Re: Poached: Is Lucy our ancestor?

On Sun, 23 Nov 2008 16:18:06 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

Bob Casanova wrote:
On Sat, 22 Nov 2008 17:58:39 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

Bob Casanova wrote:
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.
Shouldn't we avoid it except in those few cases in which we can 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.
It's useful because we can't apply it?

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.
What's the point? None of those pairs is any more valid.

Not even as "most likely based on morphology and on what we
know of evolution and the environment of the particular
species"?

No.

Is everything black/white; either we know
absolutely the identity of the ancestral species or we
cannot even claim there *was* an ancestral species? Sounds
awfully rigid to me...

Sounds that way to me too, which is why I never claim anything so silly.

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.
Yes, and the term is appropriately used in purely hypothetical cases,
such as when we refer to the common ancestral species of, say, humans
and chimps. But I fail to see how that makes it appropriate in cases
where we can't possibly know.

We can't possibly *know* anything which we didn't experience
directly or which didn't leave unambiguous evidence; we can
only make reasoned conclusions based on the evidence. So
there's no meaning in the term "thought to be the ancestral
species"?

You have to stop putting words in my mouth.

Sorry; I though it was a reasonable interpretation of your
statements.

Everything in that paragraph
also sounds silly to me.

I'm curious; is it silly to say that we don't know that for
which we don't have direct experience or unambiguous
evidence, or is it silly to say we can make reasoned
conclusions based on the evidence we do have? If the former,
why can't we assign "ancestral species" as a designator when
we have strong evidence? And if the latter, why do we bother
to attempt to construct lineages, such as the "horse" or
"whale" ones?

Except the last sentence; it isn't that there
is no meaning, but that it refers to a condition we can't reasonable say
anything about.

So we can't even say "We believe, based on the available
evidence, that eohippus was ancestral to mesohippus, and
that mesohippus was ancestral to equus"? If this is your
belief, why bother to construct even tentative lineages?

What are you trying to say here?

I thought I said it:

You were wrong.

Funny, but since it's what I said it seems that I was right
that I said it. This doesn't, of course, address whether you
agree with it.

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.

Since ancestral species definitely exist, refusing to use
the term in any but hypothetical discourse seems to me
equivalent to refusing to use the term "father", since in
most cases the identity of the father, like the identity of
the ancestral species, is a matter of conjecture.

You are wrong. In most cases we have a pretty good idea about fathers.

No, we have an *assumption* about fathers, based on
testimony. We almost never have genetic corroboration.

In almost all cases we have no good idea about ancestral species.

I'd say that based on actual evidence, as contrasted with
anecdote or unsupported claims, we have more evidence about
ancestral species, particularly extant or recent ones, than
about fathers. Mothers, yes. Fathers, no.

Calling something an ancestor when we have no way of determining if it's
an ancestor, even on a probablistic basis, is just dishonest.

Of course, YMMV, but I think that as in our "fact/theory"
discussion of a few weeks ago we'll simply have to agree to
disagree.

Let's agree that you're wrong.

Sorry, but I have to disagree.
--

Bob C.

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

.

Relevant Pages

  • Re: Poached: Is Lucy our ancestor?
    ... only make reasoned conclusions based on the evidence. ... why can't we assign "ancestral species" as a designator when ... identity of the great-grandfather in question. ... an ancestor, even on a probablistic basis, is just dishonest. ...
    (talk.origins)
  • Re: Poached: Is Lucy our ancestor?
    ... only make reasoned conclusions based on the evidence. ... why can't we assign "ancestral species" as a designator when ... In most cases we have a pretty good idea about fathers. ... an ancestor, even on a probablistic basis, is just dishonest. ...
    (talk.origins)
  • 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 ... 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)