Re: Poached: Is Lucy our ancestor?

On Mon, 24 Nov 2008 16:15:40 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

Bob Casanova wrote:
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:

<snip>

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?

It's silly to distinguish between reasoned conclusions based on the
evidence and what we know.

Well, I see knowledge as a continuum, from "we know this to
be factual" to "we don't have the foggiest notion", with
reasoned conclusions based on evidence in between, but much
closer to the "we know" end. If to you that's "silly", so be
it.

If the former,
why can't we assign "ancestral species" as a designator when
we have strong evidence?

What would that strong evidence be?

Where did I claim to have any? You reject "ancestral
species" as a concept unless we know what the relationship
between particular pairs of species is; I say that we can
use the term as a general descriptor, without knowing
whether a particular pair has such a relationship. The one
thing we *do* know is that every extant species has an
ancestral species; whether we know what that species may be
in a particular case is irrelevant to the concept.

And if the latter, why do we bother
to attempt to construct lineages, such as the "horse" or
"whale" ones?

We, meaning scientists, don't. What can be constructed are the histories
of character transformation, as distinct from the ancestor-descendant
sequences of species.

Fair enough. Does this mean that no one even considers
whether such relationships exist?

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?

I don't. It used to be a popular sport among paleontologists. It isn't
any more.

Again, fair enough. But note that that's your preference,
not a general rule, and that anyone who *does* make such
statements isn't, AFAIK, violating scientific protocol.

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.

What I'm trying to address is what the heck you thought you meant.
That's not clear to me. I assume you were trying to make some point, and
you have not, at least to me. I also assume that what you were trying to
say made some kind of sense, whether I would agree with it or not.

Try this: Every extant species is a descendant of a previous
species, which may or may not still be around. This being
the case, to refuse to even use the term "ancestral species"
unless we know in a particular case *which* pair of species
bears this ancestor/ descendant relationship is equivalent
to refusing to use the term "great-grandfather" to refer to
the ancestor of a particular individual if we don't know the
identity of the great-grandfather in question. Whether we
know his identity or not is irrelevant to the fact that we
know he existed, and we can use the phrase "Your
great-grandfather contributed at least one-sixteenth of your
genes" whether or not we know his identity. IOW, I'm saying
that the term "ancestral species" is valid for discussion
whether or not we know the identity of that species or not,
or even whether we're talking about a particular descendant
species. It's a matter of discussion, not of publication of
a paper.

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.

Generally our assumptions are correct. Often phenotype is good evidence.

.....and sometimes it's not. But without genetic testing we
can only take the mother's word for it; IOW, we rely on
anecdotal evidence.

This has nothing to do with declaring ancestral species.

So? You're the one stuck on the idea of "declaring"; I
merely think the term can be useful as a concept.

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.

On what basis would you say this?

The fact that we almost never have anything but anecdotal
evidence regarding patrimony, while there is abundant
evidence from genetics (of extant species, indicating
relational proximity and thus the general timeframe of
separation) and the fossil record (which can be used to
check which species appeared and disappeared at which
general times, and where, and thus provide a link to the
genetic relational data) which tends to suggest which
species are likely to have come from which.

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.

We can agree to disagree about whether you're wrong.

OK.
--

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?
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  • 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. ...
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