Hypothetical Common Ancestor?

[David]

http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg

What is a hypothetical common ancestor? Also, do we know the CA for any two species?

[John Harshman]

David wrote:
> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>
> What is a hypothetical common ancestor?

Just what it sounds like. Any spot on that tree except the tips of the
branches is inferred from data, not associated with a known species.

> Also, do we know the CA for any two species?

You open a can of worms that would require us to know whether an
organism in the distant past is the same species as one we see today, or
whether two fossils really belong to the same biological species. I
wouldn't be confident of either. But if you want to make such leaps,
there are a few.

[Richard Norman]

Imagine the situation given that every human on earth today is a
descendant of Adam and Eve. Then it would necessarily be true that
for any two particular people now alive there must be a most recent
common ancestor. The most recent ancestor would almost certainly have
lived well after Adam and Eve and well before the present day. That
hypothetical most recent common ancestor must exist but is entirely
hypothetical since except in a few cases of close relatives with good
genealogical records we have no way of finding out just who it was.

The same reasoning applies in evolution. The hypothetical common
ancestor must exist and we can make very good guesses as to what it
might have looked like. We can find fossils that look very much like
the common ancestor but there is no way of determining that that
particular fossil was, indeed, THE common ancestor or merely a close
relative of the real one.

[Ron O]

On Jul 7, 3:17 pm, David <david.neff1...@gmail.com> wrote:
> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>
> What is a hypothetical common ancestor? Also, do we know the CA for any two species?

Your figure illustrates the broad phylogenetic branch points and isn't
fine enough in detail to get at your request. The figure isn't to
scale in terms of time. Humans and chimps had a common ancestor just
around 5 million years ago and feathers evolved well over 100 million
years ago. The accuracy of the figure may be in doubt (Where they
have placenta under mammals they likely should have eutherian because
both eutherian and marsupials have placenta. It looks like your
figure is just trying to show the major points of what we call a
nested heirarchy. You have traits nested within traits due to descent
with modifications. You have vertebrates (including fish to
mammals). You have terrestrial vertebrates from amphibians to
mammals. You have amniote terrestrial vertebrates (reptiles, birds
and mammals). The branch point of crocodiles and birds from reptiles
and their relationship with mammsls seems to be messed up on this
figure. Mammals are more closely related to crocs and birds than to
snakes and lizards.

For something like the chimp and human common ancestor it has to be
inferred from the genetic evidence. Just as there is a nesting of
traits shown in your figure there is a nesting of genetic changes over
time. We can tell that a fish genome evolved from a more primative
cordate genome. The amphibian genome evolved from a fish genome. The
terrestrial amniote vertebrate genome evolved from an amphibian
genome. The egg laying mammalian genome evolved from something that
most people would call a reptile, but the purists call it a synapsid.
The eutherian and marsupial mammal genomes evolved from an egg laying
mammalian genome. Primate genomes evolved from a eutherian genome and
chimps and humans evolved from a primate genome. You can tell this by
the nested similarities and differences.

Just as we know that second cousins are related to a great grand
parent that they have in common by genetic testing, even if we don't
have the great grand parent's DNA, we can tell that chimps and humans
shared a common ancestor using the DNA evidence. We don't have to
know who that great grand parent was just that the DNA evidence says
that they existed.

To try to identify the common ancestor using fossils is pretty
futile. There are so many closely related species existing at any one
time that when you find a fossil that looks right for the common
ancestor you can't really tell even if it falls at the expected point
in time. Just look at how many deer species there are around the
world and then project out 5 million years into the future when most
of those species are extinct and try to figure out which deer like
species was the common ancestor of what survived. All you will
basically know is that the common ancestor looked something like a
deer.

You can identify the ancestor of more recent species. The easiest
example are the amphidiploids (mostly plants). These are
allotetraploids that are new species due to the hybridization of two
existing species and the tetraploidization of the resulting hybrid
product. When a hybrid is created between two different species it is
usually sterile, but by a quirk in mitosis the chromosome number can
double and now there are good pairs of each chromosome from each
parent species. The resulting species is genetically isloated from
both parents and has many more chromosomes than either parent
species. There are examples of this that have been identified in the
field where the parental species still exist. So you essentially have
a branch point where you have the original species coexisting with the
new species. All vertebrates from fish to mammals may have evolved
from a common ancestor that evolved either as a tetraploid or an
allotetraploid. All vertebrates share that original doubled genome.

There are other methods of speciation, but that is one of the easiest
to observe and it has had a big impact on vertebrate evolution, and we
can identify the species that the new species evolved from.

Ron Okimoto

[Ernest Major]

In message
<41f52cf2-85fc-4250...@a34g2000yqi.googlegroups.com>, Ron
O <roki...@cox.net> writes

>The branch point of crocodiles and birds from reptiles and their
>relationship with mammsls seems to be messed up on this figure. Mammals
>are more closely related to crocs and birds than to snakes and lizards.

He has this right. There doesn't seem to be any doubt that lepidosaurs
and archosaurs are both sauropsids, whilst mammals are synapsids. There
is, I believe, a little question about the positions of chelonians, but
he omitted them from the tree.
--
alias Ernest Major

[chris thompson]

On Jul 7, 4:17�pm, David <david.neff1...@gmail.com> wrote:
> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>
> What is a hypothetical common ancestor? Also, do we know the CA for any two species?

In answer to your second question, yes we do.

I like to point people to the genus _Spartina_. There have been at
least 2 speciation events in a single human lifetime.

Ernest Major can point you to more,

Chris

[Ron O]

On Jul 8, 11:59 am, Ernest Major <{$t...@meden.demon.co.uk> wrote:
> In message
> <41f52cf2-85fc-4250-871b-0daf3c1d3...@a34g2000yqi.googlegroups.com>, Ron
> O <rokim...@cox.net> writes

>
> >The branch point of crocodiles and birds from reptiles and their
> >relationship with mammsls seems to be messed up on this figure. Mammals
> >are more closely related to crocs and birds than to snakes and lizards.
>
> He has this right. There doesn't seem to be any doubt that lepidosaurs
> and archosaurs are both sauropsids, whilst mammals are synapsids. There
> is, I believe, a little question about the positions of chelonians, but
> he omitted them from the tree.
> --
> alias Ernest Major

Birds and crocs should branch closer to the synapsid branch point and
not equidistant with snakes and lizards. The figure isn't very good
at making those distinctions, and like I said it is not to scale.

Ron Okimoto

[Ernest Major]

In message
<23c46054-8a8d-40ec...@h10g2000yqn.googlegroups.com>,
chris thompson <chris.li...@gmail.com> writes

There are several cases where we know the ancestral species, Spartina
townsendii and Spartina anglica being one. Cases where we know the
*common* ancestors are not so clear cut - there are cases where several
species have the same ancestry, and cases where one living species is
ancestral to another (i.e. is paraphyletic),

But one example of the first category would be Helianthus anomalus,
Helianthus paradoxus and Helianthus deserticola, which are all
recombinational hybrids of Helianthus annuus and Helianthus petiolaris.

Another would be the three types of triticale, all of which have Secale
cereale as one parent.

A third would be Senecio cambrensis and Senecio eboracensis - the former
is an allohexaploid hybrid of Senecio squalidus and Senecio vulgaris,
and the latter a recombinational tetraploid.
--
alias Ernest Major

[Ernest Major]

In message
<399a372f-5f35-47bc...@v33g2000yqv.googlegroups.com>, Ron
O <roki...@cox.net> writes

As you say, it's not to scale, so it's only the topology (branching
order) that matters.

He has arthropod relationships wrong - insects are deeply nested within
crustaceans.
--
alias Ernest Major

[Robert Carnegie: Fnord: cc talk-origins@moderators.isc.org]

On Saturday, July 7, 2012 9:17:26 PM UTC+1, David wrote:
> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>
> What is a hypothetical common ancestor? Also, do we know the CA for any two species?

Where does the diagram come from?

[John Harshman]

Ron O wrote:
> On Jul 8, 11:59 am, Ernest Major <{$t...@meden.demon.co.uk> wrote:
>> In message
>> <41f52cf2-85fc-4250-871b-0daf3c1d3...@a34g2000yqi.googlegroups.com>, Ron
>> O <rokim...@cox.net> writes
>>
>>> The branch point of crocodiles and birds from reptiles and their
>>> relationship with mammsls seems to be messed up on this figure. Mammals
>>> are more closely related to crocs and birds than to snakes and lizards.
>> He has this right. There doesn't seem to be any doubt that lepidosaurs
>> and archosaurs are both sauropsids, whilst mammals are synapsids. There
>> is, I believe, a little question about the positions of chelonians, but
>> he omitted them from the tree.
>> --
>> alias Ernest Major
>
> Birds and crocs should branch closer to the synapsid branch point and
> not equidistant with snakes and lizards.

Is that tree supposed to be time-calibrated? I don't think so. There's
really nothing wrong with the tree as far as vertebrates go. Ernest is
correct here. You were in error on both counts.

> The figure isn't very good
> at making those distinctions, and like I said it is not to scale.

Nor is it supposed to be. You're accusing a bicycle of not being a very
good flower pot.

[Ray Martinez]

On Jul 8, 4:08 am, John Harshman <jharsh...@pacbell.net> wrote:
> David wrote:
> >http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>
> > What is a hypothetical common ancestor?
>
> Just what it sounds like. Any spot on that tree except the tips of the
> branches is inferred from data, not associated with a known species.
>

For Dana Tweedy: See the word "inferred" in the above sentence?

Please tells us what it means!

LOL!

Ray

[Ron O]

I'm the one that said that it was not scaled to time in the part that
is snipped. I also note that he did get the placenta placement wrong
among the vertebrates so it doesn't seem to be as accurate as you
claim. I was just noting things that didn't look right and have
trouble figuring out what the figure was used for. Fish also came
before jaws. We do still have jawless fish. So it doesn't look too
accurate to me. A lot is missing from the list, but it doesn't have
to have everything. He just needs enough to make his point, whatever
that was.

It is accurate enough if the guy just wanted to talk about nested
characters. A is supposed to represent some hypothetical common
ancestor, possibly, B and C are also hypothetical common ancestors. C
might be the common ancestor of all extant life on earth, or bacteria
may just refer to Archea like fish refers to jawed fish.

Ron Okimoto

[John Harshman]

Ray Martinez wrote:
> On Jul 8, 4:08 am, John Harshman <jharsh...@pacbell.net> wrote:
>> David wrote:
>>> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>>> What is a hypothetical common ancestor?
>> Just what it sounds like. Any spot on that tree except the tips of the
>> branches is inferred from data, not associated with a known species.
>>
>
> For Dana Tweedy: See the word "inferred" in the above sentence?
>
> Please tells us what it means!

Yes, Dana. Tell Ray what it means. Somebody has to, and I'm tired..

[John Harshman]

Nothing wrong with the placenta, just that you need to know it means
"chorio-allantoic placenta"; he is talking about placental mammals,
after all.

> I was just noting things that didn't look right and have
> trouble figuring out what the figure was used for. Fish also came
> before jaws.

Depends on what you mean by "fish". Clearly he means actinopterygians.

> We do still have jawless fish. So it doesn't look too
> accurate to me. A lot is missing from the list, but it doesn't have
> to have everything. He just needs enough to make his point, whatever
> that was.
>
> It is accurate enough if the guy just wanted to talk about nested
> characters. A is supposed to represent some hypothetical common
> ancestor, possibly, B and C are also hypothetical common ancestors.

Every internal node is a hypothetical common ancestor.

> C
> might be the common ancestor of all extant life on earth, or bacteria
> may just refer to Archea like fish refers to jawed fish.

It may be that not all groups are intended to be monophyletic. Lizards,
for example. And "cows" may represent artiodactyls.

[N]

oops!

[Dana Tweedy]

On 7/8/12 3:13 PM, Ray Martinez wrote:
> On Jul 8, 4:08 am, John Harshman<jharsh...@pacbell.net> wrote:
>> David wrote:
>>> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>>
>>> What is a hypothetical common ancestor?
>>
>> Just what it sounds like. Any spot on that tree except the tips of the
>> branches is inferred from data, not associated with a known species.
>>
>
> For Dana Tweedy: See the word "inferred" in the above sentence?
>
> Please tells us what it means!

Very well: According to Mirriam/Webster dictionary:
http://www.merriam-webster.com/dictionary/inferred

Inferred, Infering
transitive verb
1
: to derive as a conclusion from facts or premises <we see smoke and
infer fire — L. A. White> — compare imply
2
: guess, surmise <your letter … allows me to infer that you are as well
as ever — O. W. Holmes †1935>
3
a : to involve as a normal outcome of thought b : to point out :
indicate <this doth infer the zeal I had to see him — Shakespeare>
<another survey…infers that two-thirds of all present computer
installations are not paying for themselves — H. R. Chellman>
4
: suggest, hint <are you inferring I'm incompetent?>



I assume that John is using the term in it's first meaning above.

>
> LOL!

Ray, is there a reason you wanted me to give you this definition, rather
than looking it up for yourself? Do you need help in using a common
dictionary?

BTW, if you had bothered to learn the definition before now, you'd
perhaps not keep making the mistake of claiming that design is not
inferred. May one now expect you'll be using the word correctly, from
now on?


DJT

[Dana Tweedy]

Ray claims to be a "scholar", yet he apparently doesn't know how to use
a common dictionary. Go figure.


DJT

[Ron O]

Marsupials are placental mammals too, just not that type of placental
mammal. The Chorion-allantoic placenta must have been mentioned in
the figure legend that was missing.

>
> > I was just noting things that didn't look right and have
> > trouble figuring out what the figure was used for.  Fish also came
> > before jaws.
>
> Depends on what you mean by "fish". Clearly he means actinopterygians.

Clearly or not?

>
> > We do still have jawless fish.  So it doesn't look too
> > accurate to me.  A lot is missing from the list, but it doesn't have
> > to have everything.  He just needs enough to make his point, whatever
> > that was.
>
> > It is accurate enough if the guy just wanted to talk about nested
> > characters.  A is supposed to represent some hypothetical common
> > ancestor, possibly, B and C are also hypothetical common ancestors.
>
> Every internal node is a hypothetical common ancestor.

But they aren't labeled A, B, and C.

>
> > C
> > might be the common ancestor of all extant life on earth, or bacteria
> > may just refer to Archea like fish refers to jawed fish.
>
> It may be that not all groups are intended to be monophyletic. Lizards,
> for example. And "cows" may represent artiodactyls.

I would expect that, but C could still be either because if bacteria
includes Archea the root of the tree is not correct.

Ron Okimoto

[Harry K]

why don't you look it up? Always expecting someone to do your work
for you.

Harry K

[Ernest Major]

In message <0tadnYLnWKT...@giganews.com>, John Harshman
<jhar...@pacbell.net> writes

The diagram obviously represents selected groups, rather than the whole
tree of life. Given that cows are shown as the sister group to whales,
and whales are (nested in) artiodactyls, it seems likely that cows were
not meant to represent all artiodactyls.
--
alias Ernest Major

[John Harshman]

Unless he's trying also to represent paraphyletic groups. It's highly
inconsistent in its representation, with one taxon as "cows" and another
being "mollusks". It isn't the worst tree I've ever seen. And I ntoice
it does consider the paraphyly of lizards, oddly enough by having
separate taxa for "lizards" and "iquanas".

[Ernest Major]

In message <t9Gdnbljmev...@giganews.com>, John Harshman

<jhar...@pacbell.net> writes
>Ernest Major wrote:
>> In message <0tadnYLnWKT...@giganews.com>, John Harshman
>><jhar...@pacbell.net> writes
>>> Ron O wrote:
>>>> On Jul 8, 3:55 pm, John Harshman <jharsh...@pacbell.net> wrote:
>>>>> Ron O wrote:
>>>>>> On Jul 8, 11:59 am, Ernest Major <{$t...@meden.demon.co.uk> wrote:
>>>>>>> In message
>>>>>>>
>>>>>>><41f52cf2-85fc-4250-871b-0daf3c1d3...@a34g2000yqi.googlegroups.com>, >>>>>>>

>>>>>>> O <rokim...@cox.net> writes
>>>>>>>> The branch point of crocodiles and birds from reptiles and their
>>>>>>>> relationship with mammsls seems to be messed up on this figure.
>>>>>>>>

One opinion is that Iguania (which is more than just iguanas) is the
sister group to other squamates. IMO, it would have been better
labelling lizards as monitor lizards, or varan(o)ids if he didn't mind
going jargony.
--
alias Ernest Major

[Rolf]

Ray Martinez wrote:
> On Jul 8, 4:08 am, John Harshman <jharsh...@pacbell.net> wrote:
>> David wrote:
>>> http://www.debate.org/photos/albums/1/2/1717/38400-1717-d4w3c-a.jpg
>>
>>> What is a hypothetical common ancestor?
>>
>> Just what it sounds like. Any spot on that tree except the tips of
>> the branches is inferred from data, not associated with a known
>> species.
>>
>
> For Dana Tweedy: See the word "inferred" in the above sentence?
>
> Please tells us what it means!
>
> LOL!
>

Says the guy in extacy over the design inference!
A fact-free inference, but good enough for ignorant people not interested in
facts.

[Rolf]

Facts are wasted on creationists.

[Walter Bushell]

In article <qcGVhKWq...@meden.invalid>,
Ernest Major <{$to$}@meden.demon.co.uk> wrote:

> chelonians

We called him a chelonian because he taught us.

--
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