Re: Poached: Is Lucy our ancestor?

On Fri, 21 Nov 2008 14:31:46 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

Bob Casanova wrote:
On Thu, 20 Nov 2008 12:56:42 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

Bob Casanova wrote:

On Wed, 19 Nov 2008 15:30:34 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

<snip>

Or, maybe, as scientists generally do except in press release hype, we
should stop talking about "ancestral species", and stop claiming that
this or another new fossil is the ancestor of some group or other. (I
see there's another new thread about an "ancestral turtle". Doubtful.)

But "ancestral species" is such a convenient designator when
speciation or species succession is the topic of discussion
(especially with laymen such as myself involved) that I
doubt dropping it will happen. It may not be 100% correct
and totally unambiguous, but I think most of us know the
intended meaning.

Do we? What is it, exactly?

I would think it means a species from which another species
arose, either directly or through intermediate species
("Hyracotherium is thought to be ancestral to Mesohippus,
and later to Equus."). Can you think of an alternate
meaning?

No. And that's the problem. It's not true, or at least we can't know if
it's true. Making such claims is problematic.

But they are made nonetheless, and not only by laymen.

Note that I make no claim regarding the *accuracy*
of any particular instance in which one species is claimed
to be ancestral to another, but that's irrelevant to the use
of the term, since *any* such instance would be subject to
exactly the same potential error no matter how the
relationship is expressed.

Not sure what you mean there. We have no way of determining is one
species is ancestral to another. Nobody should be making claims of
ancestry about fossils *or* fossil species. It's possible to make such
claims about extant species on rare occasions, but that depends on
genetic data.

I mean that despite the fact that we really can't tell if
one extinct species is ancestral to another, the term
"ancestral species" still has utility. After all, we can (or
at least, should be able to) tell if one extant species is
ancestral to another, such as the mosquitoes in the London
Underground. Thus the term is useful, even if we can't
always apply it with known accuracy.

(BTW, I cheated by looking up the horse lineage at:

http://www.talkorigins.org/faqs/horses/horse_evol.html

So shoot me; I don't keep these in my head.) ;-)

"Hyracotherium" is almost certainly a paraphyletic assemblage of
primitive perissodactyls. Some of them are closer to horses, others
closer to rhinos. That, we can tell. We can't tell if any particular
piece of Hyracotherium is ancestral to anything, much less to modern horses.

No, and that's why the term "ancestral species", meaning the
species which we think gave rise to a later species, is
useful. We don't have to know which part of one was
ancestral to another (which is where this started, IIRC). If
you don't like the two I picked from the page, there are
several other potential pairs of direct and derivative
ancestral/descendant species shown.

If we're going to claim that there is species succession
(and we seem to) the term is valid, even if we can't apply
it with known accuracy. After all, if speciation exists (and
it seems to) species *are* ancestral to other species,
regardless of whether we can or do apply the term correctly
in particular instances.
--

Bob C.

"Evidence confirming an observation is
evidence that the observation is wrong."
- McNameless

.

Relevant Pages

  • Re: Fossil Record/Common Ancestor Examples?
    ... the modern Equus (still not a species but a genus). ... there is always a temptation to turn a transitional into an ancestor. ... no fossil record for African apes other than hominins. ... bipedalism of Australopithecus species such as Lucy (Australopithecus ...
    (talk.origins)
  • Re: Poached: Is Lucy our ancestor?
    ... in talk.origins, posted by John Harshman ... this or another new fossil is the ancestor of some group or other. ... speciation or species succession is the topic of discussion ... only make reasoned conclusions based on the evidence. ...
    (talk.origins)
  • Re: Poached: Is Lucy our ancestor?
    ... in talk.origins, posted by John Harshman ... this or another new fossil is the ancestor of some group or other. ... speciation or species succession is the topic of discussion ... only make reasoned conclusions based on the evidence. ...
    (talk.origins)
  • Re: Poached: Is Lucy our ancestor?
    ... in talk.origins, posted by John Harshman ... should stop talking about "ancestral species", and stop claiming that this or another new fossil is the ancestor of some group or other. ... only make reasoned conclusions based on the evidence. ...
    (talk.origins)
  • Re: Still waiting
    ... >Perhaps other intermediate species provided the actual transition from ... We can compare those inferred ancestral morphologies to fossils and tell you that this or that fossil resembled the ancestor quite closely, ... It's also often difficult to distinguish an evolutionary transition from immigration. ...
    (talk.origins)