Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 83 (8942 total)
31 online now:
AZPaul3, dwise1, Faith, jar, PaulK, ringo, Tanypteryx, Theodoric (8 members, 23 visitors)
Newest Member: John Sullivan
Post Volume: Total: 863,655 Year: 18,691/19,786 Month: 1,111/1,705 Week: 363/518 Day: 39/88 Hour: 14/9


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Definition of Species
Big_Al35
Member
Posts: 384
Joined: 06-02-2010


Message 181 of 450 (572481)
08-06-2010 6:07 AM
Reply to: Message 179 by caffeine
08-06-2010 5:48 AM


Re: Species Definition
caffeine writes:

As I already pointed out upthread, this isn't true. Evidence of both scavenging and predatory behaviour has been found for tyrannosaurids, which makes sense as most carnivores do both.

Here is a link to show that your claim may be very wrong.


This message is a reply to:
 Message 179 by caffeine, posted 08-06-2010 5:48 AM caffeine has not yet responded

Replies to this message:
 Message 183 by Dr Jack, posted 08-06-2010 6:21 AM Big_Al35 has not yet responded

    
Dr Jack
Member (Idle past 391 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 182 of 450 (572482)
08-06-2010 6:11 AM
Reply to: Message 177 by Big_Al35
08-06-2010 5:20 AM


Re: Species Definition vs what matters (and why)
Your notion that DNA gives a clean, reliable method of determining species is not correct.

This message is a reply to:
 Message 177 by Big_Al35, posted 08-06-2010 5:20 AM Big_Al35 has not yet responded

  
Dr Jack
Member (Idle past 391 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 183 of 450 (572484)
08-06-2010 6:21 AM
Reply to: Message 181 by Big_Al35
08-06-2010 6:07 AM


Re: Species Definition
That would be the evidence of scavenging behaviour...

This message is a reply to:
 Message 181 by Big_Al35, posted 08-06-2010 6:07 AM Big_Al35 has not yet responded

  
Wounded King
Member (Idle past 2381 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 184 of 450 (572485)
08-06-2010 6:27 AM
Reply to: Message 177 by Big_Al35
08-06-2010 5:20 AM


Re: Species Definition vs what matters (and why)
Lions and tigers could be classed as the same species as they can interbreed and produce fertile female offspring. They could be classed as different species as they have different behaviour, appearance and environment. The only way to clearly identify the distinctions is to investigate the DNA.

How on earth do you think DNA will do this at all? DNA won't magically turn the arbitrary definitions of species into something clear cut and well defined, it will just give us another set of criteria for a further arbitrary definition.

The idea that simply sequencing a genome will somehow reveal to you information about a species' behaviour or appearance, that you haven't already discerned by actually studying the species is ludicrous. Even in something as seemingly straight forward as coat colour there are many genes involved, there is no one gene for coat colour.

Maybe decades down the line we will have a wide enough and detailed enough library of genomic data that we could make such predictions when given a novel genome, but for most complex traits I would be doubtful if it will even be that soon.

I ceratinly don't think we will be able to take an unknown genome and from it extrapolate the morphology, behavior and other biological minutiae of the organism.

We can certainly produce high quality phylogenetic trees from the levels of families (as in mother, father and offspring) up to between the various different kingdoms of life. But this still doesn't tell us where to demarcate the boundaries for a species. In some cases it would probably be fairly straight forward, a cluster analysis based on a wide sample of commonly conserved genes would certainly separate out humans from chimps from gorilla.

The question is how we define a species when you have several much more closely related populations, in the same way that there is more of a problem with distinguishing on the basis of morpholgoy as species becomes more similar. Once again it comes down to being lumpers or splitters, what criteria do we use to define a phylogenetic species? Set the criteria too tightly and suddenly you have ten new species of tiger, for example, too loose and suddenly all of the Panthera become 1 species.

The problem here is not one of best guesses but, as has been suggested, of the fact that the whole idea of species is an arbitrary human construct imposed on the natural world.

TTFN,

WK


This message is a reply to:
 Message 177 by Big_Al35, posted 08-06-2010 5:20 AM Big_Al35 has responded

Replies to this message:
 Message 186 by Big_Al35, posted 08-06-2010 6:58 AM Wounded King has responded

    
Percy
Member
Posts: 18872
From: New Hampshire
Joined: 12-23-2000
Member Rating: 2.5


Message 185 of 450 (572487)
08-06-2010 6:39 AM
Reply to: Message 180 by Big_Al35
08-06-2010 5:59 AM


Re: Species Definition
Big_Al35 writes:

Here is a link to show that others don't share your view.

Here is a forum guideline that shows how to use links:

  1. Bare links with no supporting discussion should be avoided. Make the argument in your own words and use links as supporting references.

--Percy


This message is a reply to:
 Message 180 by Big_Al35, posted 08-06-2010 5:59 AM Big_Al35 has not yet responded

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


Message 186 of 450 (572489)
08-06-2010 6:58 AM
Reply to: Message 184 by Wounded King
08-06-2010 6:27 AM


Re: Species Definition vs what matters (and why)
Wounded King writes:

The problem here is not one of best guesses but, as has been suggested, of the fact that the whole idea of species is an arbitrary human construct imposed on the natural world.

This would depend on whether you believe in ID or not. Either it's a human construct or a divine construct. Our model is ofcourse the human understanding of it.

If we were talking about software we could be arguing about what makes word word and not excel. Then we would have to discuss why excel is different from lotus 123 or supercalc. Are they the same type/class? Did office 2000 evolve from office 1997. Do word and excel have a common ancestor? Answers on a postcard please.


This message is a reply to:
 Message 184 by Wounded King, posted 08-06-2010 6:27 AM Wounded King has responded

Replies to this message:
 Message 188 by Wounded King, posted 08-06-2010 7:15 AM Big_Al35 has responded

    
Wounded King
Member (Idle past 2381 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 187 of 450 (572490)
08-06-2010 7:10 AM
Reply to: Message 180 by Big_Al35
08-06-2010 5:59 AM


Re: Species Definition
I think you are going to have to stop posting essentially bare links, especially since they rarely if ever back up your claims.

I can't find anywhere in that interview where Johanson states that Lucy represents a common ancestor for any modern species. The closest I can find is him saying 'We are beginning to look for discoveries that will shed some light on the beginnings of the lineage of Homo, which ultimately gave rise to us, Homo sapiens.' which doesn't say anything about Lucy.

The only other thing I can find is the magaziens own preamble which says, 'At the time she was found, Lucy was our oldest-known human ancestor by more than a million years. '

Which is still very far from saying Lucy is the common ancestor for any modern species.

TTFN,

WK


This message is a reply to:
 Message 180 by Big_Al35, posted 08-06-2010 5:59 AM Big_Al35 has not yet responded

    
Wounded King
Member (Idle past 2381 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 188 of 450 (572491)
08-06-2010 7:15 AM
Reply to: Message 186 by Big_Al35
08-06-2010 6:58 AM


Re: Species Definition vs what matters (and why)
This would depend on whether you believe in ID or not.

Is this another case of creationism hiding in ID's clothing? I can understand a creationist 'created kinds' approach being in line with what you say, but as far as I can tell it has nothing to do with actual Intelligent Design arguments.

And none of this addresses the fact that since god didn't leave an FAQ behind about discerning kinds through genetics, the way to do so is far from obvious if indeed such a thing exists.

TTFN,

WK


This message is a reply to:
 Message 186 by Big_Al35, posted 08-06-2010 6:58 AM Big_Al35 has responded

Replies to this message:
 Message 189 by Big_Al35, posted 08-06-2010 8:48 AM Wounded King has responded

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


Message 189 of 450 (572513)
08-06-2010 8:48 AM
Reply to: Message 188 by Wounded King
08-06-2010 7:15 AM


Re: Species Definition vs what matters (and why)
Wounded King writes:

And none of this addresses the fact that since god didn't leave an FAQ behind about discerning kinds through genetics, the way to do so is far from obvious if indeed such a thing exists.

There are plenty of sites showing that DNA barcoding is well underway. Here is a link which shows that some mammals have already been barcoded, and that this is a very effective tool for species identification. I think it's just a matter of time before this becomes the standard. It's not about what I want....it's happening.

Edited by Big_Al35, : No reason given.


This message is a reply to:
 Message 188 by Wounded King, posted 08-06-2010 7:15 AM Wounded King has responded

Replies to this message:
 Message 190 by Percy, posted 08-06-2010 9:17 AM Big_Al35 has responded
 Message 191 by Wounded King, posted 08-06-2010 9:25 AM Big_Al35 has not yet responded

    
Percy
Member
Posts: 18872
From: New Hampshire
Joined: 12-23-2000
Member Rating: 2.5


Message 190 of 450 (572514)
08-06-2010 9:17 AM
Reply to: Message 189 by Big_Al35
08-06-2010 8:48 AM


Re: Species Definition vs what matters (and why)
Big_Al35 writes:

There are plenty of sites showing that DNA barcoding is well underway. Here is a link which shows that some mammals have already been barcoded, and that this is a very effective tool for species identification. I think it's just a matter of time before this becomes the standard. It's not about what I want....it's happening.

You're just not getting what WK is saying, so let's go back to the example I mentioned earlier about African elements. Remember I said that there's a debate about how African elephants should be divided into separate species? Before barcodes for African elephants can be used, decisions must be made about what those species are and how various DNA signposts break down into the different species. These decisions about barcodes are all made by people. Species divisions are a human construct, not a fact inherent in nature.

Some species have little variation and no near relatives making classification as a species an easy task. Other species have a great deal of variation and many near relatives. In such case how does one divide one species from another? Are they different species if they *can* interbreed but don't? Are they different species if they *do* interbreed, but only 0.001% of the time? How about 0.01% of the time? How about 0.1% of the time? 1%? 10%? These decision are all made by people.

Across all the variation of a species, are the different varieties just races within the species, or are they perhaps different species? Within a race is the variation subraces or not? These decisions are all made by people.

Your objections all share something in common: they're all based upon misconstruals.

--Percy


This message is a reply to:
 Message 189 by Big_Al35, posted 08-06-2010 8:48 AM Big_Al35 has responded

Replies to this message:
 Message 192 by Big_Al35, posted 08-06-2010 9:37 AM Percy has responded

    
Wounded King
Member (Idle past 2381 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 191 of 450 (572515)
08-06-2010 9:25 AM
Reply to: Message 189 by Big_Al35
08-06-2010 8:48 AM


Re: Species Definition vs what matters (and why)
And in what way is genetic barcoding not still just based around arbitrary species definitions? Simply choosing the Cytochrome Oxidase 1 as the arbiter of all species classification seems nothing but arbitray to me.

TTFN,

WK


This message is a reply to:
 Message 189 by Big_Al35, posted 08-06-2010 8:48 AM Big_Al35 has not yet responded

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


Message 192 of 450 (572518)
08-06-2010 9:37 AM
Reply to: Message 190 by Percy
08-06-2010 9:17 AM


Re: Species Definition vs what matters (and why)
Percy writes:

Your objections all share something in common: they're all based upon misconstruals.

Objections!?! I don't think I have raised any objections as such....I don't disagree that locking down a species to a barcode will be an arbitrary human decision. I am confident we can get better at this over time though. These barcodes don't have to be set in stone either. Lets take the African elephant example. If the DNA barcoding was defined such that two African elephants ended up being different species I think we can rest assured that our system needs adjusting. Now if our system showed that African elephants were a different species to an Asian elephant then that would be a matter for debate.

If you are saying that experts in the field are actively advocating that Ugandan elephants are distinguished from Zambian elephants and they want them classified as different species I don't have any objection with that as such. Once the system is established and in place we can stick with it.

If anomalies rise in the future we can deal with those on an individual basis. Ofcourse there is no room for history in any of this. The fossil records and extinct animals are not part of this discussion.


This message is a reply to:
 Message 190 by Percy, posted 08-06-2010 9:17 AM Percy has responded

Replies to this message:
 Message 193 by Huntard, posted 08-06-2010 9:43 AM Big_Al35 has responded
 Message 195 by Percy, posted 08-06-2010 10:54 AM Big_Al35 has responded

    
Huntard
Member (Idle past 582 days)
Posts: 2870
From: Limburg, The Netherlands
Joined: 09-02-2008


Message 193 of 450 (572520)
08-06-2010 9:43 AM
Reply to: Message 192 by Big_Al35
08-06-2010 9:37 AM


Re: Species Definition vs what matters (and why)
Big_Al35 writes:

If the DNA barcoding was defined such that two African elephants ended up being different species I think we can rest assured that our system needs adjusting.


But how would you determine that with DNA? It's not like there's gonna be a clear point at which you can say: "Aha! if it has these genes, it must be a different species!". That is arbitrarily determined by men, if it is determined at all.

Now if our system showed that African elephants were a different species to an Asian elephant then that would be a matter for debate

Why? Since they are already accepted as different species.

If you are saying that experts in the field are actively advocating that Ugandan elephants are distinguished from Zambian elephants and they want them classified as different species I don't have any objection with that as such. Once the system is established and in place we can stick with it.

But we already have a system in place, why change it?

This message is a reply to:
 Message 192 by Big_Al35, posted 08-06-2010 9:37 AM Big_Al35 has responded

Replies to this message:
 Message 194 by Big_Al35, posted 08-06-2010 10:16 AM Huntard has not yet responded

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


Message 194 of 450 (572525)
08-06-2010 10:16 AM
Reply to: Message 193 by Huntard
08-06-2010 9:43 AM


Re: Species Definition vs what matters (and why)
Huntard writes:

But we already have a system in place, why change it?

This is what my mum says to me when I tell her to switch to online shopping.


This message is a reply to:
 Message 193 by Huntard, posted 08-06-2010 9:43 AM Huntard has not yet responded

    
Percy
Member
Posts: 18872
From: New Hampshire
Joined: 12-23-2000
Member Rating: 2.5


Message 195 of 450 (572531)
08-06-2010 10:54 AM
Reply to: Message 192 by Big_Al35
08-06-2010 9:37 AM


Re: Species Definition vs what matters (and why)
Percy writes:

Your objections all share something in common: they're all based upon misconstruals.

Big_Al35 writes:

Objections!?! I don't think I have raised any objections as such...

Really? What about this misconstrual of how much we know about T-Rex:

Big_Al35 in Message 160 writes:

TRex is a mystery. All we have are movie images and directors imaginations to go on. If you found two TRex half skeletons I think you would be hard pushed to even show that it was the same animal. You would have no idea if they could interbreed and their behaviour is unknown.

And what about this misconstrual of DNA's power to determine species boundaries:

Big_Al_35 in Message 177 writes:

I think it's fair to say that species cannot be determined unless you know their DNA.

And what about this objection based upon a misconstrual about scientists claims of finding common ancestors based upon an article you linked to:

Big_Al35 in Message 180 writes:

Here is a link to show that others don't share your view.

And here's you doing the exact same thing again, misconstruing yet another article you linked to about possible scavenging behavior in T-Rex:

Big_Al35 in Message 181 writes:

Here is a link to show that your claim may be very wrong.

Moving on:

Now if our system showed that African elephants were a different species to an Asian elephant then that would be a matter for debate.

Either you misspoke or you're hopelessly confused. While there is debate about how African elephants might break down into different species, there's no disagreement that African and Asian elephants are different species.

By the way, that was you registering yet another objection, right? Just making sure.

If you are saying that experts in the field are actively advocating that Ugandan elephants are distinguished from Zambian elephants and they want them classified as different species I don't have any objection with that as such. Once the system is established and in place we can stick with it.

Species classifications aren't facts of nature like the mass of an electron or the speed of light. They're human constructs. There can never be any gradually homing in on more and more accurate answers because while increasing knowledge always helps the human factor is overwhelming in this case. The very criteria themselves for determining species will change over time. There are probably tons of biologists who don't even take classification that seriously, since it's the actual details that are important and that get lost in broad classification systems.

--Percy


This message is a reply to:
 Message 192 by Big_Al35, posted 08-06-2010 9:37 AM Big_Al35 has responded

Replies to this message:
 Message 196 by Big_Al35, posted 08-06-2010 11:21 AM Percy has acknowledged this reply

    
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019