Why we age

Marquette Magazine posed this question to a philosopher and a scientist.

The expert: Dr. Sandra Hunter, associate professor of exercise science, who researches age and sex differences in neuromuscular function, fatigue and exercise.

“None of us are spared from physical aging. It is the process that leads to a loss of adaptability and function and eventually death. So why do we physically age? More succinctly, why does our hair become gray, our muscles grow weak and our memory fail?

“Ultimately, the answer to these questions involves cell death that eventually leads to systems malfunctioning and whole body death. For example, our hair grays because the pigment cells in our hair follicles that release the pigment melanin gradually die. The pigment becomes more transparent, taking on a gray or white color as the hair grows. Similarly, the death of muscle fibers contributes to losing limb strength up to about 10 percent per decade after 50 years. The nerves (neurons) connected to muscle fibers can also die, as do neurons in the brain. Consequently, the human brain shrinks at about 2 to 3 percent per decade, starting as early as 30 to 40 years, so that a 10 to 11 percent loss of brain matter can occur by 80 years of age. Because neuron death in the brain is initially selective to the memory and planning centers, we tend to lose short-term memory and higher-level cognitive functions with advanced aging.

“There are many theories to explain physical aging, with most theorists agreeing that a range of theories work in tandem, some highlighted here. Genetic theories, for example, propose that aging is preprogrammed by our genes so that our genetic encoding is responsible for up to approximately 30 percent of our lifespan. Damage theories, on the other hand, propose that chemical reactions in the body eventually produce irreversible defects in our molecules. For example, damage can be caused to human cells by oxygen free radicals that are products of oxygen metabolism (a key method by which a cell gains energy). Calorie restriction may minimize free radical reactions and thereby increase life span, and it may also inhibit development of some forms of cancer and enhance the immune system. It has also been suggested that antioxidant vitamins (such as vitamins C and E) attack and destroy the free radicals, although there is no clear evidence to support their role in humans.

“What can we do to slow the aging process? Because physical aging can be accelerated by environmental factors such as lack of physical activity, regular exercise can offset physical aging and improve quality of life. The benefits from exercise, however, are in part genetically determined! Consequently, individuals physically age at different rates, which accounts for variance in longevity and quality of life because of both genetic and environmental factors. So regardless of where we are in the aging process it is inevitable and relevant to us all. The quest for the legendary ‘fountain of youth’ continues.”

How would a philosopher answer this question? Read the reply of Dr. Susanne Foster, associate professor of philosophy.