> I would use the word "destroy" rather than kill for something that is not
> alive.
>
More word games. First of all, it is grammatically correct to say you
destroyed a dog, while it is not grammatically correct to say you killed a
stone. So the word "destroy" is equally valid when applied to life as
non-life. Secondly, one of the meanings of "destroy" given in the dictionary
is "to kill", so the word can mean "to cause life to cease" just as kill does.
In any event, before you can decide which is more appropriate, "kill" or
"destroy", you have to know if the subject is alive or not. Fox has proven
that his protocells are alive, so "kill" would be the most appropriate term.
Go read the scientific literature.
>
> It is true what I have heard that one can use very old cells to clone
> a long dead animal? Is that true?
>
You mean as in _Jurassic Park_? It is theoretically possible, but the
technology needed is beyond our current capability. Besides, the DNA needed
could not come from cells, since the cells would have long since died and
broke apart, but from the fossil matrix.
>
> If true, how old can those cells be?
>
The cells would no longer exist. When the animal died any cells that were
still alive would starve, suffocate, be eaten by bacteria or poisoned by
them, and so would disappear. The DNA might survive, in pieces, but there is
controversy at present over how long DNA can be preserved even under the best
conditions.
>
> Do such cells ever die?
>
Of course they can. If they did not self-destruct, they more than likely
starved/suffocated when the lack of blood flow cut off their food and oxygen,
or they were poisoned by the putrifaction going on around them. Even cancer
cells can be killed; they just don't die by wearing out or committing suicide
like normal cells can. Cells die when their metabolic systems shut down or
if their membranes are broken. The former can happen because there is a lack
of glucose, amino acids or fatty acids to provide energy; there is a lack of
oxygen to pick up the waste electrons produced when the cell releases the
energy in glucose to produce heat and ATP; toxins inhibit the enzymes;
radiation destroys the genes; or a gene is triggered that activates a
metabolic mechanism that shuts overall metabolism down. In the absence of
these conditions, however, there is no reason why a cell cannot continue to
live indefinately.
Fox's protocells die when their metabolic systems shut down or their
membranes are broken, just as with real cells. Otherwise they continue to
live indefinately as well. By your reasoning we should conclude that since
protocells die like modern cells, they should be considered alive like modern
cells as well.
Kevin L. O'Brien