Hypothetical ancestors

[Curtis Clark]

At 02:43 PM 2/12/2002, STEPHEN MANNING wrote:
>Our traditional paradigm is that life
>originated only once, and this is sometimes dogmatically put forth, but if
>the early earth's environment was more conducive to life originating once,
>why would it not be more likely to have happened multiple times in that
>environment?  If we do chemical reactions in test tubes, we don't then say
>that the products of those reactions, which may be indistinguishable, had
>to come from a common ancestor.  In the "primeval soup", life's progenitors
>may well have been hardly more distinguishable from each other than two
>pieces of plastic from the same manufacturer.  So don't fall into the trap
>of being almost as dogmatic as the creationists are by insisting on
>monophyly to the exclusion of parallel evolution.

But there's evidence. All life (that we know of) shares the apomorphy of
the basic genetic code. Even if one accepts recent studies showing that the
actual genetic code is one of the most redundant (and thus a likely result
of selection), there are still other redundant genetic codes that life
*could* have evolved (and perhaps did). Multiple origins or not, all the
evidence points to extant life being a single lineage.


--
Curtis Clark                 http://www.csupomona.edu/~jcclark/
Biological Sciences Department             Voice (909) 869-4062
California State Polytechnic University      FAX (909) 869-4078
Pomona CA 91768-4032  USA                 jcclark at csupomona.edu