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Books > Science & Mathematics > Biology, life sciences > Cellular biology
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Sex and the Origins of Death (Paperback, Revised)
Loot Price: R578
Discovery Miles 5 780
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Sex and the Origins of Death (Paperback, Revised)
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Loot Price R578
Discovery Miles 5 780
Expected to ship within 10 - 15 working days
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Speculations on life and death from a professor of cellular biology
at UCLA. "We die because our cells die," Clark says. Death is "the
evolutionary consequence of the way we reproduce ourselves." The
sole function of cells, human or otherwise, is to replicate their
DNA; once finished, they are programmed to die. That is, once a job
is done, such as growing fingers out of weblike structures in human
embryos, certain cells have no further task and die. "Programmed"
is a key word here: In a number of clever laboratory experiments,
healthy cells reproduce themselves only to a point, and undergo a
process of exploding outward, called apoptosis. If the process is
blocked, cells have a tendency to become cancerous and, at the
least, will stop dividing. Only cancer cells and certain ancient
single-celled life forms are, in a manner of speaking, immortal,
but they, too, will eventually die by overcrowding or when they run
out of food. Clark proceeds to discuss how the nature of cell death
relates to the agonizing debate over a patient's "right to die,"
detailing the strange findings of Karen Ann Quinlan's autopsy and
relating it to yet another incidence of near-death: the spores
produced by certain animal forms in times when nature makes it hard
to reproduce. The minuscule spores of briny shrimp truly seem to be
dead but, when chilled to absolute zero and placed in the correct
environment, will begin the cycle again. Clark ends by speculating
about so-called "nonsense DNA." Is it a useless relic of the
evolutionary process, or does it hold the keys to an explanation of
why we must die, and even why we are here in the first place? His
discussion of biology flows into a discussion of metaphysics.
Strikingly well argued and clear. (Kirkus Reviews)
Death, for bacteria, is not inevitable. Protect a bacterium from
predators, and provide it with adequate food and space to grow, and
it would continue living--and reproducing asexually--forever. But a
paramecium (a slightly more advanced single-cell organism), under
the same ideal conditions, would stop dividing after about 200
generations--and die. Death, for paramecia and their offspring, is
inevitable. Unless they have sex. If at any point during that 200
or so generations, two of the progeny of our paramecium have sex,
their clock will be reset to zero. They and their progeny are
granted another 200 generations. Those who fail to have sex
eventually die. Immortality for bacteria is automatic; for all
other living beings--including humans--immortality depends on
having sex. But why is this so? Why must death be inevitable? And
what is the connection between death and sexual reproduction?
In Sex and the Origins of Death, William R. Clark looks at life
and death at the level of the cell, as he addresses such profound
questions as why we age, why death exists, and why death and sex go
hand in hand. Clark reveals that there are in fact two kinds of
cell death--accidental death, caused by extreme cold or heat,
starvation, or physical destruction, and "programmed cell death,"
initiated by codes embedded in our DNA. (Bacteria have no such
codes.) We learn that every cell in our body has a self-destruct
program embedded into it and that cell suicide is in fact a fairly
commonplace event. We also discover that virtually every aspect of
a cell's life is regulated by its DNA, including its own death,
that the span of life is genetically determined (identical twins on
average die 36 months apart, randomly selected siblings 106 months
apart), that human tissue in culture will divide some 50 times and
then die (an important exception being tumor cells, which divide
indefinitely). But why do our cells have such programs? Why must we
die? To shed light on this question, Clark reaches far back in
evolutionary history, to the moment when "inevitable death" (death
from aging) first appeared. For cells during the first billion
years, death, when it occurred, was accidental; there was nothing
programmed into them that said they must die. But fierce
competition gradually led to multicellular animals--size being an
advantage against predators--and with this change came cell
specialization and, most important, germ cells in which
reproductive DNA was segregated. When sexual reproduction evolved,
it became the dominant form of reproduction on the planet, in part
because mixing DNA from two individuals corrects errors that have
crept into the code. But this improved DNA made DNA in the other
(somatic) cells not only superfluous, but dangerous, because
somatic DNA might harbor mutations. Nature's solution to this
danger, Clark concludes, was programmed death--the somatic cells
must die. Unfortunately, we are the somatic cells. Death is
necessary to exploit to the fullest the advantages of sexual
reproduction.
In Sex and the Origins of Death, William Clark ranges far and wide
over fascinating terrain. Whether describing a 62-year-old man
having a major heart attack (and how his myocardial cells rupture
and die), or discussing curious life-forms that defy any definition
of life (including bacterial spores, which can regenerate after
decades of inactivity, and viruses, which are nothing more than DNA
or RNA wrapped in protein), this brilliant, profound volume
illuminates the miraculous workings of life at its most elemental
level and finds in these tiny spaces the answers to some of our
largest questions.
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