Cladistics and "Eclecticism"
Hovenkamp at NHN.LEIDENUNIV.NL
Thu Feb 7 11:44:25 CST 2002
At 10:49 AM 2/5/02 -0500, Thomas DiBenedetto wrote:
> >Two questions, well, three actually:
> >1. If a group of people (say, a mixed group of 100 men, women and children)
> >embarked on a spaceship and were to settle on Mars - would that effectively
> >split Homo sapiens into two species (assuming contact would be scarce and
> >limited to raw materials, not frozen sperm etc.) the moment the spaceship
> >took off?
> >2. If a group of people (say, a mixed group of 100 men, women and children)
> >embarked on a plane which later crashed into a high mountain in the Andes
> >(alas, no survivors) - would the situation to us survivors on the ground
> >(and in other planes) be different in any way from the situation we would
> >have had in the first case?
> >3. Considering the fact that (2) is a fairly common occurrence, are we
> >still in the same species as we were this time last year?
>Anyway, as far as I can make out from this post, your answers are Yes, No,
>I guess my decision to save some time was a bad one. I should have simply
>answered your questions. My answers would be No, Yes , and Yes. I must be
>pretty inarticulate to have given you reason to conclude the exact opposite.
>I will try harder.
>The criterion for demarcating species, as well as any other taxon, is
>_relationships_ among groups. There is nothing that has changed from last
>year to this year about the nature of the relationships between our species
>and other species. So queston 3 is obviously Yes. The establishment of a
>new group, a new species evolutionarily isolated from us _does_ change the
>nature of the relationships between our species and other species. So the
>answer to question 1 would be Yes eventually - but since you stipulate "the
>moment the spaceship took off" I would have to say No - not yet. I don't
>know what the point is of trying to pin down the "exact moment of
>speciation" - I don't suspect that that is something that could ever be
>done, or that has much meaning. But I will stick with a "No, not yet" answer
>because clearly the astronauts cannot be said to have established their new
>species yet, in any real sense.
>A group of people dying does not change the nature of the relationships
>between our species and other species. So question 2 is clearly Yes.
>What's your point?
Clarification by way of thought experiment.
As I understand it now, in your view the existence of species is dependent
on the success of the colonizers "in any real sense". What I wonder about
is how this can be made into an exact distinction (sorry - if you don't see
any use for exactness, you'd better withdraw from this thread). How much
success is required? How viable must the new lineage be? If a short-term
lineage is established, does that permanently split the fabric of the
species? Did any lineages "back-speciate" when the Dodo went extinct?
In the above thought experiment, all may depend on the question whether or
not abortion is allowed during a space flight of more than 9 months...
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