Re: New finds

["philidor11" <philidor11@snet.net>]

Just found this reply.
I tried the formulation:
<Any single species has one and only one ancestral species at any point in
its evolutionary history.  A diagram of the evolution of any contemporary
species will show a straight line with offshoots from the main stem.>
HP Marjanovic observed:
<Under many (not all) definitions of species a species can have 2 (more or
less closely related) ancestral species at the same point in its
evolutionary history. Speciation by hybridism is common among plants (for
those who agree to call that speciation). In any case, the straight line is
a consequence of presentation that means nothing in reality, and so is the
main stem. :-)>

First, the definition of a species appears to me just about intractable.
Still, I use the fertile offspring definition, which would make two
'species' able to hybridize subspecies.
Second, the 'straight line' evolutionary diagram would be of value if it
could be relied upon.  The problem is not with the concept of the line of
descent, it's with the highly contentious nature of any attempt to provide
specific names of ancestors.
Are you really more comfortable with affirming the ability to describe
ancestral forms than with saying that these ancestral forms existed?