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woolytoad
Skeptic Friend
313 Posts |
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Ricky
SFN Die Hard
USA
4907 Posts |
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Rubicon95
Skeptic Friend
USA
220 Posts |
 Posted - 02/02/2005 : 11:20:59 [Permalink]
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I saw this piece on Channel 2. It was really good but it left me with questions. The article says that
"Eventually, the evolved into a retina, the layer of cells and pigment at the back of the human eye".
How did it (light-sensitive spot) mutate into a retina as we see in animals? What forces could have cause it? Why was such a spot there in the first place? If these are favorable mutations but where are nature's rejects? (Eagerly await comments, crude rude funny, from the gallery :-) )
Take this link for example (The website is great!)
http://www.livescience.com/humanbiology/041117_running_humans.html
Was there a group of Sapiens who had a genetic quirk that caused this? A mutation in their anatomy to give them this advantage?
If you go by genetic dispersion, the answer is yes. These Sapiens had a favorable mutation that gave them an advantage over others.
Or did one start running on two legs and changed his genetic code in the process?
I don't buy into the second view. Some explained that the giraffes got there long neck due to each generation stretching to reach food. By that stretching they passed it down because their genes were changed. Or one day we will lose our pinkies due to lack of use. I hope that came across right. I think that is a very false view.
That is my issue with the way evolution is sometimes presented.
Aside from that based on the facts and observations at hand, it's a very sound theory.
Edit due to de-evolution of my grammar skills  |
| Edited by - Rubicon95 on 02/02/2005 11:22:34 |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 02/02/2005 : 11:36:04 [Permalink]
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The whole Evolution Boxed Set kicks butt.
By the way, Ricky, you might be shocked to hear that I'm a hunt-and-peck typer, but I've been doing so for some 26 years, so I actually use more than just two fingers. Really, now that I think about it, I don't hunt much anymore, either. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Cuneiformist
The Imperfectionist
USA
4955 Posts |
Posted - 02/02/2005 : 11:47:23 [Permalink]
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quote:
Originally posted by Rubicon95
I don't buy into the second view. Some explained that the giraffes got there long neck due to each generation stretching to reach food. By that stretching they passed it down because their genes were changed. Or one day we will lose our pinkies due to lack of use. I hope that came across right. I think that is a very false view.
My (limited) understanding is that you're totally right about this [b]Rubicon95[b]. Simply stretching your neck to get food says nothing about how long your children's necks are going to be. Similarly, my lack of using the pinky (indeed, since I never learned how to type properly-- the only time I use them is to link it to my index finger when I'm holding my putter, like this:
but that's about it...) doesn't mean my children (heaven forbid!) are going to have slightly smaller ones! (And what about the guy who doesn't have very much sex...?) |
| Edited by - Cuneiformist on 02/02/2005 11:48:02 |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 02/02/2005 : 12:19:59 [Permalink]
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quote:
Originally posted by Rubicon95
How did it (light-sensitive spot) mutate into a retina as we see in animals? What forces could have cause it?
Random mutation, natural selection, genetic drift, etc. But perhaps that's not the answer you're looking for.quote:
Why was such a spot there in the first place?
Random mutation, natural selection, genetic drift, etc. Surely you can see that sensing light might be advantageous in some situations? (Pun intended.)quote:
If these are favorable mutations but where are nature's rejects?
They either didn't survive, or they're still with us. There are, after all, a plethora of different kinds of eyes in the world, all the way from simple light-sensing organs (of the true jellyfish, for example), to the wonders of a hawk's visual acuity.quote:
(Eagerly await comments, crude rude funny, from the gallery :-) )
Dammit, do my comments have to be one of the three?quote:
I don't buy into the second view. Some explained that the giraffes got there long neck due to each generation stretching to reach food. By that stretching they passed it down because their genes were changed.
Lamarckian inheritance of acquired characteristics. Not all Lamarck's fault, but it got his name. This had pretty much been disproven prior to Darwin's Origin.quote:
Or one day we will lose our pinkies due to lack of use. I hope that came across right. I think that is a very false view.
We may. If creating pinkies saps enough resources from a person to make a significant reduction in reproductive success compared to non-pinkied people, that could induce a selection pressure to get rid of them. Things aren't that way now, but the future environment is largely unpredictable.
Of course, I need my pinkies. For the enter key, the shift keys, tab, etc.quote:
That is my issue with the way evolution is sometimes presented.
Yeah, a sloppy presentation of natural selection is now, and probably always will be, a problem. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 02/02/2005 : 14:46:13 [Permalink]
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Lamarck may have had the mechanism wrong, but he had one of the basic concepts, descent with modification, right.
His work was important enough to still be taught today, even if he just gets a footnote as a historical reference in the evolution sections of biology texts.
http://www.blackwellpublishing.com/ridley/a-z/Lamarckian_inheritance.asp
Also, I am a hunt-and-peck typer. I just use my thumbs (for the space bar) and the first two fingers of each hand. I could not learn to type in grade/high school. Despite trying, and failing, multiple classes. I don't really have to hunt on a qwerty board anymore either, and only have to look at the keyboard occasionally. I can do a good 40-50 wpm. On a good auto-correcting word processor, maybe 60.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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verlch
SFN Regular
781 Posts |
Posted - 02/03/2005 : 07:57:13 [Permalink]
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quote:
Originally posted by woolytoad
Apologies if this has been posted before. But its a nice little clip.
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
Boring! The eye is very complex but not as complex as would be expected if humans where so popular. With no evidence in the fossil record of macro evolution you have a hard time proving anything! |
What came first the chicken or the egg?
How do plants exist without bugs in the soil, and bugs in the soil without plants producing oxygen?
There are no atheists in foxholes
Underlying the evolutionary theory is not just the classic "stuff" of science — conclusions arrived at through prolonged observation and experimentation. Evolution is first an atheistic, materialistic world view. In other words, the primary reason for its acceptance has little to do with the evidence for or against it. Evolution is accepted because men are atheists by faith and thus interpret the evidence to cor-respond to their naturalistic philosophy.
For the time will come when they will not endure sound doctrine; but after their own lusts shall they heap to themselves teachers, having itching ears; And they shall turn away their ears from the truth, and shall be turned unto fables. II Timothy 4:3,4
II Thess. 2:11 And for this cause God shall
send them strong delusion, that they should believe a lie:
You can not see the 'wind', but you can see its effect!!!!
Evolution was caused by genetic mistakes at each stage?
Radical Evolution has 500 million years to find fossils of fictional drawings of (hard core)missing links, yet they find none.
We have not seen such moral darkness since the dark ages, coencides with
teaching evolution in schools. (Moral darkness)
For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places, EPH 6:12.
"Thus, many scientists embracing naturalism find themselves in the seeming dilemma recently articulated by biochemist Franklin Harold: "We should reject, as a matter of principle, the substitution of intelligent design for the dialogue of chance and necessity [i.e., Darwinian evolution]; but we must concede that there are presently no detailed Darwinian accounts of the evolution of any biochemical system, only a variety of wishful speculations."
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 02/03/2005 : 09:09:22 [Permalink]
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quote:
With no evidence in the fossil record of macro evolution you have a hard time proving anything!
Ok, now we can just call you a liar. Telling a lie is a SIN verlch. I wonder how many times you have told this particular lie...
You need to go and work up some new troll ideas. You're pretty much just a broken record these days, not even good for a laugh anymore.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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beskeptigal
SFN Die Hard
USA
3834 Posts |
Posted - 02/03/2005 : 14:25:38 [Permalink]
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Dave already said what I would have re all sorts of eyes do exist today. And the mechanisms by which we get from a light sensing cell to a complex eye are well understood, are not mysterious, are not full of gaps in the theory, and are testable thus hold up to scrutney.
So let me add a bit on the testing part. Now that DNA analysis is much easier, thanks to PCR lab procedure advances, the science is revealing details on the genetic processes at a tremendous pace. Here's something I wrote in the past on this subject. I haven't reviewed it too closely so if there are errors let me know.
How genes work
All living organisms have a DNA or RNA map that contains all the instructions for building that organism.There are billions of lines of digital code in DNA. There are 4 nucleosides in various combinations which make up the code. Humans have about 3 billion base pairs of the 4 nucleosides in their DNA map. When the DNA code changes occur, detrimental changes die out, neutral and successful ones go on reproducing. Changes accumulate over time. That is the simple version.
But what additional information is now known about the process?
Segregated function
One question the theory of evolution must answer is how do changes accumulate and still function? How do single mutations change fins to limbs to wings?
The answer is in how genes are structured. Genes are divided up. Where a scale goes (covering), how it forms (embryo), what it does (protects the inside), what structures are within (like oil glands), and what it looks like (camouflage or attract a mate or both) are just a few examples of things that are controlled by separate genes.
If you make a very small change, you can get a very big functional result. Take the mutation that causes a person to have 6 fingers or toes. The only change that has to occur is in the number of digits. All the rest of the structure of a finger is encoded in separate genes.
Separate genes have been found to work in more than one species. You can put a rabbit embryo gene that directs the growth of the eye into a fruit fly embryo which has had the equivilent gene removed. You get a normal compound fruit fly eye in the right place.
The same genes continue to function and remain the same even as the organism evolves into another species. We are using the yeast genome to find human genes. The yeast is a much simpler organism yet many of our genes are the same!
Fruit fly genes can be manipulated to get antenna where legs belong or legs where antenna belong. The gene that initiates a leg or an antenna is separate from the gene that determines what an antenna or leg are. As little as one change in one nucleoside on any DNA strand can impact a change in the organism.
What it boils down to is as the gene code is deciphered, the mechanisms to get limbs, whether wings or arms, is essentially the same from organism to organism. The basic structure is then modified by the specific additional genes. It's sort of like the underlying structure of a wall with different wallpaper.
Single mutation, huge impact, small impact or no impact
Another stumbling block in understanding evolution is understanding what single nucleoside changes in the code can do. The change may do nothing since there is a lot of redundancy built in to the code. The change may have a small, moderate, or large impact if it changes the code in a critical place. And, a change may have a large impact by turning a gene on or off completely.
Mutations are not always single nucleoside exchanges. Sometimes the gene may lose or gain a whole strand of DNA.
How mutations occur
There are several ways new information is created when DNA replicates.
1) steady rate of errors in copying:
Every time a cell divides an error can occur. In a developing fetus, a complete change can result. In a grown organism, you can get things like cancer developing.
2) recombining DNA during sexual reproduction:
Different combinations of DNA, even if no new material were to result, spread genetic changes into larger populations. In reality, genes from the mother and father are not always either or. Sometimes the combination differs from the two original genes because of interaction with eachother. Brown eyes plus blue eyes might result in hazel.
3) acquiring new DNA:
This occurs in other ways besides sexual reproduction. A virus is made of either DNA or RNA. When a cell is infected the DNA or RNA can become part of the infected cell's DNA or lead to the creation of new DNA in the infected cell. When you have a cold sore that recurs, you are not getting a new infection, the virus has moved into your cells permanently, and is now part of that cell's genetic code.
4) losing DNA:
Whole pieces of DNA might become inactive due to a simple nucleoside copy error. Whole pieces might break off.
5) bacteria and viruses have special mechanisms:
Bacteria exchange genetic material with unrelated species via 'plasmids', (little packets of genetic material). Some single celled organisms exchange genetic material as offspring are produced. Some organisms fuse their genetic material and some viruses exchange whole genes when 2 strains infect the same host. It amounts to gene shuffling.
Selection processes
Selection forces or pressures determine the path evolution takes. Mutations occur like clockwork. Some genetic molecules are more stable and some mutate more readily. The environment, diseases, mates preferences, and purely random occurances are the main selection processes which determine which genetic changes will proliferate.
Successful traits are not necessarily single function traits. Sometimes a beneficial trait will have a detrimental trait combined with it. The overall process should be viewed with the complexity it contains.
The more mutations, and, the more frequent & number of offspring, the more successful the organism is in adapting to changes in the organisms' biosphere. Variability has been shown to be more successful than too much specialization since a varied population is more likely to have survivor traits should the species be threatened.
Life evolves at different speeds. Major extinctions narrow the genetic line which starts again with a smaller number of individuals. Animals migrate and become isolated from other groups. Food sources come and go leading to lots of variation. During human evolution, genetic evidence shows the human population was once large but was reduced to as few as a thousand members then repopulated the planet.
Irreducible complexity argument
How can random genetic changes go from a scale to a feather if there is no function of the inbetween structure?
Irreducible complexity is not supported by the evidence. The eye doesn't seem to be irreducible, but when you look at examples in nature, it turns out the evolution of the eye really can be traced back to its very beginnings as a mere light sensitive cell. The problem here is conceptualizing the transitions, it isn't that the transitions do not exist.
Transitional traits are all around. All forms of circulatory systems exist today. Animals that live in and out of the water, in salt water and in fresh water, colonies of cells that act as an organism, colonies of cells that have symbiotic relationships with other species and act as a connected organism are some examples.
1st molecules to whole organisms
After the last big blast of asteroids that resurfaced the Earth, (~3.9 billion years ago), fossil evidence shows that life was well established only 50 million years later. After another 350 million years sophisticated microbes were alive. "Molecular fossils from Greenland tell us that some kind of life was on Earth ... by 3.85 bill |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 02/03/2005 : 17:38:32 [Permalink]
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Don't forget the impact, particularly in plant evolution, of sympatric speciation, especially polyploidal.
There are several examples of this within the last 100 years, some with significant morpholigical alteration from the parent species. Add the effects of this up over even a few hundered thousand years and it can account for some tremendous evolutionary alterations in the appearance and function of species.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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beskeptigal
SFN Die Hard
USA
3834 Posts |
Posted - 02/04/2005 : 01:35:34 [Permalink]
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I had to look up sympatric speciation. Unfortunately I got more than I bargained for.
• Allopatric speciation
• Peripatric speciation
• Parapatric speciation
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| Edited by - beskeptigal on 02/04/2005 01:37:03 |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 02/04/2005 : 09:44:17 [Permalink]
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quote:
I had to look up sympatric speciation. Unfortunately I got more than I bargained for
Doh! My bad. (was tired when I posted that) I should have explained more. Sympatric speciation is just used to describe speciation events among a parent population that share the same geography. Allopatric speciation is the opposite, being driven by geographic isolation of a portion of the parent population (a good example is Madagascar after it drifted away from the African coast, and of course the Galapagos).
Polyploidal changes occur when (mostly in plants) the number of chromosome copies changes from the usual diploid number AND the resulting organism remains fertile. Often these are not capable of interbreeding with their parent population, and are therefore a new species. This can occur even between members of two different plant species sometimes.
(edited to add this link to pliody speciation in plants)
http://evolution.berkeley.edu/evosite/evo101/VC1iSpeciationPlants.shtml
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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| Edited by - Dude on 02/04/2005 09:48:20 |
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tkster
Skeptic Friend
USA
193 Posts |
Posted - 02/05/2005 : 14:30:53 [Permalink]
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quote:
Originally posted by verlch
quote:
Originally posted by woolytoad
Apologies if this has been posted before. But its a nice little clip.
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html
Boring! The eye is very complex but not as complex as would be expected if humans where so popular. With no evidence in the fossil record of macro evolution you have a hard time proving anything!
It's ironic that you are making an assertion with NO evidence.
tk |
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beskeptigal
SFN Die Hard
USA
3834 Posts |
Posted - 02/05/2005 : 15:16:41 [Permalink]
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No evidence in the fossil record for eye evolution, Verlch? Well d'oh! Soft tissue body parts don't often fossilize.
Dude, I was teasing about the terminology. It was all Greek to me, but you aren't necessarily responsible to dumb stuff down for us. 
I often debate about should I try to meet a certain reading level. Especially on the BABB forums since a lot of kids read there. But in the end, I found it's too much work. Once in a while I might change something, but not on a regular basis. |
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 02/05/2005 : 15:45:24 [Permalink]
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quote:
It was all Greek to me, but you aren't necessarily responsible to dumb stuff down for us.
If communicating with people is the goal, then it's the responsibility of the writer to know the audience. So, unless the target audience are all biology majors, it would have worked better if I had explained more.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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