be statistically calculated using mortality tables specific to a particular population and is usually done by statisticians at an insurance company.
So, if we encounter a population consisting of individuals whose probability of death increases with age, we can say that this population experiences aging.
Do all living beings out there show the same increasing pattern? The answer is No.
There are some living beings that do not show an increasing probability of death with age. Their likelihood of dying remains constant as they age. Generally, such creatures die due to predation or disease. Their chances of dying from being preyed upon or falling ill tend to stay constant throughout their lives. Aging may indeed occur in these living beings, but before aging takes its toll, they’ve already died at the hands of other living creatures. Many creatures have this fate in their natural habitats. Aging becomes apparent when they are protected from predation and disease, such as animals kept in a zoo. They can live longer than the average age if they remain in their natural habitat. These animals ultimately age and die. Their probability of death curve becomes identical to that of humans.
However, there’s a type of living being with a unique aging pattern. They either do not age at all or seem to undergo a reverse aging process. As they get older, rather than experiencing an increase, their probability of death decreases. In other words, the older they get, the healthier they become, and their chances of dying decrease! It’s much like the movie The Curious Case of Benjamin Button.
No one knows for sure when these living beings will die, except from illness or disaster. Some of them live up to 300 years, and the oldest can reach 80,000 years. These include Galapagos tortoises, lobsters, greenland sharks and Bristlecone Pine trees. Not only do they become healthier with age, but their fertility also increases. Lobsters become more fertile as they age. It’s truly counterintuitive. The oldest lobster ever caught in 2009 was estimated to be around 140 years old and weighed over 20 kg. It died from disease, not from aging. The Greenland shark (Somniosus microcephalus) is another fascinating example of long-lived creatures. To date, this shark stands as the world’s oldest known vertebrate. Recent studies have revealed that their age can reach a staggering minimum of 272 years!
What’s even more intriguing is that laboratory analyses of Greenland Shark tissues do not indicate that they possess significantly superior free radical-fighting abilities compared to shorter-lived creatures. Just so you know, free radicals are highly reactive molecules that can wreak havoc on various structures within cells. Free radicals typically stem from the byproducts of energy metabolism, akin to the emissions from motor vehicles. Given that body size is inversely proportional to the rate of energy metabolism within their tissues, one might expect larger-bodied organisms to have longer lifespans.
In theory, this can be explained as follows: the lower the rate of energy metabolism in a tissue, the fewer free radicals it generates, and therefore, the less damage it accumulates over time. Consequently, larger-bodied creatures should produce fewer destructive free radicals than their smaller counterparts. However, this pattern doesn’t seem to hold true for Greenland sharks and some other species, such as naked mole rats. Despite having a body size relatively similar to rats, naked mole rats do not share the same lifespan. Naked mole rats can live significantly longer than rats.It appears that aging isn’t an inevitable and rigid process, but rather a malleable one that can be tailored as needed. Biological systems can either lengthen or shorten aging process depending on the natural selection pressures in the environment where the organism resides.
There are many factors at play that determine the longevity of a creature. Exploring such factors through studies can provide us with insights into the nature of the aging process, how it occurs, and what we can do to modify it. The fruit of the tree of life seems to be hidden somewhere, waiting to be unveiled.
