How can scientists possibly know ... ?? An open exploration thread

[holdon]

Quotation marks are unnecessary. Scientific journals are scientific journals, not pseudo-"scientific journals". Ditto with scientists.

So sorry you're offended. But what is science?

1. They are not "exactly alike". Sure they are recognizable as being of the same family as the fossil forms, but they are different species and often a different genus.

How do you know? How do you know the worms that have not evolved for millions of years were a different species? Or is this due to the spandex of species taking whatever contours you want it to take?

2. Mutations alone do not force evolution. Natural selection does. And natural selection can prevent change as well as cause change. When a species is well adapted to its environment, most changes will make it less well adapted. Natural selection always favours the better adaptation, even if it is the status quo.

So, if say worms are well adapted in all environments they have lived in so far, there would be no reason for worms (or any other "primitive" organisms that are still around today) to evolve into something else. Which means that there was never a reason for them to evolve in the first place.

3. As a source of selective pressures, how much has the deep ocean changed in the last 500 or so million years?

Why the deep ocean?? Why not take my backyard?

If the first population is the source population and does not have these alleles, what cause, other than mutation, exists for the subsequent population to have acquired them?

If the entire source population did not have the base sequence or codons, then we would have to assume these were mutations. But we mostly don't know "what the source population" was of any of these things, even less what their genome looked like.

 

[Mallon]

I am at heart didactic. A real teacher must either have infinite hope or give up immediately.

Can't teach if the students aren't listening.

 

[holdon]

If 60 mutations in every zygote is not "lots" and "all the time" what is?

Well, that is certainly a lot. And considering that possibly upwards of 99% of these are detrimental (or take any number you like), you wonder that the species still exists....and didn't self-destruct. Or do we have now external selection pressures adjusting at the same rate?

 

[Mallon]

Case in point, shernren:

But New genetic material is detrimental in 99% of the cases..... and will get eliminated.

Incorrect. Most mutations are neither beneficial nor detrimental. Of the small minority that are not neutral, most are detrimental.

Well, that is certainly a lot. And considering that possibly upwards of 99% of these are detrimental (or take any number you like), you wonder that the species still exists....and didn't self-destruct.

QED.

 

[gluadys]

Well, that is certainly a lot. And considering that possibly upwards of 99% of these are detrimental (or take any number you like), you wonder that the species still exists....and didn't self-destruct. Or do we have now external selection pressures adjusting at the same rate?

Luckily for you most mutations are not detrimental. Most have no discernible effect on fitness one way or the other.

 

[JesusChrist24]

DICK To Jesus' ugly stupidity that is christianity. The so called "Pope" is a pedophile that rapes children and talks about beleiving in jesus what the [wash my mouth][wash my mouth][wash my mouth][wash my mouth] is that [wash my mouth][wash my mouth][wash my mouth][wash my mouth]. You are all stupid idiots to beleive in that Jesus is the moron messiah, for he will never come. Jesus has abandoned this [wash my mouth][wash my mouth][wash my mouth][wash my mouth] planet long ago, and we won't return. Don't start with the bible [wash my mouth][wash my mouth][wash my mouth][wash my mouth] when you read this! It's a book for idiotic morons just like you. The bible itself is an old Documentary book that some high guy wrote. This religion, along with all the other ones is the most idiotic ever. If we didn't have religion in the middle ages then we would live in the [wash my mouth][wash my mouth][wash my mouth][wash my mouth]ing future. You stupid idiots destroyed it all! Jerks. DON'T BAN ME FOR SPEAKING THE TRUTH!

 

[USincognito]

How do you know the worms that have not evolved for millions of years were a different species? Or is this due to the spandex of species taking whatever contours you want it to take?

Contrary to popular myth isn't created with toothpicks, marshmellows and imagination. The genetic evidence behind cladograms for extant species is pretty solid. In terms specifically of the ceolocanth which gluadys mentioned, you might check out these webpages.
http://www.dinofish.com/biologyandbehavior.html

 

[holdon]

Luckily for you most mutations are not detrimental. Most have no discernible effect on fitness one way or the other.

But we have only beneficial ones in sufficient quantities to ensure a "progression" of the species into a new species, (only if and when natural environment permits their retention)whereas comparitively to those we have a thousand times more detrimental ones that result in downright destruction of the species, more or less regardless of natural environments.

By the way, what you those that you say have no effect on the "fitness", might well have an effect sooner or later.

 

[gluadys]

But we have only beneficial ones in sufficient quantities to ensure a "progression" of the species into a new species, (only if and when natural environment permits their retention)whereas comparitively to those we have a thousand times more detrimental ones that result in downright destruction of the species, more or less regardless of natural environments.

http://cas.bellarmine.edu/tietjen/Laboratories/evolgame.pdf
http://foru.ms/showpost.php?p=14449626&postcount=5

Is the problem that you have not read these links yet, or that you have read them but don't understand them?

It doesn't matter if we have a thousand more detrimental mutations than beneficial mutations. Natural selection will act to purify the species of detrimental mutations and distribute beneficial mutations widely.

Let's look at the pepper moth simulation. It begins with supposing that in our sample of moths, the allele for melanism and the allele for absence of melanism are equally distributed. i.e. 50% or 0.5 of the alleles will produce melanism an 0.5 will not. In a standard Hardy-Weinberg distribution this will give you p^2+2pq+q^2 or (0.5*0.5)+2(0.5*0.5)+(0.5*0.5)=0.25MM, 0.5Mm, 0.25mm

M=allele for melanism MM homozygous condition
m=absence of melanism mm=homzygous condition
Mm=heterozygous condition. Since the allele for melanism is dominant, this genotype produces melanism

So 3 out of 4 or 0.75 of the population exhibits melanism.

In the absence of selective pressures, we can predict that these frequencies will be pretty much the same in the next generation.

But look what happens when you get a selection pressure.

This exercise assumes a doubling of the population from one generation to the next. Beginning with 150 moths, they would expect 300 in the next generation. But they simulated some loss due to predation. So they got 240 surviving moths. Had the predation not been selective, we would still get the same proportion of alleles in the 0.25MM+0.5Mm+0.25mm distribution or 60MM+120Mm+60mm individuals among the 240 survivors.

Instead we find 80MM+130Mm+30mm. From this we can calculate the ratio of each genotype as 0.33MM+0.54Mm+0.13mm.

Clearly the frequency p of the M allele has increased at the expense of frequency q of the m allele.

Instead of a 50:50 distribution you now have a 60:40 distribution.

If the selection pressure is maintained, the proportion of M alleles will continue to rise and that of m alleles will continue to fall. If the selection pressure is reversed to favour the m allele you will see the ratios reversing as well.

This is the sort of math I used to show the changing ratios in various scenarios--including one in which the beneficial mutation had to balance off two detrimental mutations. (See second link above.)

I can explain the results in more detail if you wish, but the results clearly show that even when coping with multiple factors, detrimental traits will tend to decrease in frequency while beneficial traits will tend to increase in frequency.

By the way, what you those that you say have no effect on the "fitness", might well have an effect sooner or later.

Correct. And then they will increase or decrease according to their beneficial or detrimental effect.

 

[holdon]

http://cas.bellarmine.edu/tietjen/Laboratories/evolgame.pdf
http://foru.ms/showpost.php?p=14449626&postcount=5

Is the problem that you have not read these links yet, or that you have read them but don't understand them?

I have not read that stuff.

It doesn't matter if we have a thousand more detrimental mutations than beneficial mutations. Natural selection will act to purify the species of detrimental mutations and distribute beneficial mutations widely.

Let's look at the pepper moth simulation. It begins with supposing that in our sample of moths, the allele for melanism and the allele for absence of melanism are equally distributed. i.e. 50% or 0.5 of the alleles will produce melanism an 0.5 will not. In a standard Hardy-Weinberg distribution this will give you p^2+2pq+q^2 or (0.5*0.5)+2(0.5*0.5)+(0.5*0.5)=0.25MM, 0.5Mm, 0.25mm

M=allele for melanism MM homozygous condition
m=absence of melanism mm=homzygous condition
Mm=heterozygous condition. Since the allele for melanism is dominant, this genotype produces melanism

So 3 out of 4 or 0.75 of the population exhibits melanism.

In the absence of selective pressures, we can predict that these frequencies will be pretty much the same in the next generation.

But look what happens when you get a selection pressure.

This exercise assumes a doubling of the population from one generation to the next. Beginning with 150 moths, they would expect 300 in the next generation. But they simulated some loss due to predation. So they got 240 surviving moths. Had the predation not been selective, we would still get the same proportion of alleles in the 0.25MM+0.5Mm+0.25mm distribution or 60MM+120Mm+60mm individuals among the 240 survivors.

Instead we find 80MM+130Mm+30mm. From this we can calculate the ratio of each genotype as 0.33MM+0.54Mm+0.13mm.

Clearly the frequency p of the M allele has increased at the expense of frequency q of the m allele.

Instead of a 50:50 distribution you now have a 60:40 distribution.

If the selection pressure is maintained, the proportion of M alleles will continue to rise and that of m alleles will continue to fall. If the selection pressure is reversed to favour the m allele you will see the ratios reversing as well.

This is the sort of math I used to show the changing ratios in various scenarios--including one in which the beneficial mutation had to balance off two detrimental mutations. (See second link above.)

I can explain the results in more detail if you wish, but the results clearly show that even when coping with multiple factors, detrimental traits will tend to decrease in frequency while beneficial traits will tend to increase in frequency.

But once this population of moths was submitted to a different environment, they sprung right back to their previous phenotype, no? So, why assume that the environment as a selective force works only in one way? And it is not true that a M:m ratio will continue to increase under a given selection pressure. Consecutive additional pressures in the same direction would be required for every new population to go from a 60:40 to a 70:30 etc. distribution.

Correct. And then they will increase or decrease according to their beneficial or detrimental effect.

I think little is known about non-coding DNA. More and more we learn that they seem to have an influence on the coding segments. It is therefore very likely that mutations in those areas do have an effect. Those areas could possible hold keys as to why certain loci vary ("mutate") and to what extent.

 

[gluadys]

I have not read that stuff.

Why not? Read it and then if you have further questions I'll be happy to field them.

But once this population of moths was submitted to a different environment, they sprung right back to their previous phenotype, no? So, why assume that the environment as a selective force works only in one way?

Whose making that assumption? Did you miss this paragraph in my last post?

If the selection pressure is maintained, the proportion of M alleles will continue to rise and that of m alleles will continue to fall. If the selection pressure is reversed to favour the m allele you will see the ratios reversing as well.​

And it is not true that a M:m ratio will continue to increase under a given selection pressure.

Yes, it is. To get a different result you need to change the selection pressure (which is what happened in the pepper moth scenario).

Consecutive additional pressures in the same direction would be required for every new population to go from a 60:40 to a 70:30 etc. distribution.

No, additional selective pressures are not needed, just additional generations.

Let's follow that last scenario through a few generations.

Each time we will begin with a population of 150 with an expectation of 300 in the next generation. But while we began the first generation with an M:m ratio of 50:50 for each subsequent generation we use the ratio we end up with after selection.

In our second generation, we ended up with a genotype distribution of 80:130:30 out of a surviving population of 240

Applying the same distribution to a population of 150 we get a distribution of 50MM:81Mm:19mm (allowing for rounding to a whole number).

If the population doubled to 300 with no selection we would expect to end up with 100MM:162Mm:19mm

But if we get the same survival values (0.8 for MM, 0.87 for Mm, 0.6 for mm) our actual count is a total population of 244 distributed as 80MM:141Mm:23mm.

Now we repeat using this frequency in our next group of 150. This gives us 49MM:87Mm:14mm

Expected result in a doubled population:
98MM:171Mm:28mm

Actual result at same survival rate:
79MM:151Mm:17mm in a population of 247

Work out the genotypes, determine the number of alleles and you will find that at this point we have moved from a 60:40 ratio to a 65:35 ratio. (The student simulation shows how to do this.) It will take few more generations to get to a 70:30 or higher M:m ratio, but nothing more is needed than the same constant selection pressure in the same direction.

I think little is known about non-coding DNA. More and more we learn that they seem to have an influence on the coding segments.

For natural selection it doesn't really make a difference if the effect is caused directly by coding genes or indirectly by the influence of other genes. Genes are selected indirectly by the impact of natural selection on the expressed character trait. (Birds did not analyse what made some moths easier to see. They just took advantage of the colour as appropriate. The allele selection was an indirect effect of the predation selection.)

It is therefore very likely that mutations in those areas do have an effect. Those areas could possible hold keys as to why certain loci vary ("mutate") and to what extent.

It is true that some regions of the genome appear to mutate more easily than others. But again this is not much of a factor in natural selection except that regions which mutate more easily may offer more options for selection.

 

[holdon]

Why not? Read it and then if you have further questions I'll be happy to field them.



Whose making that assumption? Did you miss this paragraph in my last post?

If the selection pressure is maintained, the proportion of M alleles will continue to rise and that of m alleles will continue to fall. If the selection pressure is reversed to favour the m allele you will see the ratios reversing as well.​

Yes, it is. To get a different result you need to change the selection pressure (which is what happened in the pepper moth scenario).



No, additional selective pressures are not needed, just additional generations.

Let's follow that last scenario through a few generations.

Each time we will begin with a population of 150 with an expectation of 300 in the next generation. But while we began the first generation with an M:m ratio of 50:50 for each subsequent generation we use the ratio we end up with after selection.

In our second generation, we ended up with a genotype distribution of 80:130:30 out of a surviving population of 240

Applying the same distribution to a population of 150 we get a distribution of 50MM:81Mm:19mm (allowing for rounding to a whole number).

If the population doubled to 300 with no selection we would expect to end up with 100MM:162Mm:19mm

But if we get the same survival values (0.8 for MM, 0.87 for Mm, 0.6 for mm) our actual count is a total population of 244 distributed as 80MM:141Mm:23mm.

Now we repeat using this frequency in our next group of 150. This gives us 49MM:87Mm:14mm

Expected result in a doubled population:
98MM:171Mm:28mm

Actual result at same survival rate:
79MM:151Mm:17mm in a population of 247

Work out the genotypes, determine the number of alleles and you will find that at this point we have moved from a 60:40 ratio to a 65:35 ratio. (The student simulation shows how to do this.) It will take few more generations to get to a 70:30 or higher M:m ratio, but nothing more is needed than the same constant selection pressure in the same direction.




For natural selection it doesn't really make a difference if the effect is caused directly by coding genes or indirectly by the influence of other genes. Genes are selected indirectly by the impact of natural selection on the expressed character trait. (Birds did not analyse what made some moths easier to see. They just took advantage of the colour as appropriate. The allele selection was an indirect effect of the predation selection.)



It is true that some regions of the genome appear to mutate more easily than others. But again this is not much of a factor in natural selection except that regions which mutate more easily may offer more options for selection.

But of course all this is begging the question that natural selection occurs in a "progressive way" (so as to generate higher organisms) and that some organisms are perfectly fine (stayed like they were millions of years ago), whereas other higher forms presumably evolved from those, under the same natural environments.

 

[gluadys]

But of course all this is begging the question that natural selection occurs in a "progressive way" (so as to generate higher organisms) and that some organisms are perfectly fine (stayed like they were millions of years ago), whereas other higher forms presumably evolved from those, under the same natural environments.

Not really. The theory of evolution in a strict sense does not cover the pathways of evolution. We can work out from the evidence where current species came from, but for the most part, not where they will go.

There is no program of "progress" built into evolution. For over a billion years, evolution produced nothing but more and more bacteria.

Don't assume the "same" natural environments either. Ecological niches can vary a great deal in virtually the same locality. Some insects, for example, specialize not only in eating certain plants, but certain parts of a plant. Put it on the wrong plant, or the wrong part of a plant within 2 feet of the right one, and it is in a different natural environment, for it.



The other factor is that it is advantageous to diversify rather than have all species follow a similar pathway. Evolution is not like a fixed railway track with species spread out along it in a spectrum of progression. It is more a pattern of branches branching from branches and splitting into more branches. Who is to say what species is more "evolved"?

All we can say is that some are more different visibly from their ancestors than others. That doesn't make those that preserved ancient forms any less evolved. They too are subject to mutations and it takes as much natural selection to preserve a species as to change it.

 

[holdon]

Not really. The theory of evolution in a strict sense does not cover the pathways of evolution. We can work out from the evidence where current species came from, but for the most part, not where they will go.

But even "the evidence" of the origin is not really evidence in my view. It's a theory with many assumptions and according to me with many flaws.

There is no program of "progress" built into evolution. For over a billion years, evolution produced nothing but more and more bacteria.

Has there ever been a thought in evolution theory that more complex organisms might have retrograded into less complex ones by loss of genetic material perhaps? Why is it always assumed that evolution happens from lower to higher?

Don't assume the "same" natural environments either. Ecological niches can vary a great deal in virtually the same locality. Some insects, for example, specialize not only in eating certain plants, but certain parts of a plant. Put it on the wrong plant, or the wrong part of a plant within 2 feet of the right one, and it is in a different natural environment, for it.

Of course in a micro cosmos. But where populations are free to move and free to adapt to whatever over time you would rather see one or a few species that have proven the best adapted to all worlds.

The other factor is that it is advantageous to diversify rather than have all species follow a similar pathway. Evolution is not like a fixed railway track with species spread out along it in a spectrum of progression. It is more a pattern of branches branching from branches and splitting into more branches. Who is to say what species is more "evolved"?

Diversification over time would seize if all selection pressures are equal. Only if they change would the species adapt, evolve if you will. But I agree who is to say what is more evolved, because nobody knows what the "source material" looked like.

All we can say is that some are more different visibly from their ancestors than others. That doesn't make those that preserved ancient forms any less evolved. They too are subject to mutations and it takes as much natural selection to preserve a species as to change it.

But that's exactly the dilemma: if these ancient forms underwent as many mutations as the other newer forms, why did one preserve the old form and did the other go into the new direction? Of course you're going to say: because the selection pressure was different for one from the other. But that means that isolation upon isolation, etc., etc., must have happened for those forms to emerge. Hardly likely for something as ubiquitous as worms, bacteria, etc..

 

[USincognito]

Has there ever been a thought in evolution theory that more complex organisms might have retrograded into less complex ones by loss of genetic material perhaps? Why is it always assumed that evolution happens from lower to higher?

Sort of and it's not. You're projecting value judgements on to a theory that does not contain them. Complexity and advanced are certainly ideas that can be applied, but their tainted by human bias. Most people would say a wildebeast is "more complex" than a bee, but bee society is actually much more "complex" than heard animals like wildebeasts.

And what we would call "advancements" (again, due to human bias) come with tradeoffs. It takes more energy to be a fish than a starfish and being a starfish takes more than being a filter feeder. That's why "retrograde" evolution is actually due to a selective pressure failing to require a structure develop - ex. legs on snakes or eyes in blind cave fish.

They also don't lose the genetic information, they just fail to express it. Snakes still have the genes to make legs, they're just turned off. Blind cave fish still have eyes, but they aren't fuctional.

 

[shernren]

But that's exactly the dilemma: if these ancient forms underwent as many mutations as the other newer forms, why did one preserve the old form and did the other go into the new direction? Of course you're going to say: because the selection pressure was different for one from the other. But that means that isolation upon isolation, etc., etc., must have happened for those forms to emerge. Hardly likely for something as ubiquitous as worms, bacteria, etc..

Since Australians exist, why are the British still around?

Every time a new niche is discovered by life, life radiates into it, and believe me, we have a lot of niches. Furthermore, when new life re-radiates into old niches, it often does so with interesting results. Plankton, mollusks, cephalopods, fish, penguins, sea lions, and whales are all different clades' answers to the same habitat.

Why is this "hardly likely"? Furthermore, not only have you failed to present any evidence whatsoever that this scenario is "hardly likely", you have failed to put forth any evidence that this scenario (life radiating into different niches via evolution) cannot explain, and you have failed to present any alternative scenario that could explain it. This is not how science progresses. Science progresses by:

1. new data;
2. showing that new data cannot be explained by existing theories;
3. proposing new theories that explain this new data;
4. showing how new theories would have led to the existing theories as special cases under restricted conditions.

 

[gluadys]

But even "the evidence" of the origin is not really evidence in my view.

But you opinion is worthless until you have actually looked at the evidence.

It's a theory with many assumptions and according to me with many flaws.

Typically, people who don't understand or know much about evolution make more assumptions about it than those who do. They also tend to assume that conclusions are assumptions. That was the reason for the OP. In school we are often taught the conclusions scientists have come to without being given sufficient information about how they came to that conclusion---how they discovered and tested the evidence.

So we see these apparently unsupported conclusions and assume scientists just plucked them out of thin air because we are not familiar with the research that went into them.

As for flaws, no one claims the theory is flawless, only that it is the best one we have. Most flaws assumed by those not familiar with evolution are not genuine flaws at all, only misunderstanding of how evolution works.

Has there ever been a thought in evolution theory that more complex organisms might have retrograded into less complex ones by loss of genetic material perhaps? Why is it always assumed that evolution happens from lower to higher?

Now here is a good example. You are making an assumption about what scientists assume. But scientists don't make the assumption you assume they do. It is your assumption that is incorrect, not the assumption that scientists don't actually make.

As USIncognito says, often a species that is "simpler" in some way than its ancestors has not lost any genetic material. It is just not being expressed. Now and again you get an atavism--an individual born with the old feature that no longer exists in the species normally. In humans, it occasionally happens that a child is born with a small tail. All human embryos develop a tail, but it disappears well before birth. In a very, very few instances, the programmed death of the embryonic tail does not happen.

Another instance where the descendant is commonly simpler than the ancestor is in parasites. Where you have related organisms and one is a hunter/gatherer while the other is a parasite, the parasite has often dispensed with features in its related species it no longer uses.

Of course in a micro cosmos. But where populations are free to move and free to adapt to whatever over time you would rather see one or a few species that have proven the best adapted to all worlds. Diversification over time would seize if all selection pressures are equal.

More assumptions. Why on earth would all selection pressures have to be equal? And very few species are best adapted to all worlds. Certainly there are generalists that adapt easily to many environments. Our own species is one. Animals that roam the great plains of North America show much less variety than those that inhabit narrow mountain valleys. Simply because the prairie environment itself varies less than the ecology of different mountain valleys.

But that's exactly the dilemma: if these ancient forms underwent as many mutations as the other newer forms, why did one preserve the old form and did the other go into the new direction? Of course you're going to say: because the selection pressure was different for one from the other.

Exactly. What often happens is that part of the population moves into a new territory and experiences a different set of selection pressures. The stay-at-homes maintain the old form and the travellers develop the new form. Both experienced the same rate of mutations, but in the stay-at-homes, who were already well-adapted, new mutations tended to be rejected by natural selection, while in the travellers new mutations might be advantageous.

But that means that isolation upon isolation, etc., etc., must have happened for those forms to emerge.

Yes, though the isolation was not always geographic. There are various forms of sympatric isolation as well.

Hardly likely for something as ubiquitous as worms, bacteria, etc..

But these are not species. They are huge categories of thousands of different species. Bacteria, as a domain, are ubiquitous, but each species of bacteria is not. Many are very specialized in where they can survive.

You, as an individual, may not be able to tell one bacterium from another, but they are a very diverse group of species. The diversity of bacteria rivals that of all the plant and animal species put together.

Worms is a term applied to groups of species in several different phyla of animals. Being in different phyla is about as different as you can get and still be in the same kingdom.

Just think of all the different kinds of worms there are: annelid worms, roundworms, peanut worms, flatworms, nematode worms, horsehair worms---and each of those are again broad categories with many species in each category. Lots and lots of diversity there.

 

[holdon]

Sort of and it's not. You're projecting value judgements on to a theory that does not contain them. Complexity and advanced are certainly ideas that can be applied, but their tainted by human bias. Most people would say a wildebeast is "more complex" than a bee, but bee society is actually much more "complex" than heard animals like wildebeasts.

And what we would call "advancements" (again, due to human bias) come with tradeoffs. It takes more energy to be a fish than a starfish and being a starfish takes more than being a filter feeder. That's why "retrograde" evolution is actually due to a selective pressure failing to require a structure develop - ex. legs on snakes or eyes in blind cave fish.

They also don't lose the genetic information, they just fail to express it. Snakes still have the genes to make legs, they're just turned off. Blind cave fish still have eyes, but they aren't fuctional.

I agree: "advancement" is purely arbitrary. But "evolution" just means that....

 

[holdon]

Since Australians exist, why are the British still around?

Every time a new niche is discovered by life, life radiates into it, and believe me, we have a lot of niches. Furthermore, when new life re-radiates into old niches, it often does so with interesting results. Plankton, mollusks, cephalopods, fish, penguins, sea lions, and whales are all different clades' answers to the same habitat.

Why is this "hardly likely"? Furthermore, not only have you failed to present any evidence whatsoever that this scenario is "hardly likely", you have failed to put forth any evidence that this scenario (life radiating into different niches via evolution) cannot explain, and you have failed to present any alternative scenario that could explain it. This is not how science progresses. Science progresses by:

1. new data;
2. showing that new data cannot be explained by existing theories;
3. proposing new theories that explain this new data;
4. showing how new theories would have led to the existing theories as special cases under restricted conditions.

How do you want me to explain your theory of "life radiating into different niches via evolution" if I don't subscribe to that theory? You're positing something that still needs to confirmed. If you wear red glasses all you will see is things in red. The things themselves don't change, but your opinion of them. So, with this supposed evolution theory: everything is explained in that light, because you think it is thus.
How then do scientists who all wear the same kind of glasses know things? (see OP).

 

[holdon]

But you opinion is worthless until you have actually looked at the evidence.

Well, opinion is worthless if indeed "the evidence" is portrayed and interpreted because of certain underlying beliefs.

Typically, people who don't understand or know much about evolution make more assumptions about it than those who do. They also tend to assume that conclusions are assumptions. That was the reason for the OP. In school we are often taught the conclusions scientists have come to without being given sufficient information about how they came to that conclusion---how they discovered and tested the evidence.

So we see these apparently unsupported conclusions and assume scientists just plucked them out of thin air because we are not familiar with the research that went into them.

But it's not that we don't know anything about them (scientists) or their conclusion or their theories.

As for flaws, no one claims the theory is flawless, only that it is the best one we have. Most flaws assumed by those not familiar with evolution are not genuine flaws at all, only misunderstanding of how evolution works.

That may be right. But when the thing itself is elevated as religious dogma beyond all contest, it doesn't matter anymore what flaws we find, because the belief that it is true exists.

Now here is a good example. You are making an assumption about what scientists assume. But scientists don't make the assumption you assume they do. It is your assumption that is incorrect, not the assumption that scientists don't actually make.

Well, the very word "evolution" means that. And show me "a scientist" that doesn't believe that.

As USIncognito says, often a species that is "simpler" in some way than its ancestors has not lost any genetic material. It is just not being expressed. Now and again you get an atavism--an individual born with the old feature that no longer exists in the species normally. In humans, it occasionally happens that a child is born with a small tail. All human embryos develop a tail, but it disappears well before birth. In a very, very few instances, the programmed death of the embryonic tail does not happen.

And why "programmed death"? Is there any evidence that "having a tail" is detrimental for "fitness"? And if so, where is it?

Another instance where the descendant is commonly simpler than the ancestor is in parasites. Where you have related organisms and one is a hunter/gatherer while the other is a parasite, the parasite has often dispensed with features in its related species it no longer uses.

But in all these supposed "examples" you don't know what the "source population" was like. How complex or not it was. It's hypothesis upon hypothesis.

More assumptions. Why on earth would all selection pressures have to be equal? And very few species are best adapted to all worlds. Certainly there are generalists that adapt easily to many environments. Our own species is one. Animals that roam the great plains of North America show much less variety than those that inhabit narrow mountain valleys. Simply because the prairie environment itself varies less than the ecology of different mountain valleys.

Because some species apparently never changed.

Exactly. What often happens is that part of the population moves into a new territory and experiences a different set of selection pressures. The stay-at-homes maintain the old form and the travellers develop the new form. Both experienced the same rate of mutations, but in the stay-at-homes, who were already well-adapted, new mutations tended to be rejected by natural selection, while in the travellers new mutations might be advantageous.



Yes, though the isolation was not always geographic. There are various forms of sympatric isolation as well.



But these are not species. They are huge categories of thousands of different species. Bacteria, as a domain, are ubiquitous, but each species of bacteria is not. Many are very specialized in where they can survive.

But many others are. The whole problem with explaining that natural selection makes sure species change constantly is that there is virtually no evidence (to come back to that word) that it wipes out gene information and ensuring new information comes along. Natural selection explains everything, but therefore it explains nothing. Take your example of the pepper moth: apparently not much changed. It was still the same moth before and after, and nobody is to tell what was before and what was after.