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Author Topic:   Is Earth old enough for DNA to evolve?
PaulK
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Joined: 01-10-2003
Member Rating: 2.5


(1)
Message 31 of 60 (668153)
07-17-2012 6:29 PM
Reply to: Message 11 by bcoop
07-17-2012 9:18 AM


Re: I stand corrected
quote:

again - these things are difficult to articulate - especially knowing the level of people that are reading this

It isn't difficult to realise that proposing a generation time of 20 years is grossly unrealistic. Anyone familiar with the breeding rates of animals would know that much.

quote:

However, it was probably a child that said the king had no clothes on. I believe that asking the question how long did it take to generate the human genome is a legitimate one, and I am not really seeing a lot of answers to that so far.

It is also wise to know your limits. Trying to propose an answer to the question - as you did - without a sound basis for doing so is different from asking the question. And it is that piece of folly that has attracted criticism.

It is all very well to say that the math has to work - but the main reason why your math didn't work is because you didn't have a sensible (or even coherent) model OR sensible values for the parameters.

Now I am not going to propose a model because that is beyond my expertise. But I hope that my posts have at least demonstrated that the issue is far more complex than you thought.


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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 32 of 60 (668160)
07-17-2012 8:34 PM
Reply to: Message 27 by New Cat's Eye
07-17-2012 12:16 PM


Re: Generation lengths bogus
I need to print this out and study it - there is a lot on there - I wonder if we are in the midst of another mass extinction?
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Dr Adequate
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Posts: 15476
Joined: 07-20-2006
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Message 33 of 60 (668162)
07-17-2012 8:41 PM
Reply to: Message 9 by bcoop
07-17-2012 9:09 AM


Re: Not so fast
I appreciate your detailed reply. The attempt here was to really ask the question:
“Has mathematical modeling been conducted of the amount of time it would take to generate the human genome”?
Yes, my simplistic model is full of errors, which you correctly point out, but you do not really address the underlying question, which is has someone modeled this process over time.

Well, you didn't actually ask the "underlying question", which is why I didn't address it.

Some calculations have been done. For example, you mention the eye: you might want to look at Nilsson and Pelger's paper: "A pessimistic estimate of the time required for an eye to evolve".

I'm not sure that anyone's tried to make an estimate of how long the whole thing would take. I think if anyone tried,they'd have to make so many guesses that by the time they'd added up all the vagueness they'd be lucky to get within a couple of orders of magnitude; whereas using radiometric dating you actually get the right answer.

Yes – a yeast cell may reproduce in 90 minutes but how long does it take for a positive change to end up in the human DNA on the the end of the chain where we are now, taking into account natural selection and the host of other factors?

But you have to take into account the generation time, is my point. Which is just one of the things you'd have to guess at. If you look at (for example) one-celled eukaryotes, you get quite a wide spread of generation times, depending on species and environment. Then we might ask ourselves how this would apply to primitive one-celled eukaryotes. It would not be unreasonable to speculate that the earliest, crudest versions took ten or even a hundred times longer to reproduce than the modern versions. And then you've got two orders of magnitude of potential error right there.

The point about Deleterious mutations was only that it would add more time to the process to overcome them.

And I pointed out why it wouldn't.

As far as your comments about reading a textbook, I did know that there were other methods that increase the length of the genome, but I was writing a one paragraph model of a concept I wanted to discuss.

Well, you sounded more sure of yourself then than you do now.

Your criticism is a little harsh, and maybe a little bit knee jerk to my post.

I thought I was being tactful. This is admittedly something I'm not good at.


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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 34 of 60 (668163)
07-17-2012 8:44 PM
Reply to: Message 29 by Tangle
07-17-2012 4:08 PM


Is there any idea why this would be? I dare not speculate.
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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 35 of 60 (668164)
07-17-2012 8:46 PM
Reply to: Message 30 by Taq
07-17-2012 5:47 PM


Re: Not so fast
Not only fascinating, but apparently you are working in the middle of it! It would be interesting to read some posts on where you guys think it is headed and what the implications are.
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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 36 of 60 (668167)
07-17-2012 8:57 PM
Reply to: Message 31 by PaulK
07-17-2012 6:29 PM


Re: I stand corrected
I appreciate your comments and have taken them to heart.
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Dr Adequate
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Posts: 15476
Joined: 07-20-2006
Member Rating: 4.0


Message 37 of 60 (668168)
07-17-2012 8:57 PM
Reply to: Message 34 by bcoop
07-17-2012 8:44 PM


Wikipedia says it's "an octoploid and suspected allopolyploid hybrid of four species". So its genome has been duplicated twice, and also is made up of the genomes of several different species of plants which have bred together by a weird genetic accident, each donating its entire genome to the mix rather than half each as in normal reproduction.

It's stuff like this that, again, makes it hard to figure out how long the evolution of something ought to take --- because we couldn't figure out a priori that this stuff would happen on the way to Paris japonica, we have to look after the fact and note that it did.

In the same way, it's perfectly possible that one of the things that happened on the way to humans was the lateral gene transfer of the entire genome of one species of single-celled organism to another, doubling the genome size at a single stroke. When calculating how long our genome took to evolve, what can we say about such an event except that it did happen or it didn't? So there's more room for some more error.


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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 38 of 60 (668169)
07-17-2012 8:59 PM
Reply to: Message 33 by Dr Adequate
07-17-2012 8:41 PM


Re: Not so fast
I did learn a lot here and appreciate the comments you made.
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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


(1)
Message 39 of 60 (668173)
07-17-2012 9:04 PM
Reply to: Message 37 by Dr Adequate
07-17-2012 8:57 PM


answers only generate more questions to ask - the lateral transfer of an entire genome - that sounds like something to study all by itself!
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bcoop
Junior Member (Idle past 1615 days)
Posts: 27
From: Maine
Joined: 07-14-2012


Message 40 of 60 (668174)
07-17-2012 9:06 PM
Reply to: Message 28 by Coyote
07-17-2012 1:47 PM


Re: Mathematical modeling
Sounds good - I will listen to it this weekend - thanks for the reference!
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Dr Adequate
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Posts: 15476
Joined: 07-20-2006
Member Rating: 4.0


Message 41 of 60 (668176)
07-17-2012 9:25 PM
Reply to: Message 39 by bcoop
07-17-2012 9:04 PM


answers only generate more questions to ask - the lateral transfer of an entire genome - that sounds like something to study all by itself!

I know that that can happen within species, I don't know if it's ever happened between species (I mean the transfer of an entire genome, partial transfers are common). But I don't see why it shouldn't.

Edited by Dr Adequate, : No reason given.


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caffeine
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Posts: 1214
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 3.5


Message 42 of 60 (668181)
07-18-2012 3:32 AM
Reply to: Message 32 by bcoop
07-17-2012 8:34 PM


Re: Generation lengths bogus
I need to print this out and study it - there is a lot on there - I wonder if we are in the midst of another mass extinction?

I think this picture is badly put together. It is labelled as if the centre is the past, and left and right are the present, but that's not actually how it's drawn, since molluscs (snails, claims and octopuses) lie right in the middle at the four billion year ago mark. It's more accurate to think of the whole outer rim of the diagram as the present. This gives the impression that there is far more diversity around today than ever before, but that's just because, as the caveat on the bottom says, they've missed out most extinct organisms.

As for whether we're undergoing another mass extinction, that's a matter of debate, but some would say yes. Here's wikipedia's article on it.


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Wounded King
Member (Idle past 1446 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 43 of 60 (668185)
07-18-2012 4:05 AM
Reply to: Message 42 by caffeine
07-18-2012 3:32 AM


Is it a bad figure?
I think this picture is badly put together. It is labelled as if the centre is the past, and left and right are the present

I think this criticism is somewhat unfair, there are nested arcs of dashed lines centered around the past and these lines intersect with the times on either side delineating specific regions corresponding to a time period, both the lines and the timescales have complementary colour coding for particular stretches of time. Certain of the lines are also labelled with specific events associated with a particular time period.

It's more accurate to think of the whole outer rim of the diagram as the present.

That is in fact exactly what the diagram shows.

There are plenty of elements which obviate your initial objection if you give the diagram more than a cursory glance.

TTFN,

WK


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Minnemooseus
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From: Duluth, Minnesota, U.S. (West end of Lake Superior)
Joined: 11-11-2001
Member Rating: 4.0


Message 44 of 60 (668186)
07-18-2012 4:08 AM
Reply to: Message 42 by caffeine
07-18-2012 3:32 AM


About the age and life diversity diagram
I think this picture is badly put together. It is labelled as if the centre is the past, and left and right are the present, but that's not actually how it's drawn, since molluscs (snails, claims and octopuses) lie right in the middle at the four billion year ago mark.

Those light lines that arch across the diagram are lines of equal age. Decreasing age radiates outward in all the directions from the 4 billion years ago marking at the bottom center. Instead of displaying the diversity of life on a straight line, they are displaying it on a clockwise outward spiral (or something like that).

The diagram is still pretty confusing.

Added by edit: I think the origin age of a major group of specific life-forms is at the inner boundary of the colored area. That is why so much boundary of the colored area is at the Cambrian explosion time line.

Added by edit 3: Note where lines end within the shaded area. That is that particular branch of the bush going extinct. The extinction times include those where a specific critter is illustrated.

Moose

Edited by Minnemooseus, : See above.

Edited by Minnemooseus, : Modify previous ABE.

Edited by Minnemooseus, : See above. Also changed subtitle.

Edited by Minnemooseus, : Modify edit 3.


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caffeine
Member
Posts: 1214
From: Prague, Czech Republic
Joined: 10-22-2008
Member Rating: 3.5


Message 45 of 60 (668196)
07-18-2012 8:00 AM
Reply to: Message 43 by Wounded King
07-18-2012 4:05 AM


Re: Is it a bad figure?
I think this criticism is somewhat unfair, there are nested arcs of dashed lines centered around the past and these lines intersect with the times on either side delineating specific regions corresponding to a time period, both the lines and the timescales have complementary colour coding for particular stretches of time. Certain of the lines are also labelled with specific events associated with a particular time period.

Point taken. I didn't see the dashed lines until you pointed them out. Maybe it's my the colours and resolution on my monitor, but they're very difficult to make out.


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