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Author Topic:   Definition of Species
Huntard
Member (Idle past 405 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 121 of 450 (570425)
07-27-2010 11:29 AM
Reply to: Message 120 by Big_Al35
07-27-2010 10:48 AM


Re: Not even tangential to the original direction.
Big_Al35 writes:

So there might be a living common ancestor for fish and monkeys right?


Not likely. It would be an ancestor of modern fish, in any case.

Can't we track this down?

How much do you think that will cost? And finding an ancestor to modern fish isn't really what we need, we've got those already.

DNA evidence should do the trick.

DNA evidence points to the fact that the common ancestor of modern fish and monkeys was an ancestor of the modern fish.

You see, modern fish aren't related to monkeys as monkeys are related to say, apes. There are many more steps to get from a fish to a monkey, then from a monkey to an ape. In fact, (and guys more knowledgeable than me would need to confirm this), I feel pretty confident to say that no fish species alive today is descendant from the same branch of the tree of life that brought us monkeys. But like I said, I could have this wrong.


This message is a reply to:
 Message 120 by Big_Al35, posted 07-27-2010 10:48 AM Big_Al35 has responded

Replies to this message:
 Message 124 by Big_Al35, posted 07-28-2010 6:11 AM Huntard has responded

    
Wounded King
Member (Idle past 2204 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 122 of 450 (570426)
07-27-2010 11:30 AM
Reply to: Message 120 by Big_Al35
07-27-2010 10:48 AM


Re: Not even tangential to the original direction.
Can't we track this down? DNA evidence should do the trick.

Probably not hence my use of the term 'morphospecies', which is a species classification base solely on morphology. Even if we could identify a fossil as a definitive latest common ancestor and find an identical extant morphospecies there would no way we could know how much genetic distance separated the two. That isn't to say that such a species wouldn't be interesting in terms of comparative developmental genetics, just that we wouldn't be able to have any confidence that its genome was the same as that of the LCA of monkeys and modern fish.

As an example the Burgess Shale fossil Pikaia is often suggested as an example of the sort of primitive chordate that modern vertebrates may have descended from, this doesn't mean that anyone is claiming that the morphologically similar currently extant Lancelet is the latest common ancestor of all vertebrates.

TTFN,

WK


This message is a reply to:
 Message 120 by Big_Al35, posted 07-27-2010 10:48 AM Big_Al35 has not yet responded

    
Blue Jay
Member (Idle past 807 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 123 of 450 (570487)
07-27-2010 3:23 PM
Reply to: Message 104 by Big_Al35
07-27-2010 6:45 AM


Re: Complexity of an organism
Hi, Big Al.

Big_Al35 writes:

However, when I suggest that a fish might have evolved from a monkey you baulk at this idea.

What I am about to write is pretty much what everyone else has already written, but, the more bullets we shoot, the more chance we have of hitting the target.

I have no objections to the hypothetical possibility that fish could have hypothetically evolved from monkeys.

It is not an objection based on ideology: it is an objection based on evidence.

The evidence includes ancient fish predating monkeys, and a series of fossils that arrange chronologically in the fossil record, such that the progressively more monkey-like organisms in the sequence are found after the less monkey-like organisms in the sequence.

Therefore, I do have objections to the possibility that fish actually did evolve from monkeys.

-----

Big_Al35 writes:

Now if you suggested that a complex creature could evolve into a simpler creature where its very survival depended on it I might understand this. However, if I gave any example of this you would no doubt claim I was raving mad.

I’ll save you the trouble. Pentastomids (also called “tongue worms”) are most often thought of as “degenerate” crustaceans (i.e. crustaceans who have become less complex than their ancestors).

Another example is the Order Strepsiptera (also called “twisted-wing parasites”), in which the females have lost, over evolutionary time, their wings, their legs, their eyes, etc., and resemble maggots.

I would not have considered you raving mad for pointing out either of these examples. To the contrary, I would have considered you well-read and observant.

As it stands, I still don’t think you’re raving mad: but, I do suspect that you are not exercising sufficient care in constructing your arguments, and that you view yourself as more knowledgeable than you actually are.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
 Message 104 by Big_Al35, posted 07-27-2010 6:45 AM Big_Al35 has not yet responded

  
Big_Al35
Member
Posts: 384
Joined: 06-02-2010


Message 124 of 450 (570659)
07-28-2010 6:11 AM
Reply to: Message 121 by Huntard
07-27-2010 11:29 AM


Re: Not even tangential to the original direction.
So there might be a living common ancestor for fish and monkeys right?

Huntard writes:

Not likely. It would be an ancestor of modern fish, in any case.

Ok...so the ancestor for a modern fish is just another fish by anyones understanding.
And the ancestor of a monkey is a fish based on the arguments here.
So if we found the common ancestor we could probably just assume that it was infact only the ancestor for a fish. I am guessing that there must be thousands or millions of pieces of evidence showing that the ancestors of fish were infact fish.

Would I be wrong in thinking that we couldn't actually deduce anything from this at all?


This message is a reply to:
 Message 121 by Huntard, posted 07-27-2010 11:29 AM Huntard has responded

Replies to this message:
 Message 125 by caffeine, posted 07-28-2010 6:51 AM Big_Al35 has responded
 Message 126 by Huntard, posted 07-28-2010 7:46 AM Big_Al35 has not yet responded

    
caffeine
Member
Posts: 1624
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.6


Message 125 of 450 (570662)
07-28-2010 6:51 AM
Reply to: Message 124 by Big_Al35
07-28-2010 6:11 AM


Re: Not even tangential to the original direction.
So if we found the common ancestor we could probably just assume that it was infact only the ancestor for a fish.

Why would you assume this? We know from DNA evidence, and from morphological similarities, that some fish are more closely related to land animals than they are to other fish. So, if we found the common ancestor of all fish, we'd know that it was also the ancestor of land vertrebrates.


This message is a reply to:
 Message 124 by Big_Al35, posted 07-28-2010 6:11 AM Big_Al35 has responded

Replies to this message:
 Message 127 by Big_Al35, posted 07-28-2010 9:19 AM caffeine has responded

  
Huntard
Member (Idle past 405 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 126 of 450 (570663)
07-28-2010 7:46 AM
Reply to: Message 124 by Big_Al35
07-28-2010 6:11 AM


Re: Not even tangential to the original direction.
Big_Al35 writes:

Ok...so the ancestor for a modern fish is just another fish by anyones understanding.


Yes.

And the ancestor of a monkey is a fish based on the arguments here.

Not directly, there are more intermediate stages, amfibians and reptiles, for example.

So if we found the common ancestor we could probably just assume that it was infact only the ancestor for a fish.

No, since Fish eventually evolved into monkeys, therefore the ancestor of all fish is also the ancestor to all monkeys. It's therefore their common ancestor.

I am guessing that there must be thousands or millions of pieces of evidence showing that the ancestors of fish were infact fish.

Well, we have fossil fish, so yes.

Would I be wrong in thinking that we couldn't actually deduce anything from this at all?

Yes, you would be wrong.

I'll try to visualize it for you.

As you can see, the common abcestor for all modern fish and monkeys is a fish. This is what you asked for. Keep in mind though that this is a very very very simplistic representation, I left out a lot of intermediate forms everywhere.

Edited by Huntard, : Changed a bit for clarity


This message is a reply to:
 Message 124 by Big_Al35, posted 07-28-2010 6:11 AM Big_Al35 has not yet responded

    
Big_Al35
Member
Posts: 384
Joined: 06-02-2010


Message 127 of 450 (570671)
07-28-2010 9:19 AM
Reply to: Message 125 by caffeine
07-28-2010 6:51 AM


Re: Not even tangential to the original direction.
caffeine writes:

Why would you assume this? We know from DNA evidence, and from morphological similarities, that some fish are more closely related to land animals than they are to other fish. So, if we found the common ancestor of all fish, we'd know that it was also the ancestor of land vertrebrates.

That's the whole point though. We DON'T have access to ancestral DNA so we can't deduce what you have deduced above.
If you are suggesting that it would make more sense to assume that an ancestral fish was a direct ancestor of say a rabbit I could equally ask you why you have assumed this.

My point is that an ancestral fish was a fish and will have DNA to match this. It will also be more closely related to a modern fish than say a rabbit in terms of its DNA. So it would be safe to assume that an ancient fish was an ancestor of the modern fish.

Now, if you are suggesting that the DNA of some modern fish is more closely related to a rabbits than it is to other fish then dare I say it.....fishy pun.....this would be a red herring. Because these fish are NOT the ancestors of rabbits. They are infact modern fish.

Ofcourse, all of this is indeterminate without the ancestral DNA.


This message is a reply to:
 Message 125 by caffeine, posted 07-28-2010 6:51 AM caffeine has responded

Replies to this message:
 Message 128 by jar, posted 07-28-2010 9:43 AM Big_Al35 has not yet responded
 Message 129 by caffeine, posted 07-28-2010 10:07 AM Big_Al35 has responded
 Message 130 by crashfrog, posted 07-28-2010 2:11 PM Big_Al35 has not yet responded

    
jar
Member
Posts: 30936
From: Texas!!
Joined: 04-20-2004


Message 128 of 450 (570680)
07-28-2010 9:43 AM
Reply to: Message 127 by Big_Al35
07-28-2010 9:19 AM


Re: Not even tangential to the original direction.
Big_Al35 writes:

That's the whole point though. We DON'T have access to ancestral DNA so we can't deduce what you have deduced above.

Excuse me? Why can't we assume that with a very high degree of confidence in fact?


Anyone so limited that they can only spell a word one way is severely handicapped!
This message is a reply to:
 Message 127 by Big_Al35, posted 07-28-2010 9:19 AM Big_Al35 has not yet responded

  
caffeine
Member
Posts: 1624
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 5.6


(1)
Message 129 of 450 (570687)
07-28-2010 10:07 AM
Reply to: Message 127 by Big_Al35
07-28-2010 9:19 AM


Re: Not even tangential to the original direction.
quote:
the whole point though. We DON'T have access to ancestral DNA so we can't deduce what you have deduced above.

We don’t have access to the ancestral DNA, no, but we do have access to the DNA of living animals, and this is how the family trees of life are constructed (or, more accurately, how they are refined). Let’s say we have three animals – A, B and C – and we look at their genomes. The genomes of A and B turn out to be much more similar to each other than either is to the genome of C. We assume, then, that A and B share a common ancestor with each other more recently than either does with C. If A and B shared a common ancestor more recently than A and C, then A and B's genome should be more similar, having had less time to diverge from each other. Now imagine that A is a rabbit, B is a lungfish and C is a tuna, and you see why the tree of life is constructed as it is.

It's not just genetic evidence, by the way. Lungfish and coelacanths were grouped with land vertebrates long before there was DNA evidence for it, based on morphological evidence.

quote:
My point is that an ancestral fish was a fish and will have DNA to match this. It will also be more closely related to a modern fish than say a rabbit in terms of its DNA. So it would be safe to assume that an ancient fish was an ancestor of the modern fish.

The ancient fish will probably not have DNA significantly more similar to the modern fish than to rabbits. The DNA of fish has gone through hundreds of millions of years of mutations - just like those of rabbits, and the fish wouldn't be very much alike. The DNA of different fish is very different - a noted above, lungfish are more genetically similar to monkeys than to tuna, while tuna are more genetically similar to elephants than to sharks.

quote:
Now, if you are suggesting that the DNA of some modern fish is more closely related to a rabbits than it is to other fish then dare I say it.....fishy pun.....this would be a red herring. Because these fish are NOT the ancestors of rabbits. They are infact modern fish.

I'm not sure why you think this is relevant. The significant fact about these fish being lumped in with rabbits and monkey's genetically is that their ancestors diverged from those of other fish before they diverged from land vertebrates. This means that the common ancestor of all fish is also an ancestor of land vertebrates. So, even without any fossil evidence, we'd assume that land vertebrates eventually trace their ancestry to fish. This is the simpler explanation, because it just requires a creature that looks like a fish, one of whose descendent lines lost thi distincitve fishiness to become tetrapods. The other possibility, that the common ancestor was not a fish, would require the distinctive features of fishiness to have arisen at least three times independently in different lineages of fish ancestors. Monkeys evolving from fish is the simpler explanation (and, once fossil evidence is taken into account, the only sensible explanation).


This message is a reply to:
 Message 127 by Big_Al35, posted 07-28-2010 9:19 AM Big_Al35 has responded

Replies to this message:
 Message 132 by Big_Al35, posted 07-29-2010 7:27 AM caffeine has not yet responded

  
crashfrog
Inactive Member


Message 130 of 450 (570736)
07-28-2010 2:11 PM
Reply to: Message 127 by Big_Al35
07-28-2010 9:19 AM


Re: Not even tangential to the original direction.
We DON'T have access to ancestral DNA so we can't deduce what you have deduced above.

We have access to it because they passed it along to their descendants when they reproduced.

So it would be safe to assume that an ancient fish was an ancestor of the modern fish.

And then the ancestor of that ancient fish would be something that was not a fish, some finless marine chordate perhaps.


This message is a reply to:
 Message 127 by Big_Al35, posted 07-28-2010 9:19 AM Big_Al35 has not yet responded

  
RAZD
Member
Posts: 19819
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 10.0


Message 131 of 450 (570824)
07-29-2010 12:12 AM


TOPIC
The last 50+ posts have nothing to do with the definition of species.

See Message 87 onward (in a downward spriral)


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

  
Big_Al35
Member
Posts: 384
Joined: 06-02-2010


Message 132 of 450 (570850)
07-29-2010 7:27 AM
Reply to: Message 129 by caffeine
07-28-2010 10:07 AM


Re: Not even tangential to the original direction.
caffeine writes:

The genomes of A and B turn out to be much more similar to each other than either is to the genome of C. We assume, then, that A and B share a common ancestor

Why would you assume this? Does this sound familiar?

Let's consider three creatures A, B and C where A is the parent of B and C and all of these creatures are fish. Imagine that C's lineage produces a rabbit and B's lineage on the other hand remains a fish. Furthermore lets imagine that A, B and C share some genes X, Y and Z that are not found amongst other fish. Now imagine that those genes appear in all rabbits. Your assumption is that the B's lineage should be lumped together with a rabbits. This is a false assertion as the genes X,Y and Z clearly don't define a species of rabbit nor do they define a species of fish. They are irrelevant genes because a fish with X,Y,Z genes will not evolve into a rabbit as evidenced by B's lineage. Similarly a rabbit with X,Y,Z will never evolve into a fish as evidenced by the fact that rabbits always give birth to rabbits.

So there must be some other genes say P,Q,R which actually make a rabbit a rabbit. The P,Q and R genes will only appear in rabbit and never in a fish. If they did appear in a fish the fish would become a rabbit. These genes have effectively appeared by magic. These genes are proof that the rabbit could not have a fish ancestor as no fish have this sequence.

Go figure....


This message is a reply to:
 Message 129 by caffeine, posted 07-28-2010 10:07 AM caffeine has not yet responded

Replies to this message:
 Message 133 by Huntard, posted 07-29-2010 8:19 AM Big_Al35 has responded

    
Huntard
Member (Idle past 405 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 133 of 450 (570855)
07-29-2010 8:19 AM
Reply to: Message 132 by Big_Al35
07-29-2010 7:27 AM


Re: Not even tangential to the original direction.
Big_Al35 writes:

Let's consider three creatures A, B and C where A is the parent of B and C and all of these creatures are fish.


Ok.

Imagine that C's lineage produces a rabbit and B's lineage on the other hand remains a fish.

Ok.

Furthermore lets imagine that A, B and C share some genes X, Y and Z that are not found amongst other fish.

Ok.

Now imagine that those genes appear in all rabbits.

Ok.

Your assumption is that the B's lineage should be lumped together with a rabbits.

No. We should say that all rabits and everything that B produces shares a common ancestor, A, which it does, according to your example.

This is a false assertion as the genes X,Y and Z clearly don't define a species of rabbit nor do they define a species of fish.

So?

They are irrelevant genes because a fish with X,Y,Z genes will not evolve into a rabbit as evidenced by B's lineage.

It can, you said so yourself, remember? C turns into a rabbit, and C was a fish.

Similarly a rabbit with X,Y,Z will never evolve into a fish as evidenced by the fact that rabbits always give birth to rabbits.

Nobody said a rabbit evolved into a fish. This statement is irrelevant to your example. It's also wrong, if rabits gave birth to something other than rabits it would falsify ToE.

So there must be some other genes say P,Q,R which actually make a rabbit a rabbit.

Yes. So?

The P,Q and R genes will only appear in rabbit and never in a fish.

It's your example, so sure.

If they did appear in a fish the fish would become a rabbit.

Again, if you say so.

These genes have effectively appeared by magic.

Well, it's your example, so you're free to let them appear by magic. In nature though, they would appear through mutations.

These genes are proof that the rabbit could not have a fish ancestor as no fish have this sequence.

No they're not.

Go figure....

That you not only contraddicted yourself, but also your logic is wrong? I just did.
This message is a reply to:
 Message 132 by Big_Al35, posted 07-29-2010 7:27 AM Big_Al35 has responded

Replies to this message:
 Message 134 by Big_Al35, posted 07-29-2010 8:52 AM Huntard has responded

    
Big_Al35
Member
Posts: 384
Joined: 06-02-2010


Message 134 of 450 (570858)
07-29-2010 8:52 AM
Reply to: Message 133 by Huntard
07-29-2010 8:19 AM


Re: Not even tangential to the original direction.
Huntard writes:

Well, it's your example, so you're free to let them appear by magic. In nature though, they would appear through mutations.

Mutations have nothing to do with natural selection or survival of the fittest...which is what I am talking about.

If you have another theory of evolution please be sure to share that with us.


This message is a reply to:
 Message 133 by Huntard, posted 07-29-2010 8:19 AM Huntard has responded

Replies to this message:
 Message 135 by Huntard, posted 07-29-2010 9:02 AM Big_Al35 has responded

    
Huntard
Member (Idle past 405 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 135 of 450 (570861)
07-29-2010 9:02 AM
Reply to: Message 134 by Big_Al35
07-29-2010 8:52 AM


Re: Not even tangential to the original direction.
Big_Al35 writes:

Mutations have nothing to do with natural selection or survival of the fittest...which is what I am talking about.


No you weren't. You were talking about the appearance of "new genes" in your species C. New genes appear through mutations, natural selection is the thing that determines if they get to propogate or not.

If you have another theory of evolution please be sure to share that with us.

I don't. Mutations are part of the current ToE.
This message is a reply to:
 Message 134 by Big_Al35, posted 07-29-2010 8:52 AM Big_Al35 has responded

Replies to this message:
 Message 136 by Big_Al35, posted 07-29-2010 9:27 AM Huntard has responded

    
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