Author Topic: proof of evolution  (Read 7862 times)

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Offline WMCoolmon

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Do we really need another evolution debate at HLP?

:sigh:

Why didn't we have all this enthusiasm when we actually had a debate forum? :p
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Offline Janos

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Do we really need another evolution debate at HLP?

:sigh:

Why didn't we have all this enthusiasm when we actually had a debate forum? :p

Yes we do, and because the debate forum sucked
lol wtf

 

Offline WMCoolmon

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Yes we do, and because the debate forum sucked

Sorry to spill sunshine on your funeral.
-C

 

Offline Janos

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Yes we do, and because the debate forum sucked

Sorry to spill sunshine on your funeral.

no i'm just hungover ok
lol wtf

 
Some may not have had blood, but you're telling me that the development of the bloodclotting reaction came BEFORE creatures even had blood?  That's preposterous!
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Offline MP-Ryan

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Some may not have had blood, but you're telling me that the development of the bloodclotting reaction came BEFORE creatures even had blood?  That's preposterous!

You don't understand natural selection at all, do you?

And for the record: blood clotting reactions would have come before blood became an essential system in higher animals.

When blood became an essential system, animals that had the genes and proteins required for clotting would survive injuries that cause bleeding, while animals without those specific genes and proteins would have died out.  Their descendants evolved into the animal species we see today.  Those genes and proteins had and still have other functions besides clotting; clotting was merely a trait not under selection pressure which mutated in and out until it ended up under selection pressure.

This is why we see diseases where people (and animals) have either minimal or no clotting reaction - its a deleterious spontaneous mutation, which happens all the time, and is genetically analogous (or similar, but not identical to) circulatory animals which lacked the clotting reaction - and individuals today die out just the same way.  (Of course, it's a recessive trait, and also caused by spontaneous mutation, so it will never be weeded out of the population entirely).

Quit calling things perposterous or unbelievable just because YOU don't understand them.  The science is very well understood.  This is not merely theory, it is biological fact.  If that's inconvenient for religious nuts who can't be bothered to educate themselves for fear of disrupting their doctrinal beliefs, tough ****.

I'm tired of you and others trolling these threads and I'm tired of rehashing basic college-entry-level and high school biology because you people insist on being so damn think.  My patience is wearing very thin, and I daresay it's probably showing in my tone right now.

Educate yourself, or quit posting about it.

Someone please lock this; the original report, thread and discussion has nothing actually to do with the article on which it was written, and now we're moving well beyond it into the usual tripe that appears in evolution threads around here.
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Well, Ryan, FYI, I am entry-level college-educated, and am still in the process of educating myself, so forgive me if I don't know everything about everything just yet.

Now, to the topic:  Why would blood have been formed if it wasn't essential?  I thought natural selection was driven by necessity.  So how could we grow to need blood if at one time we were fine without it?
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Offline karajorma

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That isn't the topic. Quit trolling.

MP-Ryan, I wouldn't mind hearing an explanation of what these guys actually discovered.
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Offline Ghostavo

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I thought natural selection was driven by necessity.  So how could we grow to need blood if at one time we were fine without it?

If an individual of a species develops a trait that is advantageous, it's chances of survival will be better than those without it (hence why it is advantageous), and thus enable for that trait to propagate through the species' gene pool.

Simple isn't it? And to think I've never had a biology class above high school level as most people in this forum who seem to understand this. Makes me wonder what happens in science classes in other countries where people have doubts about evolution.
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Offline Mika

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Note that this topic is a hornet's nest. But on the other hand, gasoline and matches tend to make a short work of them - and I have a lot of gasoline!

I don't even claim to understand everything about biology or the fine details of evolution. But I can answer your question with some accuracy, I hope. Rest of the biology people can fulfil and correct the used terms, if they bother.

Current understanding is that the life evolved from single cell type creatures that don't have a system that could be called blood. Instead inside the cell there is a type of liquid that fulfils the whole volume of the cell, minus the cell organs (and at this point my English vocabulary seriously sucks). The necessary information is carried from organ to organ through this liquid.

There are several steps of evolution between the invertebrate and the single cell creatures, but I'll try to make this answer short so. When you look at spiders for example, they have a kind of blood, but it flushes all around the body pretty much like with the single cell creatures. But spiders do have a heart and lungs, if memory serves, so here is already a quite evident difference.

If there exists creatures like the spiders and generally the invertebrate(=no bones around the spine if the fancy word was incorrect), why did we evolve to have such complex blood circulation system? This is a little bit of guess work, but I would suppose that the larger animals have had competitive edge at multiple points of history, and the spider type of blood circulation does not work with mammals whose brain are located much higher than heart. If it were like that gravity would keep blood concentrated on the lower part of the body and the brain would not function. You can continue with this line of thought by yourself by filling the evident gaps in the explanation, I suppose.

Mika
Relaxed movement is always more effective than forced movement.

 
My point is, and I'm not trying to troll here, I'm honestly curious to see how tihs works out from your perspective, is how a system which requires A, B, C, D, E, F and G to be in place simultaneously, and not a single one of those can be lacking, can come to be, especially when A by itself needs its own group of things to be in place for A to function.  I just don't see how it's possible for all the things we require to live to  have come to be all at once.  My example was blood clotting.  In order to have blood, we need a pump (the heart), a way to infuse it with the things we need (lungs and hemoglobin), a way to keep from losing all of it (blood clots), and a system to transport it in (blood vessels).  I get that this all wasn't necessary before organisms grew beyond being two cells thick, and seawater acted as "blood."  But in order to be three or more cells thick, it needed capalaries.  How then do we get this jump to the entire circulatory system?
Could we with ink the ocean fill, and were the skies of parchment made
Were every stalk on earth a quill, and every man a scribe by trade
To write the love of God above, would drain the ocean dry
Nor could the scroll contain the whole, though stretched from sky to sky!

 

Offline Mika

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Also, please note that the larger the volume of the animal, the harder it gets to get the fresh blood to circulate around every region. So the driving factor is not only gravity, but more correctly the speed of which you can get fresh blood to organs and the amount of blood needed to carry necessary amount of oxygen and nutrition to all regions. With large mammals the blood would not move quickly enough to sustain life of those areas with a invertebrate type of circulation. Also, the large mammal would need a massive amount of blood to sustain itself.

So, the standing position of human is quite recent evolutionary step, and I'm wondering how well does the human withstand the blood pressure gradients and what will be the next evolutionary step if you think human's blood circulation. Pushing blood more effectively from the lower limbs to heart perhaps?

Mika
Relaxed movement is always more effective than forced movement.

 

Offline karajorma

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Given that somewhere between 1 in 3 and 1 in 5 people die of heart problems (depending on who makes up the stats) it does seem likely. Although that said we tend to die after having children so the selection pressure isn't as high as you'd expect from that statistic.
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Offline Kosh

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Well, Ryan, FYI, I am entry-level college-educated, and am still in the process of educating myself, so forgive me if I don't know everything about everything just yet.

Now, to the topic:  Why would blood have been formed if it wasn't essential?  I thought natural selection was driven by necessity.  So how could we grow to need blood if at one time we were fine without it?

Because it isn't essential to all animals. For example: Ants

(from http://www.thesahara.net/ants.htm)

Quote
For example ants do not have any lungs. Oxygen is absorbed through minuscule holes that are all over the body; Carbon Dioxide leaves through the same holes, but ants do not breathe. They have no blood vessels and the  heart is a long tube that circulates a plasma-like liquid from the head to metasoma.

Have you ever wondered why an ant doesn't bleed when it loses a limb or any other body parts?
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Offline MP-Ryan

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MP-Ryan, I wouldn't mind hearing an explanation of what these guys actually discovered.

OK, a little background:  the entire developmental lineage of C. elegans (one of the nematodes under study) is mapped.  There are an exact number of cells in every adult, and we know exactly where they came from.  You can trace the worm from single-cell to adult through its cell divisions, which is an extremely useful tool for studying developmental genetics, and subsequently developmental evolution.

More background:  Believe it or not, not all species develop the same organs in the same ways.  There's a rather famous example that plagues developmental biology students everywhere.  Humans, chickens, zebrafish represent three very different vertebrates.  During the first hours of embryonic development, they all look the same but their gene expression patterns are wildly different.  In early development, they all look wildly different but their gene expression patterns are virtually identical.  Mid-way through development they all look very much the same, but their gene expression is totally different again; and finally, in adulthood they not only look different but their gene expression patterns are totally different.  Why?  Because there are conserved genetic and physical stages of development, necessary steps which MUST occur to produce a healthy organism.  Gene expression always preceeds the physical result, which is why we see the pattern we see.  But the point is that we can produce the same systems in different ways, as long as certain essential points are reached.

This study goes a step beyond that - they are looking at the evolution of developmental systems in these worms.  And what they've found is that the observed differences in how the worms produce their vulva (the vulva is essentially the same in adulthood for all of the species) are not random; random mutations do not account for the variance in vulval system development, but rather the system tended to evolve directionally in certain ways, partially depending on the presence or absence of selection pressure.  The hypothesis they've partially discredited believed random mutations accounted for the variation in development of the vulva - that is, the development of the system would vary quite widely with the end result being the same.  This paper says no - the system as a whole tends to evolve along very specific lines, which can revert and converge.  Thus, developmental systems are evolving in a directional manner rather than a purely random one.

It forces a re-thinking of the problem I mentioned earlier in vertebrates, because the conventional wisdom is that only certain stages of each developmental pathway are required, whereas this is suggesting that, on a system level at least, the pathways themselves evolve as a whole and that individual elements are not simply subject to isolated changes.  The whole pathway is pushed in a certain direction, even though the end result of it remains the same.  Essentially, their phylogenetic analysis showed that certain pathway patterns tend to show up which can be traced in an evolutionary lineage through selection, rather than merely the result of random changes to the development of the vulva in each species.

Bottomline:  If we see a different developmental system producing the same vulval structure in different worms, it's due to selection pressures acting on each developmental system which bias the direction of change, and not simply the accumulation of a series of random mutations within the system that have no impact on the end result.

I hope that explains it.  I've been re-reading the article and I'm still trying to wrap my head around it myself, so I imagine my explanation here isn't all that clear.  Kudos to you if you can decipher it.

For anyone with journal article access, here is the reference information:

Quote
Current Biology 17, pp1925–1937, November 20, 2007
Trends, Stasis, and Drift in the Evolution of Nematode Vulva Development

Karin Kiontke,1,* Antoine Barrie` re,2 Irina Kolotuev,3
Benjamin Podbilewicz,3 Ralf Sommer,4
David H.A. Fitch,1 and Marie-Anne Fe´ lix2

...and honestly, all you have to do is look at the title to see that the Slashdot article author was apparently on crack.
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Offline Dark RevenantX

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My God.  Every time "evolution" is in a thread title, this happens.  Every.  Time.

 

Offline jdjtcagle

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 :lol:

How fun to watch the anger in peoples eyes over this...  :D

It isn't that hard to have a civilized discussion... errr... maybe?
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Offline Bobboau

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ok, well lets look at it this way. lets say you want to make a "PECAN PIE" well you need 'P', 'E', 'C', 'A', 'N',  'P', 'I', and 'E'. ok now lets just assume that you have made one somehow, and thus you have the constituent letters, but now you find that you are lacking in some vital plumbing supplies, you need a "CLEAN PIPE" something totally unrelated to pecan pie, well if you look all you need to do is find an 'L' somewhere and you can take the parts you were useing for the pecan pie and make the clean pipe!
:)

just because removing one part causes a complex system to stop working as it currently does, it does not mean that it is totally useless without that one part.
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Offline karajorma

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The move to comments about blood clotting occurred after the original irreducible complexity argument about bacteria flagellum was conclusively proved to be complete and utter bollocks. The original argument was that flagellum required 54 separate parts in order to work and was therefore to complex to have evolved. Someone then pointed out that there were creatures alive right now which only had 8 of the supposedly irreducibly complex parts in it and the whole thing fell apart.

So now we get comments about blood clotting instead because although it's the exact same faulty thinking as it was with flagellum no one has found such a conclusive way of proving what utter bollocks the whole thing is and the people who seem to think it's a problem for evolution and therefore proof of  irreducible complexity probably couldn't understand the explanation for why it's not a problem.

But make no mistake. This is the same argument again. And it's just as wrong. It's just not as obvious.

Bottomline:  If we see a different developmental system producing the same vulval structure in different worms, it's due to selection pressures acting on each developmental system which bias the direction of change, and not simply the accumulation of a series of random mutations within the system that have no impact on the end result.

Thanks. That's mostly a little above my head but I was at least able to get the gist. And you're right. They need better science writers as what that paper was actually about is nothing like what they said was going on.
« Last Edit: January 20, 2008, 09:55:52 am by karajorma »
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