Theories
on Aging
Aging is a complex process which has a variety of
working parts. Medical scientists and biological researchers continue
to study aging in order to give humanity a more complete
understanding of the mechanisms by which it occurs, and they also try
to learn ways to slow down or even reverse some aspects of the aging
process.
There are three primary mechanisms that control how we
age: Genetic Aging, Biochemical Aging, and Physiological Aging.
Genetic
Aging
One of the
three mechanisms by which human beings age is genetic. There are many
forms of genetic aging, but all revolve around the idea that genetic
breakdown causes the body to age over time. As we grow older, the
genes become more prone to mutate. These mutations can cause a
variety of issues to occur, one of which is cancer.
If a gene
alters in a way that encourages endless replication, this
significantly increases mortality risk, for example. Genetic
mutations can also lead to other, less severe, genetic issues which
simply impede the body's ability to perform the functions necessary
to maintain a healthy and optimally functional body.
Small
formations on the ends of our genes known as Telomeres also have an
impact on aging. Telomeres are sections of junk genes at the end of
our chromosomes which keep the active genetic code intact. As we age,
these Telomeres become shorter and shorter, increasing the risk of
genetic malfunction and mutation.
Finally,
there are certain genes that only seem to express themselves later in
life or when certain negative pressures are applied. And these
negative pressures cause the aging process to occur more quickly.
Biochemical
Aging
Biochemical
Aging is a precursor of many forms of Physiological Aging.
Biochemical Aging refers to intracellular and extracellular processes
which contribute to aging in some way. In some cases, this is the
result of natural chemical processes which cause our body to slowly
break down over time, such as the inevitable oxidization which occurs
as a natural side-effect of the chemical processes which keep us
alive.
Other
symptoms of biological aging are the result of changes in the way
that our body functions, often for reasons that we are just beginning
to understand. The way that our bodies produce Human Growth Hormone
and Testosterone are good examples of this form of Biochemical Aging.
When we
are young, our bodies produce ample levels of these hormones, and it
encourages growth during adolescence and supports good health during
early adulthood. Around the age of thirty, however, these hormones
start to decline because the brain sends fewer and fewer signals for
them. Also, hormones which control stress are produced in lower
concentrations with age, which can increase the influence of
psychological and physiological stress, which can cause other issues
related to aging to become much more dangerous and severe.
Physiological
Aging
Physiological
aging refers to the physical changes that take place as a result of
aging. Our teeth represent one of the most noticeable markers of
physiological aging. Our teeth grow into place after our baby teeth
fall out when we are young. After your teeth fully develop, your body
has no mechanism to rebuild them and they slowly degrade over time,
at a rate dependent upon how well you take care of them.
Graying
hair is another type of physiological aging. Hair color is actually
produced by tiny cellular organs known as Melanocytes. The color of
your hair is dependent upon the type of pigment that these cells
create, as well as the quantity and concentration at which they are
produced. The more melanin that the Melanocytes produce, the darker
your hair will be.
People get
gray hair because the older that they get, the less pigment that
Melanocytes secrete over time. There are actually scientific studies
being performed regarding how to influence these cells to continue
producing pigment later in life, potentially allowing aging men and
women to naturally maintain their natural hair color.
Other
Physiological aging changes are more than cosmetic, however. There
are certain processes that occur regardless of how you take care of
yourself as you grow older. Your baseline blood pressure will slowly
go up over time, and your heart muscles will slowly harden, a
condition known as atherosclerosis. Many physiological signs of aging
can be alleviated with medication or a healthy lifestyle, but the
general trends will continue over time without particular forms of
treatment (many of which don't exist today).
How We
Age Does Not Explain Why We Age
These
three concepts, Physiological Aging, Biochemical Aging, and Genetic
Aging, only serve to explain the processes by which we age. These
processes do not answer the ultimate question of Why We Age, however.
There are a number of theories associated with answering the question
of why we age, but all of these theories belong to two distinct
classes: Program Theory and Error Theory.
Program
Theory assumes that aging occurs for evolutionary reasons, as a means
to improve the effective viability of the species. There are a number
of means by which this can be true, and it assumes that from the day
that we are born, we are designed to progress down a set path from
birth to death which maximizes the long term survival of the species.
These programmed theories can be considered like a series of stages
of life that eventually leads to death.
Error
Theory, on the other hand, assumes that we are not genetically
designed to self-destruct, but it is the result of a potential
multitude of malfunctions which slowly reduce the viability of an
organism until it eventually dies. There are a wide variety of forces
that pressure an organism to break down and reach the end of its
lifespan. It is incredibly important to note that the reality is
likely much messier than a single theory, and there are inevitably a
multitude of pressures which lead to aging, which are likely related
to hypotheses of both Program Theory and Error Theory.
Below is a
collection of some of the theories associated with Why We Age:
Program
Theories of Aging
Programmed
Senescence
This
theory behind aging centers around the idea that we are programmed to
age from a genetic level. It assumes that there are certain genes
that turn on at a certain stage of the lifespan which change the way
that our body works at a cellular level. This creates a cascade of
change which causes our bodies to slowly deteriorate over time.
There are
a number of cellular processes in the human body that involve
programmed cell death, which is also known as apoptosis. Advanced
theories regarding Programmed Senescence hypothesize that the genetic
code of all animal species induces aging as a form of organism-wide
apoptosis which makes way for the newer, younger generations.
Endocrine
Theory
This
Programmed Aging Theory hypothesizes that the endocrine system has
the ability to control the rate at which an organism ages based off
of both a natural biological clock as well as outside influences
which may induce or postpone aging. This theory is also known as the
Hormone Theory of Aging.
There are
many insects, for example, that have the ability to live much longer
lives if the conditions are not ideal for reproduction and
procreation. If it is excessively cold, there is not enough food, or
there are not enough partners, many insect species will release
hormones which halt or slow down aging until conditions are more ripe
to create offspring.
In human
beings and other mammals, Growth Hormone and Sex Hormone production
declines around midlife until the end of the lifespan. There is
powerful evidence that these hormones have a positive impact on
health and longevity, and there are those that argue that the body
reduces production of these Anti-Aging Hormones over time so that the
older generation can make way for the new generation.
Immunological
Theory
This aging
theory makes the hypothesis that immune systems weaken over time as a
result of evolutionary pressures to encourage the organism to
eventually become ill and die. This theory is also known as
Immunosenescence. When we are young we are incredibly resilient to
disease, but the older that we get, the less able our bodies are to
fend off illness.
There is
some evidence that an organism's ability to fight disease drops over
time without regard to external factors, which leads some to suggest
that this is an evolutionary strategy to encourage the young and
healthy to acquire dominance over time. This change isn't exclusively
the result of exterior factors, but as a result of changes which are
deeply embedded in our genetic code.
Error
Theories of Aging
Wear
and Tear
This
theory is quite straight forward. Our bodies grow and develop through
childhood and adolescence, but after our bodies reach a point of peak
performance, certain parts of our body start to age and decline in
function because they do not have the capacity to heal themselves or
have a limited ability to heal themselves.
One
example of wear and tear is the scarring deterioration of the skin.
When you receive a cut, your body has the ability to seal itself up
and maintain a closed system, but if scars don't heal properly they
will remain on the skin the rest of your life, because the body does
not have a means to make the marks associated with these old wounds
disappear once they are fully healed.
Another
example of wear and tear involves the liver. The liver is an organ
that has a limited ability to heal itself. Liver damage can result
from a number of different lifestyle choices, including alcoholism,
obesity, and drug abuse. The liver expends a lot of energy filtering
impurities out of the body, and if too much is consumed for too long,
the liver starts to become overwhelmed by fat tissue and cirrhosis.
Rate of
Living
This form
of aging is based on the hypothesis that, regardless of any
evolutionary benefit, animal organisms have a lifespan which is
highly correlated with their metabolism throughout their lives.
For
example, rabbits and other small animals with very fast heartbeats
tend to have very short lifespans. Animals like turtles, whales, and
elephants have slow metabolisms which are associated with very slow
heart beats, and they tend to have very long lifespans.
Although
metabolism does seem to play a certain correlative factor with regard
to the average lifespan of various species, it is not a hard rule,
and evidence suggests that it does not apply effectively to humans.
Low Metabolism in humans is associated with a shorter lifespan, and
is correlated with health issues such as obesity and cardiovascular
disease.
Crosslinking
Crosslinking
is a theory of aging that assumes that the older that we get, the
more links that the proteins in our body make, causing them to no
longer function as effectively. One example of crosslinking which
leads to physical aging is skin elasticity.
When we
are born, our skin is soft and returns to position quickly if pulled
or compressed. This is because the collagen in our skin is optimally
linked. The older that we get, the more crosslinkages that are made
among the collagen of our skin, which causes the skin to tighten and
become less optimized. These links eventually start to cause skin
cells to function ineffectively or even die off because the protein
links are so tight that nutrients are not delivered efficiently.
Crosslinking
is also one reason why the immune system loses its function over
time. The body loses its ability to successfully process glucose from
the blood. This causes blood sugar to increase which has a toxic
effect on the cardiovascular system. Sugars in the blood react with
protein, increasing the prevalence of free radicals which can do
major damage to the body over time.
Free
Radicals
Free
Radicals are the result of the very chemical processes of the human
body which sustain us. As our bodies react with oxygen to create
energy, they release spare atoms which travel haphazardly through the
body causing chemical reactions and reaction cascades that can do
harm to the body.
One of the
body's primary lines of defense against Free Radicals are nutrients
known as Antioxidants. The human body has the ability to produce some
forms of antioxidant naturally, but others must be consumed in the
diet. Omega-Three Fatty Acids, L-Carnitine, and Vitamin-C are some
examples of antioxidants.
Free
Radicals cause aging because the incremental damage caused by these
chemical reactions slowly degrades the body, causing organs and cells
to lose their ability to properly function and this slowly leads to
declining health and vastly increased mortality risk.
Error
Catastrophe
This form
of Error Theory is associated with the way that our bodies utilize
proteins. As a result of various other interferences, the cellular
organs which generate necessary proteins in our body can malfunction,
causing them to produce damaged proteins which can negatively impact
health and normal function.
One of the
most well-known forms of Error Catastrophe is actually Alzheimer's
Disease. Alzheimer's Disease is caused when our brains become
overloaded with prions, which are proteins which the body has folded
improperly. These prions have the ability to convert other healthy
proteins into the same form, spreading damage throughout the brain,
deteriorating normal function over time until eventually inevitably
leading to death.
Error
Catastrophe also refers to the point at which mutations in proteins
or genes reach a point at which the cell can no longer survive and
propagate under normal circumstances. Eventually, the organism dies
because cellular function breaks down at organ level and finally at a
universal level.
Somatic
Mutation
This form
of Error Theory is related to Error Catastrophe, but is explicitly
related to genetic function. A number of different factors can
eventually cause genetic function to alter, which causes aging and
eventually can lead to death.
Cancer is
often the result of Somatic Mutation. A gene can mutate, causing it
to reproduce indefinitely. This genetic mutation alters the healthy
function of the body, and over time, the cancer can spread to other
areas of the body and flood the entire organism with replicating
cancer cells, which will inevitably lead to death. Cancers can
usually be treated effectively if caught early, but if allowed to
spread, they often become almost universally lethal.
Somatic
Mutations can occur at any time from conception to the end of the
lifespan. Sometimes, these mutations lie dormant for many years,
perhaps even through the entire lifespan, but other times, they
eventually lead to cancer or other physiological malfunctions.
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