Re: Poached: Is Lucy our ancestor?

Bob Casanova wrote:
On Tue, 25 Nov 2008 19:10:58 -0800, the following appeared
in talk.origins, posted by John Harshman
<jharshman.diespamdie@xxxxxxxxxxx>:

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

<snip>

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.

No, that's not what I think is silly. But what do we know other than reasoned conclusions from evidence? Wouldn't that characterize all parts of the continuum?

Certainly. But I'm sure you agree that some conclusions are
more likely to be correct, based on the evidence, wouldn't
you? And thus instead of being "silly", you seem to agree
that there *is* a difference between "reasoned conclusions
based on the evidence and what we know", unless, of course,
there's no continuum after all.

If that was what you were trying to say, you express yourself very badly. OK, some conclusions are stronger than others. Now what?

Now what did you mean by "when we have strong evidence"? When would we ever have strong evidence? If we never would, why did you mention it at all?

I'd assume that would be determined by the researchers
actually doing the work. As merely an interested layman, I
certainly can't make that determination, but I'd assume
*someone* can.

Yes, I can. There is no evidence on which to base strong conclusions of ancestry, except for noticing the paraphyly of a biological species in the present day.

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?
No. It means we are unable to assign ancestral status to real fossils. Of course such relationships exist, though it seems unlikely, given the small proportion of species estimated to be preserved as fossils, that we actually have any examples of ancestors, even if we can't tell.

Now that's a point I hadn't considered - the fact that known
fossils are assumed to comprise only a minor part of all
species which ever existed would indeed make it unlikely
that we have actual ancestor/descendant fossil pairs
available. Thanks!

Just to confuse you more, one caveat: some taxa are more preservable than others, so it might be possible to believe we have a fairly complete sample of species within some taxon over some range of space and time. But I don't know of any useful cases.

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.
Of course they are. They're saying things are true that we have no way of knowing. I would consider that to be violating some kind of rule. It's certainly not science.

Hmmm...OK. But are scientists not allowed to speculate when
they have evidence, even though that evidence isn't
conclusive? Informed speculation doesn't equal making untrue
statements.

There is no such evidence; that's what I'm trying to tell you. There is no conceivable fossil evidence that would show one species to be ancestral to another, unless we knew somehow that we had a complete sample of all species in the taxon. And we have no way to know that. Such speculation isn't based on facts; it's divorced from the facts, and it's for the purpose of hyping one's research -- it sounds so much more interesting to have the ancestor of all turtles than just another fossil turtle.

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.

True.

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.

I don't refuse to use the term. I merely refuse to say that your great-grandfather is Prince Albert, since I have no information on the identity of your great-grandfather. More, since nobody has that information (follow the analogy here; I don't care if you know who your great-grandfather was), it's wrong for anyone to claim that Prince Abert was your great-grandfather. It's perfectly fine to claim that you had a great-grandfather.

Since I specifically stated that we don't know his identity
I'll take this as agreement.

Yes, but once we leave the analogy, where does that get us with fossils? Just that we agree that species had ancestors.

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.

And I say it's valid unless we're trying to assign ancestral identity to some particular species.

OK; that was my initial point, that it's OK to use, but not
abuse, the term. I thought from your initial comments that
you didn't agree with this, but since you do there's really
not much more to discuss on this point.

Every use you have mentioned is abuse of the sort I'm talking about. Nobody is talking about ancestral species in the abstract. They're always pointing at some particular fossil.

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.
I find this particular line of discussion too boring to argue about.

Your option. But I don't think it can be refuted; we really
*don't* have what would be considered scientific evidence of
patrimony in any but a tiny minority of cases.

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.
Whatever you mean by that.

If you don't see that a term can be useful as a concept
during discussion without making it a concrete declaration
of identity there's not much more I can add.

I agree with the statement, but it seems a pointless thing to assert. Nobody has been arguing against it.

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.
Most of the evidence you are talking about here either doesn't exist or is not good enough to be useful for the purpose you're trying to put it to.

OK; it was an idea apparently based on faulty assumptions
regarding the state, and amount, of information available
about both genetics and the fossil record (as previously
noted). So let's just say that we have no good information
regarding either male ancestors or ancestral species.

You can say what you like, but don't include me.

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

OK.

But you're still wrong. I want that to be clear.

In some ways, yes. But you've agreed that using the term
"ancestral species" is OK so long as it isn't misused to
falsely identify specific pairs, which was my main initial
point.

If that was your point, I have no idea why you made it. Nobody is using "ancestral species" in the abstract, and nobody was complaining about such use.

And just for the record, I've greatly enjoyed both our
recent exchanges, and I think I learned quite a bit, at
least about the differences between the mindsets of
scientists and engineers (and confirmed *once more*, as if
it needed confirmation, that any engineer who thinks he's a
scientist is dead wrong; the jobs and required modes of
thought differ considerably). Thanks again!

You're welcome?

.

Relevant Pages