Martian human species

[Ken Kinman]

Tom,
    When you state "both species retain the same relationship with the
ancestral species," to me this is at best misleading.  The way I would look
at this Mars man example, Mars mankind budded off of Homo sapiens (Earth
mankind), and the current consensus (although contested) is that Homo
sapiens budded off of Homo erectus.
    H. erectus is thus paraphyletic with respect to H.
sapiens, and the latter would be paraphyletic with respect to the new
species of Mars mankind.  Therefore, Mars mankind is only related to H.
erectus through the genetically intermediate species H. sapiens.  I really
cannot understand why cladists find this viewpoint so
disconcerting.
     If you raise H. sapiens to superspecies status, then I
assume you are going to give Earth mankind a new species
name.  If Earth mankind has not changed (having stayed in the original
environment of Earth), then erecting a new name is misleading.  It seems
more straightforward to retain the original name for Earth mankind and
regard it as a paraphyletic "mother" species to the Mars mankind species.
     And given the continuity of evolution (with rare exceptions, like
polyploidy), I fail to see how your viewpoint is not also arbitrary.  Can
anyone say at what point in time Mars mankind became completely
reproductively isolated from Earth mankind.  Do you draw the line where 95%
of test cross-breedings are unsuccessful, or at 99%, or at 99.99%.  It can't
be 100% unless you want to arbitrarily define hybrids out of existence, and
that would create more problems.
     If you have adequate data, I think mother-daughter species are a more
accurate model, and that sister-sister species should be used when adequate
data is absent.  Since time and extinction have wiped out huge amounts of
data, sister groups will always be useful in most cases, but that should not
prevent us from recognizing mother-daughter groups when adequate data is
available.  Then the only debate will be over what constitutes adequate
data, but in most instances a consensus should be possible without too much
dissent.  To insist that we must only recognize sister groups seems
short-sighted to me.
                         -------Ken Kinman

> >>Tom DiBenedetto originally wrote:
> >>If we sent a colony off to
> >> Mars, and they became reproductivly isolated, then the
taxon Homo sapiens would no longer be a species level
taxon, it would refer to a
> >> more complex lineage, and would be a higher taxon.
Nothing has "gone extinct" or disappeared.

>Richard responds:
> >Given that you have used a specific criterion in your
example (reproductive isolation), then I would argue that the taxon Homo
sapiens is still a species (those on Earth), and those on Mars represent a
new species of Homo (H. ares?).  Those on Earth still behave
as a single taxon
> >consisting of a large number of reproductively
compatible individuals.
>
>Tom responds:
>The humans who would remain on earth still function as a
species, in an unbroken chain with the ancestral humans,
but so do the martians. It is simply that the martians and
the earthlings do not interact in a
>genalogical manner with each other. So both are species
unto themselves (post-split), but both also retain the same
relationship with the ancestral species. The ancestral
taxon, named and identified as a
>discrete unit, without one or more of its descendants
would be paraphyletic. It would be an artifical naming
decision. The ancestral taxon now encompasses both of its
descendants, by the very criterea by
>which we recognize any taxon (ancestor and its
descendants). The ancestral taxon IS a higher taxon,
encompassing two daughter species.
>I think this is what Hennig was trying to approximate with
his "species go extinct at branching" notion. It would have
been better put as "species-level taxa are promoted to
higher level taxa at branching". I
>dont understand why there is resistance to the notion that
our systematic ranks (which should be tied to the hierarchy
of taxic divergence) should evolve as the taxa themselves
evolve.
>
> >I don't see the necessity of raising H. sapiens to a
higher taxon.  As you
> >say, nothing has gone extinct or disappeared.  If a have
a species, and
> >nothing goes extinct or disappears, then I still have a
species.
>
>But it seems obvious to me that if we are to take
evolution seriously,
>we must recognize that this species that you have has two
sets of
>descendants, which do not share genes with each other.
Clearly both
>descendants are functioning as species, and clearly both
have the same
>relationship with the ancestral species as the other, so
both should
>have the same taxonomic identity relative to the ancestor.
And if both
>are species, then the ancestor and its descendants form a
higher taxon.

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