Death: Encyclopedia II - Death - Interpretations of death

Death - Interpretations of death

In almost all societies, death has one or several symbols associated with it. Common symbols of death in Western cultures include the grim reaper and the color black; conversely, in certain Eastern cultures, the color white is considered symbolic of death. The grave is a metonym for death.

Biologically, death can occur to wholes, to parts, or to both. For example, it is possible for individual cells and even organs to die, and yet for the organism as a whole to continue to live; many individual cells live for only a short time, and so most of an organism's cells (except for nerve and muscle) are continually dying and being replaced by new ones.

Conversely, when organisms die, their cells can live for some time afterward. Organs can be removed for transplantation. They must be removed and transplanted quickly after the body dies, or they too will soon die without the support of their host. Rarely, cell cultures can be "immortal" as in the case of Henrietta Lacks' HeLa cell line, used in tissue culture research.

Fingernails and hair appear to grow after a person's death, as, due to bodily dehydration, the flesh shrinks away from them. In ancient times, this led to confusion about whether a body was actually dead, and added to the myth of vampires.

Irreversibility is often cited as a key criterion of death. By definition, a dead organism cannot be brought back to life; if it were to be, that would indicate that it had never been dead. Biochemically, it is unrealistic to think that death could be reversed. As soon as tissues die, autolysis sets in and enzymes begin to destroy the cells. Nonetheless, many people do not believe that death is irreversible; thus some have a religious belief in bodily or spiritual resurrection, while others have hope for the eventual prospects of cryonics or other technological means of reversing what is currently thought of as death.

It has been hypothesized that a limited lifespan is a consequence of evolution not selecting for extreme longevity in most species, as evolutionary selection only need apply to the organism up to the point of reproduction; after that, except for rearing offspring and caring for kin, the continued existence of an individual can have little effect on the survival of its gene line. A common misconception is that the Second Law of Thermodynamics dictates that all complex systems must eventually deteriorate, so it is not likely that any species could ever be immortal. However, this aspect of the Second Law applies only to closed systems, which organisms are not.

There is an (as yet unproven) conjecture about the role of telomeres in a countdown toward death, as they shorten with each successive cell division. The theory is that when they run out, additional divisions become impossible, and the cell line eventually dies. This conjecture has been raised again in the use of cloning for reproduction. Telomeres can be lengthened by telomerases, which are present only in germ cells. If short telomeres are present when the new organism begins, it might have only a short lifespan.

Adapted from the Wikipedia article "Interpretations of death", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki