RC 03 - NOV 09

The possibility of untimely death is frightening, but the inevitability of ageing and dying casts the longest shadow on human life.

Humankind's efforts to overcome aging have been impressively persistent. We have, however, not succeeded. By age 80, half of us will

die; by age 100, 99 percent; and by about age 115, every one of us will be dead, medical breakthroughs notwithstanding.

During the past few hundred years, the average length of life (life expectancy) in modern societies has steadily increased, but the

maximum duration of life (life span) has not. Centuries ago a few people may have lived to 115; today this maximum remains about the

same. All the wonders of medicine, all the advances in public health have not demonstrably increased the maximum duration of life. If

ageing is a disease, it seems to be incurable.

Technically, we are not really talking about ageing, the process of growing older from birth onwards, but senescence, the process of bodily

deterioration that occurs at older ages. Senescence is not a single process but is manifested in an increased susceptibility to many

diseases and a decreasing ability to repair damage. Death rates in modern developed countries are very low at age 10 to 12, about 0.2

per 1000 children per year. The death rate increases slowly to 1.35 per 1000 at age 30, then increases exponentially, doubling every 8

years. By age 90, the death rate is 169 per 1000. A person aged 100 has only a one-in-three chance of living another year. Every year the

mortality curve becomes steeper, until eventually we all are gone.

Imagine a world in which all causes of premature death have been eliminated, so that all deaths result from the effects of ageing. We

would live hearty, healthy lives, until, in a sharp peak of a few years centred at age 85, we would nearly all die. Conversely, imagine a

world in which senescence is eliminated, so that death rates do not increase with age but remain throughout life at the level for eighteenyear-

olds, that is, about 1 per 1000 per year. Some people would still die at all ages, but half the population would live to age 693, and

more than 13 percent would live to age 2000! Even if death rates were much higher, say 10 per 1000, eliminating the effects of

senescence would still give a substantial advantage, with some people living to age 300. From an evolutionist's point of view, an individual

who did not senesce would have, to put it mildly, a substantial reproductive advantage.

This brings us to the mystery. If senescence so devastates our fitness, why hasn't natural selection eliminated it? This possibility seems

preposterous only because senescence is such an inescapable part of our experience. Consider, however, the miracle of development:

from a single cell with forty-six strands of nucleic acid, a body gradually forms, with each often trillion cells in the right place, making

tissues and organs that function together for the good of the whole. Certainly it should be easier to maintain this body than to form it!

Furthermore, our bodies have remarkable maintenance capacities. Skin and blood cells are replaced every few weeks. Our teeth get

replaced once. Damaged liver tissue can be rapidly replaced. Most wounds heal quickly. Broken bones grow back together. Our bodies do

have some capacity to repair damage and replace worn-out parts; it is just that this capacity is limited. The body can't maintain itself

indefinitely. Why not?

Q1

What is the topic of this passage?

1) The cruelty and mystery of death

2) The search for a cause of ageing and death

3) The unavoidability of senescence and death

4) The evolutionary explanation for senescence

Q2

According to the author:

1) Over the last few centuries, life spans have increased gradually.

2) More people now live up to the age of 115 than they did in the past.

3) It would be better if senescence rather than premature death could be eliminated.

4) Senescence is unavoidable since natural selection has not eliminated it.

Q3

What is the structure of this passage?

1  A topic is introduced via some definitions and statistics; some hypothetical ideas are suggested; another perspective on the

topic is mentioned; a mystery is left unresolved.

2)A topic is introduced; some statistics and definitions regarding it are mentioned; some counterfactual ideas are suggested;

a question regarding the topic is raised.

3  A topic is introduced; some definitions are clarified; some hypothetical scenarios are mentioned; the issue raised in the

passage is left unresolved.

4)

A topic is introduced with the help of some statistics; an alternative scenario regarding one aspect of the topic is

mentioned; a puzzling aspect of the topic is mentioned