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From: emigh@ecsvax.UUCP (Ted Emigh)
Newsgroups: net.bio
Subject: Re: What's this LIFE stuff?
Message-ID: <2103@ecsvax.UUCP>
Date: Mon, 6-Oct-86 22:25:41 EDT
Article-I.D.: ecsvax.2103
Posted: Mon Oct  6 22:25:41 1986
Date-Received: Sat, 11-Oct-86 01:41:49 EDT
References: <45500088@uiucdcs> <7670@tekecs.UUCP> <829@jplgodo.UUCP> <2446@phri.UUCP>
Reply-To: emigh@ecsvax.UUCP (Ted Emigh)
Organization: NC State University
Lines: 36

In article <2446@phri.UUCP> lonetto@phri.UUCP (Michael Lonetto) writes:
>In order for something to be alive it need not be
>reproductively competent (my grandmother doesn't look at all dead yet,
>even though she's well past menopause).
...

>Unfortunately I can only give examples from life as we know it,...
...
>Note that this
>discussion leaves out entirely the more complex issues which sometimes
>arise with complex organisms: is a brain dead person who's heart is
>still beating alive? 

This discussion points up the problem of ALIVE vs LIFE.  Alive is an
attribute of an individual (it is alive, it is dead, it is not alive).
Life is an attribute of a group (class, ...) of individuals.  While a human
individual may have Down's Syndrome, Turner's Syndrome, Triple X Syndrome,
Testicular Feminization, etc, and not be able to reproduce INDIVIDUALLY,
it is a member of a class of individuals (humans) that are able to
reproduce.

As a population geneticist, I tend to view LIFE in population terms.  A
quick (and very dirty) definition of life is something that is a member of
a population (group) which can reproduce itself ALMOST EXACTLY.  By almost
exactly, I include the condition that difference (mistakes) in replication
are passed on in successive generations.  This excludes crystals, but does
include viruses.  The other conditions that have been mentioned simply are
the various strategies (or the common Earth strategy) for doing this.


-- 

Ted H. Emigh     Genetics and Statistics, North Carolina State U, Raleigh  NC
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