Why do we age?

Gray hair, memory loss, wrinkles and brittle bones, sooner or later, each of us gets old (if we’re lucky). Yet scientists tell us that there is no evolutionary reason for us to age. So, why do we?

Effects of ageing

A number of characteristic ageing symptoms are experienced by a majority or by a significant proportion of humans during their lifetimes.

• Teenagers lose the young child's ability to hear high-frequency sounds above 20 kHz.
• A continuous decline in several cognitive processes occurs after a peak performance in the mid-20s age group.
• By age 30, wrinkles develop mainly due to photoageing, particularly affecting sun-exposed areas (face, hands) of fair-skinned individuals.
• Around age 35, female fertility declines sharply.
• In the mid-forties, presbyopia generally becomes apparent.
• Around age 50, hair turns grey in Caucasoids. Many men are affected by balding, and women enter menopause.
• In the 60–64 age cohort, osteoarthritis rises to 53%. Only 20% however report disabling osteoarthritis at this age.
• In the 70–79 age range, partial hearing loss affecting communication rises to 65%, predominantly among low-income males.
• Over the age of 85, thirst perception decreases, such that 41% of the elderly drink insufficiently. Frailty, defined as loss of muscle mass and mobility, affects 25% of those over 85.