Can somebody please help me here?
As I understand it, evolution is based on the following two principles:
1 During reproduction, small "copying errors" occur, call them mutations.
2 Natural selection then works on these copying errors, and beneficial ones are preferentially selected for continuation. The sum of many such beneficial mutations, over large amounts of time, effect the changes in the species and may form another specie.
If this is correct, then please explain the following to me. If this is NOT correct, then we don't have to go any further and please correct my mistake.
Assuming, however, that it is correct, then I have a real problem with the formation of some existing, internally consistent systems.
Take for example the simple system of chicken and egg.
If this evolved from something else, (whatever that may have been) can someone please explain to me how this system could have come about by small, incremental, beneficial mutations from any other system?
Can the intermediate stages, even over millions of years, be postulated from a non-egg laying reproductive system to an egg-laying reproductive system?
I read somewhere the reply given by Richard Dawkin to the chicken-and-egg question. His reply was that the chicken obviously came first, and there must have been a primordial chicken that lay the first egg. I assume that this was a tongue-in-cheek reply, since nobody could postulate that a non-egg laying animal could, in one generation, suddenly develop the complicated biological mechanisms to allow egg laying. But maybe he was serious, who knows? But I find this reply intensely dissatisfying.
This is an honest request. Can somebody please help me here?
In peace
Cal Just
Originally posted by CalJustThis is an interesting question and probably one of those ones that, like the development of the eye, has confused and concerned so many anti-evolutionists.
Can somebody please help me here?
As I understand it, evolution is based on the following two principles:
1 During reproduction, small "copying errors" occur, call them mutations.
2 Natural selection then works on these copying errors, and beneficial ones are preferentially selected for continuation. The sum of many such beneficial mutations, over ...[text shortened]... ying.
This is an honest request. Can somebody please help me here?
In peace
Cal Just
(I'm guessing Dawkins was being humourous.)
Here's a cut and paste from wikipedia that works pretty well:
[blockquote]If the egg is defined structurally as the hard shelled thing, and the chicken a feather covered animal, the answer is still simple. Evolutionary scientists believe the first hard shell egg was the amniotic egg laid around 300 million years ago, and was laid by the animal who was the link between amphibians and reptiles. One of the first dinosaurs that we know had feathers was the Archaeopteryx, and came much later. Modern birds would not arise until 150 million years ago, descending from theropod dinosaurs.
In this case, the first chicken must have been the mutated offspring of a proto-chicken that laid the egg containing the first true chicken.
The crux of the matter is how to biologically define 'a chicken'. What level of genetic similarity or structural similarity determine whether an organism is a chicken? One can only define what was the first chicken after the fact, thus any definition of the first chicken becomes arbitrary. The question 'which came first?' ignores the complicated reality of speciation.
According to the principles of speciation, neither the chicken nor the egg came first, because speciation does not occur in simple, obvious units. In fact, evolution is about a slow transition in an overall population. What qualifies as “chicken” (ignoring the many diverse modern types of chicken) involves a wide range of genetic traits (alleles) that are not encompassed in a single individual and continue to be modified from generation to generation.
The transition from non-chicken to chicken is a gray area in which several generations are involved, and therefore which includes many many chicken-and-egg events, with no one step representing the whole. Since the result of the process is an incomplete transition into various new characteristics rather than one single blueprint, a new species, "chicken", is only identified in hindsight when the species can be obviously identified as different from its ancestral stock.[/blockquote]
Originally posted by CalJustIt would be better to ask how non egg laying creatures evolved from egg laying ones. Birds probably evolved from dinosoar like creatures which layed eggs, which probably evolved from reptile or amphibian like creatures which layed eggs which evolved from fish which layed eggs which evolved from something else which layed eggs. Dont sexually reproducing bacteria lay eggs?
Take for example the simple system of chicken and egg.
If this evolved from something else, (whatever that may have been) can someone please explain to me how this system could have come about by small, incremental, beneficial mutations from any other system?
Can the intermediate stages, even over millions of years, be postulated from a non-egg laying reproductive system to an egg-laying reproductive system?
And yes, not only can intermediate stages be postulated but they exist today for all to see both in the form of living animals and fossils.
The transition from egg laying to live birth is not uncommon in the animal world. The bird is an example of internal fertilization, which could be thought of as a step on the way to live birth, though that is not the only possible outcome.
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Originally posted by CalJustThe evolution is too complex but I'll try to give a very bried, simplified. synopsis.
Can somebody please help me here?
As I understand it, evolution is based on the following two principles:
1 During reproduction, small "copying errors" occur, call them mutations.
2 Natural selection then works on these copying errors, and beneficial ones are preferentially selected for continuation. The sum of many such beneficial mutations, over ...[text shortened]... ying.
This is an honest request. Can somebody please help me here?
In peace
Cal Just
1. Embyo.
2. Mutant protein develops "shell" around the embryo".
3. Lots of more "mutations" and we have an egg.
Basically, proteins are naturall selected to protect the developing feotus and eventually this culimnates in the egg.
But its probably better to read the posts above me.
Also, Dawkins was not referring to the development of the egg, but of speciation. Of course, the proto- chicken would have layed an egg- but its still not a chicken.
If it is the shell that is in question then it was the evolution transition to land animals that necessitated a shell capable of retaining water. I believe that most amphibians still require water to procreate, and it is obvious that in drier climates those with eggs better able to withstand dry conditions have an evolutionary advantage and a shell would be selected for.
Whether eggs or shells are under discussion, they both evolved way before the bird and there are many many examples of many different strategies throughout the animal kingdom. Infact, even plants lay eggs (seeds).
Originally posted by amannionIn this case, the first chicken must have
This is an interesting question and probably one of those ones that, like the development of the eye, has confused and concerned so many anti-evolutionists.
(I'm guessing Dawkins was being humourous.)
Here's a cut and paste from wikipedia that works pretty well:
[blockquote]If the egg is defined structurally as the hard shelled thing, and the chic ...[text shortened]... cies can be obviously identified as different from its ancestral stock.[/blockquote]
On this point, we are quite (almost) certain.
In fact, evolution is about a slow transition in an overall population.
So slow, in fact, that the entire process stopped with the current 'population' we see about us presently. Evolution (a process, remember, not a force of nature) knows when to stop the transition in order to 'achieve' the overall 'best' results. Natural selection is spectacular that way: 'working' so hard for billions of years, to stop--- frozen in time, as it were--- right where we are now, for our benefit.
Take the chicken, for example. Evolution has 'seen fit' to 'make' this wonderful bird completely defenseless, because evolution just 'knew' that it would also 'select' man to domesticate the bird and become its defense system. Ah, the searchless wisdom of evolution!
Originally posted by FreakyKBHFreaky you are truly an idiot. Congratulations, you have my vote for the Idiot of the World.
[b]In this case, the first chicken must have
On this point, we are quite (almost) certain.
In fact, evolution is about a slow transition in an overall population.
So slow, in fact, that the entire process stopped with the current 'population' we see about us presently. Evolution (a process, remember, not a force of nature) knows when to st ...[text shortened]... the bird and become its defense system. Ah, the searchless wisdom of evolution![/b]
Moving right past your obsession with evolution as a force of nature (wherever did you get that one?), why do you think evolution has stopped?
The modern chicken may well be defenceless - although I challenge you to take a peck from one - but that's the result of thousands of years of domestication: artificial selection, which Darwin recognised as an analogue of the natural process. The original wild chicken may well have been significantly more agressive and dangerous, but why would human breeders want to maintain that. Easier to select the stupid and calm ones and stick with them. (Actually come to think of it, maybe religion works like that - selecting for stupidity.)
Originally posted by twhiteheadEggs are fertilised in the bird before being calcified and pushed out of the body. I rather suspect that the transition from egg laying to vivipary is a simple variation in the egg laying habit, where over a period of evolutionary time. Perhaps successive generations retained their egg internally for longer. Initially this must have had some fitness cost, since not having the egg internally means the organism can run around faster etc, but having instead a live offspring would have the benefit or reduced vulnerability of the offspring / egg during development. Probably some cataclysmic event (esp the KT extinction) really tipped the balance.
It would be better to ask how non egg laying creatures evolved from egg laying ones. Birds probably evolved from dinosoar like creatures which layed eggs, which probably evolved from reptile or amphibian like creatures which layed eggs which evolved from fish which layed eggs which evolved from something else which layed eggs. Dont sexually reproducing ba ...[text shortened]... be thought of as a step on the way to live birth, though that is not the only possible outcome.
Originally posted by twhiteheadexcellent point.
If it is the shell that is in question then it was the evolution transition to land animals that necessitated a shell capable of retaining water. I believe that most amphibians still require water to procreate, and it is obvious that in drier climates those with eggs better able to withstand dry conditions have an evolutionary advantage and a shell would ...[text shortened]... f many different strategies throughout the animal kingdom. Infact, even plants lay eggs (seeds).
Originally posted by FreakyKBHEvolution hasn't stopped it's operation - what would make you think it had? As long as the environment is changing through time, natural selection will always have some material to work on. Of course, genome complexity will make evolution of new traits slower, but cataclysms release the breaks occassionally.
[b]In this case, the first chicken must have
On this point, we are quite (almost) certain.
In fact, evolution is about a slow transition in an overall population.
So slow, in fact, that the entire process stopped with the current 'population' we see about us presently. Evolution (a process, remember, not a force of nature) knows when to st ...[text shortened]... the bird and become its defense system. Ah, the searchless wisdom of evolution![/b]
Originally posted by CalJust"1 During reproduction, small "copying errors" occur, call them mutations."
Can somebody please help me here?
As I understand it, evolution is based on the following two principles:
1 During reproduction, small "copying errors" occur, call them mutations.
2 Natural selection then works on these copying errors, and beneficial ones are preferentially selected for continuation. The sum of many such beneficial mutations, over ...[text shortened]... ying.
This is an honest request. Can somebody please help me here?
In peace
Cal Just
This is one possibility, the other being normal, random gene combinations.
Suppose for example that human eye colour can only be blue or brown.
Having blue eyes in Humans gives a 100% chance of the offspring having blue eyes, whilst having brown gives a 50% chance of the offspring having brown eyes and 50% blue eyes. (brown eyes are the recessive gene here)
It can be seen that a brown eyed mother and blue eyed father (or vice-versa) have a 75% chance of a blue eyed baby and a 25% chance of a brown eyed one.
A brown eyed mother and brown eyed father have a 50% chance of a blue eyed baby and a 50% chance of a brown eyed one.
A blue eyed mother and blue eyed father have a 100% chance of a blue eyed baby and no chance of a brown eyed one.
By these odds, the population will be predominately blue eyed (about 80😵.
Now suppose that some cataclysmic event occurs such as a meteor hitting the earth which raises clouds of dust. This results in only brown eyed people being able to see. Blue eyed people are completely blinded and as a result are easy prey for the marauding, mutated, deadly dogs and cats.
After a while, most blue eyed people are dead whilst almost all the brown eyed people are alive.
Most breeding couples are brown eyed, meaning that there is a 50% chance of all offspring being brown eyed. Blue eyed babies tend to die quite quickly, as they can't see the vicious cockroaches which eat them alive.
The human population therefore goes from being predominantly blue eyed to being mainly brown eyed.
This is called natural selection, or the survival of the fittest.
Originally posted by howardgeeDogs and cats? What about the monkeys? What color eyes do walri have? Ark13, where are you?!
"1 During reproduction, small "copying errors" occur, call them mutations."
This is one possibility, the other being normal, random gene combinations.
Suppose for example that human eye colour can only be blue or brown.
Having blue eyes in Humans gives a 100% chance of the offspring having blue eyes, whilst having brown gives a 50% chance of the of ...[text shortened]... ing mainly brown eyed.
This is called natural selection, or the survival of the fittest.
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Originally posted by FreakyKBHI second ammanions vote that are the Idiot of the world.
[b]In this case, the first chicken must have
On this point, we are quite (almost) certain.
In fact, evolution is about a slow transition in an overall population.
So slow, in fact, that the entire process stopped with the current 'population' we see about us presently. Evolution (a process, remember, not a force of nature) knows when to st ...[text shortened]... the bird and become its defense system. Ah, the searchless wisdom of evolution![/b]
And what makes you think evolution has stopped?
And secondly, you are an idiot.
You clearly know nothing of evolution.
Lots of answers, none of which are in any way satisfying intellectually.
Ammanion
According to the principles of speciation, neither the chicken nor the egg came first, because speciation does not occur in simple, obvious units. In fact, evolution is about a slow transition in an overall population. What qualifies as “chicken” involves a wide range of genetic traits (alleles) that are not encompassed in a single individual and continue to be modified from generation to generation.
Waffle, waffle. Never mind the “wide range” etc, just explain a single solitary one to me, please! Whatever else changes, I would just like to know how this ONE characteristic came about!
The transition from non-chicken to chicken is a gray area in which several generations are involved, and therefore which includes many many chicken-and-egg events, with no one step representing the whole.
These are the ones I would like examples of please!
Since the result of the process is an incomplete transition into various new characteristics rather than one single blueprint, a new species, "chicken", is only identified in hindsight when the species can be obviously identified as different from its ancestral stock.
Actually, I never mentioned chicken, just any egg laying organism. I could just as well have used the, more complicated, “egg-worm-pupae-butterfly” system, which also, IMHO, cannot have come about by any incremental change from any postulated previous system
Twhitehead
And yes, not only can intermediate stages be postulated but they exist today for all to see both in the form of living animals and fossils.
The transition from egg laying to live birth is not uncommon in the animal world. The bird is an example of internal fertilization, which could be thought of as a step on the way to live birth, though that is not the only possible outcome.
More blather. Totally avoided the question. It is exactly the argument that: “They ARE here today, therefore they MUST have come about from something else!” that I find so utterly infuriating!
Conrau K
The evolution is too complex but I'll try to give a very bried, simplified. synopsis.
1. Embyo.
2. Mutant protein develops "shell" around the embryo".
3. Lots of more "mutations" and we have an egg.
Also, Dawkins was not referring to the development of the egg, but of speciation. Of course, the proto- chicken would have layed an egg- but its still not a chicken.
Yeah, sure. So what was the “egg-laying proto-chicken” before it laid its first egg? And what made that “pre-proto-non-egg-laying-chicken” suddenly develop that very complex egg-laying mechanism, which entails a complex set of interacting biological changes?
Sorry, dear evolutionists, you’ll have to do better than that. And I don’t think friend Dawkin was joking. He DOESN’T have a better answer! And neither do you.
In peace
CJ
Originally posted by CalJustCJ, it seems the only answer that would placate you would be "we don't know". Unfortunately for you, we do.
Lots of answers, none of which are in any way satisfying intellectually.
[b]Ammanion
[i]According to the principles of speciation, neither the chicken nor the egg came first, because speciation does not occur in simple, obvious units. In fact, evolution is about a slow transition in an overall population. What qualifies as “chicken” involves a wi awkin was joking. He DOESN’T have a better answer! And neither do you.
In peace
CJ[/b]
All higher animals have eggs, mammals included. The only differences between a bird egg and a mammal egg are size and calcification. Calcification could easily have progressively evolved as animal made their first transition from an aquatic habit to a terrestrial one. As twhitehead suggests it's a necessary adaptation for life on land, without vivipary (which is simply a retention of the egg inside the mother, and thus without the necessity for calcification). As ammanion also rightly points out, it was gradual, happenning over numerous generations. If you'd have put you or Kellyjay back then you'd have said "but they're only reptiles", and that'd be true. Because you're only seeing a snapshot of whats happening, perhaps in your entire lifetime you'd see 1 ten thousandth of one percent of the time required to make that full change from a soft amphibious egg to a hard-shelled reptile egg. You simply can't see something happening on this time scale. It's like trying to watch a tree growing in real time - pointless - but that doesn't mean trees don't grow!
Anyhoo, distractions aside, the egg in birds is simply that - an egg, just like a mammal egg, just much bigger. Big eggs allow for big offspring with necessarily longer gestation times. The first egg layers were probably quite small, but got bigger over time, in the same way that ancestral aurochs were smaller than modern cows.