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Author Topic:   What mutations are needed for a particular trait (e.g. wings) to arise?
Archer Opteryx
Member (Idle past 1919 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 16 of 111 (345115)
08-30-2006 5:15 PM
Reply to: Message 12 by skepticfaith
08-30-2006 4:10 PM


Re: feathers and flight
skepticfaith writes:

Ok - that was an interesting read, but it does not cover what I am saying.

You asked several questions. I only addressed one: your request for a catalog of the changes that would be needed.

It's a good place to start. It helps to have a sense of that before getting into the specifics of how mutations arise and are selected. The article does a good job of listing the structures that are implicated in a transition from dinosaurs to birds.

The transition from dinosaur to archaic bird was really not so vast. Archaeopteryx is, skeletally, just another coelurosaur. But it had feathers, and a true flight capability.

(In fact, two specimens of Archie--The Solnhofen Specimen and the Eichstätt Specimen--were at first misidentified as Compsognathus, a ground-running coelurosaur. That's how dinosaurian its skeleton is.)

Coelurosaurs were already set up for the change. I mentioned the hollow bones and the high metabolism. They were also carnivores. One of the anatomical features that tends to go with predation is good eyesight--especially stereoscopic vision. Obviously, this is also helpful to a creature that flies.

The similarities are so strong that cladistics experts today no longer consider birds a separate category from dinosaurs. They have adopted the terms 'non-avian dinosaurs' for those groups that went extinct and 'avian dinosaurs' for those creatures whose eggs you eat every morning. Modern birds are coelurosaurs.


Archer

All species are transitional.


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Gary
Inactive Member


Message 17 of 111 (345123)
08-30-2006 5:38 PM


Another flying animal
A number of flying or gliding animals have been mentioned in this thread - insects, birds, pterosaurs, flying squirrels, and so on. One that has not been mentioned is Sharovipteryx mirabilis, a reptile which had a membrane across its hind legs that allowed it to glide. This makes it the only known animal that used a flight system dominated by its hind legs.

http://www.livescience.com/animalworld/060718_delta_wing.html


  
skepticfaith
Member (Idle past 4043 days)
Posts: 71
From: NY, USA
Joined: 08-29-2006


Message 18 of 111 (345124)
08-30-2006 5:40 PM
Reply to: Message 15 by Gary
08-30-2006 4:43 PM


Infinite possibilities?
quote:
You're right that random mutation alone doesn't cut it. That's where natural selection comes in. Natural selection works upon the random mutations to produce strings of beneficial mutations.

I understand this but what I am driving at is that the successive series of mutations is not likely to produce anything useful (even many generations apart and with natural selection) if as you phrased it

quote:
out of a practically infinite number of possibilities, that things could have turned out.

This is what I have an issue with. If the number of possiblities are infinite as you say - (and I doubt that they are) then evolution isn't highly improbable - it is impossible! Despite the time frame involved, it still wont be enough time for creative pressures to select the right mutations..
However, if this entire process was designed to stack the deck in favor of useful beneficial mutations - we can get what we observe right now. Of course this would imply either a designer or an intelligent process that is driving evolution. From a logical stand point this would make sense - but it certainly is not random, at least not with infinite possiblities ..

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Chiroptera
Member
Posts: 6814
From: Oklahoma
Joined: 09-28-2003
Member Rating: 4.2


Message 19 of 111 (345128)
08-30-2006 5:51 PM
Reply to: Message 18 by skepticfaith
08-30-2006 5:40 PM


Re: Infinite possibilities?
quote:
I understand this but what I am driving at is that the successive series of mutations is not likely to produce anything useful

But it isn't just a successive series of mutations. In one generation, there will be many, many individuals with mutations; there will be lots and lots of mutations in that generation. Of these, a very few mutations will be advantageous and selected for, and the individuals in the succeeding generations will predominately have that (or those) mutations. But the next generation will have its mutations, many, many mutations. A few of these will be selected for.

After many, many, many generations, the population will be rather different from the population at the beginning. In what way the population will be different would be impossible to predict at the beginning; however, it is entirely plausible after several tens of millions of years, the final population will be significantly different that the initial population.


"The fact that a believer is happier than a skeptic is no more to the point than the fact that a drunken man is happier than a sober one." -- George Bernard Shaw

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PaulK
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Posts: 15578
Joined: 01-10-2003
Member Rating: 2.9


Message 20 of 111 (345130)
08-30-2006 5:56 PM
Reply to: Message 11 by skepticfaith
08-30-2006 3:53 PM


Re: Is it possible mathematically?
quote:

How is this a bad argument?

For the reasons I gave. Instead of producing any attempt to make a valid estimate you just guess - without taking into account things like the fact that there may be many mutatiosn that give adequate protection, and that there are millions of people who might acquire one or more of these mutations. The fact is that jsut saying that something seems very unlikely to you is a bad argument when you have absolutely no idea of how unliukely it really is.

quote:

Besides I am not saying that the chances of one beneficial mutation is impossible just an entire series of them to give rise to this trait.

And this has the same problems - and worse, if some other trait appeared instead you would make the same argument about that. So you really need to argue about the probability of ANY trait evolving.

quote:

Thus your analogy to the lottery is incorrect. The analogy is more like the same person winning the lottery 1000 or more times..

You don't provide any argument that would justify the "thus". Not surprisingly because you are completely wrong. There is nothing equivalent to the SAME person winning the lottery multiple times. All you are doing is picking out a pattern in hindsight - which would be quite easy to do with any random data. All that is required is that SOME traits evolve which involve multiple mutations - which will be interspersed among mutations contributing to other traits. Really you are making the same mistake again. What actually happened is "very unlikely" - but like lottery winners it is very likely that you will find SOME sequences that, in hindsight are "very unlikely" - just as it is unlikely that a particular person will win the lottery - but very likely that someone will win the lottery.

Edited by PaulK, : Text trunvated on postinge


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jar
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Posts: 31672
From: Texas!!
Joined: 04-20-2004
Member Rating: 2.6


Message 21 of 111 (345149)
08-30-2006 6:18 PM
Reply to: Message 18 by skepticfaith
08-30-2006 5:40 PM


Re: Infinite possibilities?
However, if this entire process was designed to stack the deck in favor of useful beneficial mutations - we can get what we observe right now.

It kinda is, not towards creating beneficial mutations but only keeping those. The failures die. That is the filter called Natural Selection.

Of course this would imply either a designer or an intelligent process that is driving evolution.

No, not at all. It points to something that only keeps the successes.


Aslan is not a Tame Lion

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Gary
Inactive Member


Message 22 of 111 (345151)
08-30-2006 6:21 PM
Reply to: Message 18 by skepticfaith
08-30-2006 5:40 PM


Re: Infinite possibilities?
If I have a hundred dice, and I roll them all, there are a large number of possibilities. 6^100, to be exact. But even though this number is very large, that doesn't mean that it is impossible to get any particular combination. If I roll all the dice, I have to get some combination, even if that combination is extrememly unlikely.

Another way to think about it is like this: If I paint a picture, there is a virtually infinite number of ways I could make my brush strokes, so there is a virtually infinite number of different paintings I could paint. But that doesn't mean it is impossible to paint a painting.

I don't see why mutation and natural selection are not likely to produce anything useful, in your opinion. I think we have to agree on a definition of "beneficial mutation". I would define it as one which increases an organism's biological fitness, which is the ability of that organism to reproduce effectively. There many kinds of beneficial mutations - they could protect against disease, or help an animal evade predators so it can live long enough to reproduce, or the mutation can increase the number of offspring, or even lower the number of offspring, if these offspring are then more likely to grow up and reproduce. It could also do something more subtle, like allow for a particular nutrient to be absorbed in a new way, so the mutant is less likely to die of a deficiency in this nutrient.

In the case of birds, mutations in genes which affect scale growth could have resulted in downy feathers, which kept dinosaurs warm. These may have only been present when the dinosaur was young. Other types of feather, such as contour feathers, may not have started out as particularly aerodynamic. They may have been much smaller in relation to the whole animal, and they may have covered only the forelimbs. These could be useful in mating displays, in much the same way birds of paradise have elaborate displays which mainly show off their feathers. They could have grown longer, as peacock tails have, into something that improved agility on the ground and even could have been used for gliding. From there, gliding developed into powered flight which we see in modern birds.

This is an outline based somewhat on my speculation, but experiments have indicated that feathers are modified scales, and a number of fossil species have been found with impressions of feathers. Some could fly, some could not. Caudipteryx had long feathers on its forelimbs and tail, but does not appear to have been able to fly. These feathers may have been used to attract mates or for some other purpose. There also seem to be some dead ends - for example, Microraptor gui appears to have had four wings. Its fore and hind limbs had long feathers. You can think of this as another way birds could have turned out, with four wings instead of two, but for some reason, this didn't work out.


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Archer Opteryx
Member (Idle past 1919 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 23 of 111 (345154)
08-30-2006 6:23 PM
Reply to: Message 9 by jar
08-30-2006 11:09 AM


Re: just a couple questions
jar writes:

Are there also not intermediate examples of flight such as fish that soar and snakes and squirrels and several non-flying insects?

Sure. I live in a part of the world where fish fly. It's very exciting to see.

Interesting you say the word 'intermediate.' It's true these animals have very limited flight capabilities in our time. Yet they serve as excellent illustrations of the fact that creatures don't require the 'magic' arrival of a highly evolved feature. All they need is a mutation that stretches something a bit--a fin, some skin--and for the change to give some advantage.

Flying fish can't touch modern birds when it comes to flight skills. But they really do fly for short distances and this in itself confers a real survival advantage. It can make all the difference in evading a barracuda.

I suspect the ability of ancient fish to move into ever shallower water, and then onto land, came about in a similar fashion. The ability to get around in shallow water, and eventually on land, would be very useful in staying out of range of predators.

Doesn't the fossil record also show many, many failures, critters that had feathers but never developed the next step or critters that developed true flight but still died out or critters that were kinda in the direction of modern birds but also died out, were a deadend?

Right now a lot of new discoveries are being made. It's hard to say who is related to who yet, but it's clear a variety of feathered coelurosaurs were running around. Some lines evolved flight capabilities, some didn't, some who did later dropped the flight adaptation, and so on. Some lines represent bird ancestry and some represent, in the long run, dead ends.

You'll notice most of the newest dinosaur-bird fossils coming from China, where some unusually find sand in Jurassic times enabled the preservation in fossils of delicate structures that usually get lost, such as feathers, fur, and skin.

A very exciting find, Dromaeosaurus, is an example of a Velociraptor cousin with feathers. It didn't fly. But the 'raptors' were a succesful group of animals.
http://news.bbc.co.uk/2/hi/science/nature/1296102.stm

Here's a look at the flight characteristics of one early bird, Microraptor:
http://www.livescience.com/animalworld/051014_flying_dino.html

Here's a colorful scroll-through gallery of feathered dinosaurs:
http://www.livescience.com/bestimg/index.php?url=Avian_Velociraptor_00.jpg&cat=avianancestors

The Velociraptor--a ground-based dinosaur--had a wrist that enabled it to make a fast, sweeping lateral movement with its forearms. This feature helped it grab prey. What's fascinating is that the same movement is used by modern birds when they make their flight stroke. When birds flap their wings, they 'grab air' using the same gesture their ancestors used to grab prey.

The term 'failures', though, is a bit loaded. It implies that every line of coelurosaurs had to evolve into birds, so the 'successes' are those who make it and the 'failures' are those who don't. That's not really how it goes. The creatures just mated as they mated, mutated as they mutated, and went in their different directions. One result was birds.

Edited by Archer Opterix, : Concision.

Edited by Archer Opterix, : Typo.


Archer

All species are transitional.


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skepticfaith
Member (Idle past 4043 days)
Posts: 71
From: NY, USA
Joined: 08-29-2006


Message 24 of 111 (345171)
08-30-2006 6:53 PM


Finite possibilities - not infinite..
quote:
If I have a hundred dice, and I roll them all, there are a large number of possibilities. 6^100, to be exact. But even though this number is very large, that doesn't mean that it is impossible to get any particular combination. If I roll all the dice, I have to get some combination, even if that combination is extrememly unlikely.

But I know that onedye has 6 sides here..I thought that someone had already come up with a number with regard to mutations. Also what I am driving at is similar to this Intended mutationsthread.

. The entire process has to be preprogrammed - every example given so far, lottery, dice, etc is designed..

To say simply that it is random and not get into any specifics as to how is simply not scientific. Anyone can caluclate the odds of winning a lottery - why can't the same be done for a beneficial mutation on a specific creature. This is the mystery of Life though -- but to just dismiss the whole thing as random is ridiculous.. It was either designed directly or via a process similar to a computer program (even if there was some chance involved).


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Hawks
Member (Idle past 4468 days)
Posts: 41
Joined: 08-20-2006


Message 25 of 111 (345225)
08-30-2006 8:07 PM
Reply to: Message 12 by skepticfaith
08-30-2006 4:10 PM


Re: feathers and flight
Its like I can propose that it is more advantageous for a creature to have a longer tail and viola a mutation appears that gives this longer tail .. natural Selection ends up with more long tailed creature.. Now the creature needs to whip this tail for some reason (it would be advantageous in nature for some reason) and magically another mutation gives it a stronger more flexible tail ...Is this the way evolution works? Anything can just happen magically?

What you seem to be suggesting is that natural selection would have some kind of foresight as to what might become advantageous. It doesn't. Rather, certain individuals carrying certain mutations are more likely to leave more offspring, leading to those mutations becoming more common in a population. There is nothing magic about mutations. Natural selection merely makes individuals with a certain mutation be more reproductively succesful, while individuals with other mutations are less reproductively successful.


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dwise1
Member
Posts: 3847
Joined: 05-02-2006
Member Rating: 3.1


Message 26 of 111 (345230)
08-30-2006 8:25 PM
Reply to: Message 14 by skepticfaith
08-30-2006 4:38 PM


Re: Is it possible mathematically?
quote:
quote:
A more accurate model would be a few individuals within the population winning the lottery, which their offspring then inherit as would then their offspring (also being the offspring of others who "married into the fortune" rather than having acquired it themselves).

Of course of of these offspring would have to win the next lottery to aquire the next trait and so on and on.

I assume in that typo that you meant to say "Of course all of these offspring ... " -- that is the only possible actual meaning that I can think of; please correct me if I am mistaken.

As such, your statement is still wrong. Once one lottery is won, all (or at least most, depending on how we model inheritance) of the winner's descendents will have that trait and, as Gary pointed out, if it is selected for then it will spread throughout the population. As other winners appear, their descendents will also inherit and that trait will also spread and so on until many, if not most, members of the population possess most all of these traits. There is no need for every single sequential offspring to also win a lottery; if you believe that evolutionary theory says that that must be the case, then please support that claim.

quote:
For mutations to produce traits that are beneficial - the genetic code would have to be designed this way too.

How do you arrive at that idea? Remembering back to John Maynard Smith's textbook, "Evolutionary Genetics" (which deals directly with the subject of the mathematics of population genetics), the only kind of mutation that is of interest in evolution is genetic mutation (not developmental mutations, which are not heritable) and that there are basically four kinds of genetic mutation (I would need to go look that up again; it will be a few days before I'd have time). At the genetic level, there's nothing to judge a mutation as being either beneficial or detrimental; it is only through the expression of that changed genetic code that such a judgement can be made. BTW, many mutations (eg, base substitutions) are neutral, as evidenced by there being so many different versions of the same proteins. Ditto with gene duplication.

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Hawks
Member (Idle past 4468 days)
Posts: 41
Joined: 08-20-2006


Message 27 of 111 (345231)
08-30-2006 8:26 PM
Reply to: Message 1 by skepticfaith
08-29-2006 5:45 PM


Re: Is it possible mathematically?
Think about it like this - what are the all the possible errors due to mutation that could happen? And what is the likelihood that one of them will be beneficial? Has this been ever calculated mathematically?

There are certainly a good deal of "errors" that could happen. Some small (ie one base affected) and some large (thousands of bases inserted, deleted and altered, all in one go). In order to calculate the likelyhood of one being beneficial one would probably first have to determine empirically the fraction of mutations that are positive and those that are negative. I've only seen something similar to this being done for simple point-mutations, which does not reflect what really happens in real life. As far as I'm aware, a realistic model for this has not been done so far. But hey, there are thousands of articles published daily(?), so who knows? If you find one that does go into detail about this, I'd certainly be keen to know.

That's a bit of a non-answer, I suppose. So the absense of any kind of research into that area would mean that any kind of discussion concerning it would be speculative.


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dwise1
Member
Posts: 3847
Joined: 05-02-2006
Member Rating: 3.1


Message 28 of 111 (345232)
08-30-2006 8:29 PM
Reply to: Message 15 by Gary
08-30-2006 4:43 PM


Re: feathers and flight
quote:
We get a distorted view of the probabilities of these events because the fossil record is limited by various factors, like the rarity of fossilization, while modern animals all look different because they are the tips of the branches on the evolutionary tree. We don't see too many of the dead ends deep in the evolutionary tree (though we've found a few, like pterosaurs) and we also fail to see that the way things are now is only one way, out of a practically infinite number of possibilities, that things could have turned out.

Another one is that the fossil record normally only shows us the morphology and not the genetic code, the genetic code being where the actual mutations take place.

Several years ago in either Science or Nature there was an article about "green fossils", magnolia leaves that had been encased in mud such that some of their proteins survived. The morphology of the leaves showed very little if any change, whereas the protein sequences did show change.


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dwise1
Member
Posts: 3847
Joined: 05-02-2006
Member Rating: 3.1


Message 29 of 111 (345237)
08-30-2006 8:39 PM
Reply to: Message 20 by PaulK
08-30-2006 5:56 PM


Re: Is it possible mathematically?
quote:
quote:
Thus your analogy to the lottery is incorrect. The analogy is more like the same person winning the lottery 1000 or more times..

You don't provide any argument that would justify the "thus". Not surprisingly because you are completely wrong. There is nothing equivalent to the SAME person winning the lottery multiple times. All you are doing is picking out a pattern in hindsight - which would be quite easy to do with any random data. All that is required is that SOME traits evolve which involve multiple mutations - which will be interspersed among mutations contributing to other traits. Really you are making the same mistake again. What actually happened is "very unlikely" - but like lottery winners it is very likely that you will find SOME sequences that, in hindsight are "very unlikely" - just as it is unlikely that a particular person will win the lottery - but very likely that someone will win the lottery.

Another way of looking at it when working with a population is not by finding the probability of something happening, but rather the probability of it not happening, whereupon we find the probability of it happening by subtracting that probability from one.

In a fair-sized population over multiple generation, the probability that nobody ever wins becomes becomes extremely small. That there won't be any one who inherits from multiple winners also becomes very small. Which would make the chances of the population having descendents of multiple winners very good.


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Woodsy
Member (Idle past 1695 days)
Posts: 301
From: Burlington, Canada
Joined: 08-30-2006


Message 30 of 111 (345244)
08-30-2006 9:02 PM
Reply to: Message 20 by PaulK
08-30-2006 5:56 PM


Re: Is it possible mathematically?
I hope you will forgive me for butting in. I'm new and still learning the customs here. I recently read a book called "Lightning Strikes" about probability. The author points out that if you run a coin-flipping tournament with (I think) 1024 contestants, you are guaranteed to wind up with a winner who won ten times in row. You just wouldn't be able to predict who it would be beforehand. Perhaps this is related to the difficulty here?

Edited by Woodsy, : spelling


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