Decline and fall (i)
All mammals age; the only animals that don’t age are some of the more primitive ones: sharks, alligators, Galapagos tortoises. There are different theories as to why humans age at the rate they do: aging is genetically controlled (maladapted individuals die out and well-adapted ones persevere); the rate of aging within each species has developed for the good of each species; an entropy-producing agent disrupts cells; smaller mammals tend to have high metabolic rates and die at an earlier age than larger mammals do; specific endocrine or immune systems are particularly vulnerable and accelerate dysfunction for the whole organism; errors in DNA transcription lead to genetic errors that accelerate death. All of these theories are disputed: no one knows why we age.
Schopenhauer said, ‘Just as we know our walking to be only a constantly prevented falling, so is the life or our body only a constantly prevented dying, an ever-deferred death.’ (Dad: ‘Why would a supposedly wise man want to think this way?’)
‘As we get older,’ the British poet Henry Reed helpfully observed, ‘we do not get any younger.’
On average, infants sleep 20 hours a day, 1-year-olds sleep 13 hours a day, teenagers sleep 9 hours, 40-year-olds sleep 7 hours, 50-year-olds sleep 6 hours, and people 65 and older sleep 5 hours. As you get older, you spend more time lying awake at night and, once asleep, you’re much more easily aroused. The production of melatonin, which regulates the sleep cycle, reduces with age – one of the reasons why older people experience more insomnia. By age 65, an unbroken night of sleep is rare; 20 percent of the night consists of lying awake. As I constantly have to remind my now light-sleeping father, people ages 73 to 92 awake, on average, 21 times a night owing to disordered breathing.
An infant breathes 40 to 60 times a minute; a 5-year-old, 24 tot 26 times; an adolescent, 20 to 22 times; an adult (beginning at age 25), 16 times. Over the course of your life, you’re likely to take about 850 million breaths.
As a mammal, you get ‘milk teeth’ by the end of your first year, then a second set that emerges as you leave infancy. When children start school, most of them have all of their baby teeth, which they’ll lose before they’re 12. By 13, most children have acquired all of their permanent teeth except their wisdom teeth. The third molars, or ‘wisdom teeth,’ usually emerge between ages 20 and 21; their roots mature between ages 18 and 25. As you age, your plaque builds up, your gums retreat, your teeth wear down, and you have more cavities and periodontal disease. The last few years, as my father’s gums have shrunk, bone hase rubbed up against his dentures, causing pain whenever he chews.
Children’s fingernails grow one millimeter a week. Toenails grow one-quarter as fast as fingernails – one millimeter a month. Pianists’ and typists’ fingernails grow faster than others’. Fingernail growth is fastest in November, slowest in July, and less rapid at night. The first and fifth digits grow more slowly; in severe cold weather, fingernails grow more slowly. From age 30 until 80, fingernail growth slows by 50 percent. Contrary to myth, Dad, your nails and hair don’t keep growing after you die. – The thing about life is that one day you’ll be dead, David Shields