In article <1993Jun9.152257.24832 at husc3.harvard.edu> gisselbr at husc8.harvard.edu
(Stephen Gisselbrecht) writes:
>In article <1v4t1s$jth at access.digex.net> stephen at access.digex.net (stephen balb
>>However one could conclude from this that if I bred only large mice that
>>over time my mice would become larger and larger - but eventually the mice
>>will only get so large before they become sick, or sterile or still born -
>>there is a certain mice'ness that can not be selectivly bred out.
>>So how does nature form entirely new animals?
> [...] New species
>arise when a gradual drift in one or some of these traits is combined with
>an event that creates separate breeding populations.
> Okay, I think I'm done. I'm no evolutionist, so tear it to
>shreds--I have no ego invested.
I believe that this is only one _hypothesis_ as to the mechanism of evolution.
Some people think / have thought (eg. Goldschmit sp?) that evolution takes
via. a mechanism (called punctuated evolution by Gould) which involves sudden
catastrophic changes in a taxon giving rise to a new taxon.
These changes could involve mutations in single genes with pleiotropic effects,
especially in controlling genes that code for transcription factors. Note
that in Drosophillia sp? a single mutation can change this two winged fly
into a four winged fly (just the opposite to what is supposed to have
occurred during evolution ...
A more coherent statement of this point of view can be obtained by looking
up articles written by Gould and Goldschmidt ...
Randall Tyers tyersome at insect.berkeley.edu
(also not an evolutionist - but I might be right anyway)