Questions on speciation

[chilehed]

First of all, this is all irrelevant to the question of the existance of God, which is a discussion of philosophy and history rather than science. By definition, it’s impossible to detect the unmoved first mover in the lab.

I'm not convinced that scripture demands belief in a creation period of six 24-hour days.

I'm also not convinced that evolutionary theory has plausible answers to the difficulties that have been pointed out in it, although I must admit that I'm not as well-versed in the details of evolutionary theory as I ought. I've reviewed the transcripts of a couple of creation/evolution debates (one a running on-line thing, the other from a debate at Auburn University about 10 years ago), and although in both instances the evolutionists soundly trounced the creationists, it was as much due to the unpreparedness of the creationists as it was due to the strength of the evolutionist’s arguments.

Could someone help me by clarifying a couple of things?

First, points of definition:

What do we all agree what “speciation” is? I’d say that the term has to include the idea that the new organism cannot back-cross to the parent(s), and is fertile.

What is a “point mutation”? Sometimes I hear the term used to indicate that there has been a mutation in a single gene (single nucleotide or multiple nucleotides?). I also have heard it used to indicate that a dramatic change to the offspring has occured in a single generation, which may be due to the mutation of multiple genes. I’ve gathered that the quarrel over whether or not we’ve found transitional forms stems from a point of semantics: evolutionists are willing to accept as a transitional form something that has had changes to multiple structures, while creationists look at the same changes and say that they could not have been due to a single genetic change and are irreducibly complex.

Whatever definition is correct, are there any well-documented cases of a point mutation resulting in selectable offspring that end up as viable new species populations?

Second, I’ve seen lists of documented speciation. Most of them (all the ones I managed to wade through) were intergeneric hybrids of various plants which, although they could not be back-crossed with the parent plants, were also sterile. These don’t seem to me to be very hopeful prospects for selection.

Are there any documented cases of speciation from intergeneric hybrids?

Please correct any assumptions that may underlie my questions, if need be.

Unfortunately, I don’t get to monitor this site constantly, so bear with me if it takes me a day or two to re-post.

Thanks.

and, my oh my, many blessings in return to whoever loaded me up.

 

[Late_Cretaceous]

Read the following:
http://www.talkorigins.org/faqs/faq-speciation.html

It has documented/observed instances of speciation in a surprisingly large number of organisms. Cases where speciation has occured in insects may be particularly interesting to you.

 

[lucaspa]

What do we all agree what “speciation” is? I’d say that the term has to include the idea that the new organism cannot back-cross to the parent(s), and is fertile.

For sexually reproducing organisms, species are defined as:

"A species is a group of individuals fully fertile inter se, but barred from interbreeding with other similar groups by its physiological properties. (producing either incompatibility of parents, or sterility of the hybrids, or both). (Dobzhansky 1935)

Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. (Mahr 1942) "

As long as the groups DO NOT interbreed they are separate species. There are several mechanisms to be reproductively isolated and we can go into them if you want.

What is a “point mutation”?

A point mutation is a change in ONE nucleotide. It is usually a substitution, say an A for a G or T for a C.

I’ve gathered that the quarrel over whether or not we’ve found transitional forms stems from a point of semantics: evolutionists are willing to accept as a transitional form something that has had changes to multiple structures, while creationists look at the same changes and say that they could not have been due to a single genetic change and are irreducibly complex.

I haven't heard that one before. Creationists usually demand that EVERY feature be intermediate between the ancestor and descendent, while evolutionists say that transitionals are mosaics, having some features of the ancestors and some of the descendents.

Whatever definition is correct, are there any well-documented cases of a point mutation resulting in selectable offspring that end up as viable new species populations?

A single point mutation? I'll look. Speciation usually requires the ACCUMULATION of a number of changes over a period of many generations.

Second, I’ve seen lists of documented speciation. Most of them (all the ones I managed to wade through) were intergeneric hybrids of various plants which, although they could not be back-crossed with the parent plants, were also sterile.

Here are three examples that are fertile but can't be back crossed:
2. Speciation in action Science 72:700-701, 1996 A great laboratory study of the evolution of a hybrid plant species. Scientists did it in the lab, but the genetic data says it happened the same way in nature. Follow up paper in PNAS http://www.pnas.org/cgi/content/full/95/20/11757
2a. Hybrid speciation in peonies http://www.pnas.org/cgi/content/full/061288698v1#B1
2c. http://www.holysmoke.org/new-species.htm new species of groundsel by hybridization

Are there any documented cases of speciation from intergeneric hybrids?

There is a wheat-rye hybrid, but I'm not sure if that is between two genera. I would be surprised if such did happen. After all, genera are two groups of species. They may or may not have had a common ancestor (depends on which genera they are) but the divergence from the common ancestor makes it unlikely that a species from genus A would be able to hybridize with a species from genus B.

BTW, speciation by hybridization happens mostly in plants but only very rarely in animals.

 

[Jet Black]

BTW, speciation by hybridization happens mostly in plants but only very rarely in animals.

is that just because of the complexity of the oganism then? or something in the reproductive process itself (i.e. the way the gametes fuse) or.. a mix of the above?

 

[JohnR7]

First of all, this is all irrelevant to the question of the existance of God, which is a discussion of philosophy and history rather than science. By definition, it’s impossible to detect the unmoved first mover in the lab.

If there were no God, then there would be no science. God created everything and without a creator there would be nothing for science to study. Not to mention that there would be no scientist, because God created people also.

 

[Jet Black]

assuming you believe in God, of course.

 

[JohnR7]

assuming you believe in God, of course.

According to the gallop polls between 90% & 95% of the people believe in God. The longer people live, the more they tend to believe.

 

[Vance]

The longer people live, the more they tend to believe.

The closer you get to death, the more you believe there is something on the other side.

I agree that there *is* something on the other side, of course, but this phenomenon can not be ignored.

 

[chilehed]

let's NOT turn this thread into a debate on the existance of God - I mentioned that it's irrelevant exactly because it's a separate discussion. If I had wanted to discuss the philosophical proofs for God's existance, I would have gone to a different forum and begun with Aristotle.

Thanks for the replies on speciation, I'll check out the links and get back ASAP.

 

[chilehed]

Those are some very interesting links, lots to wade through plus I’m not familiar with many of the technical terms.
I’m not convinced of the validity of the assortative mating model of speciation. Sure you can breed flies so that they can’t mate because of behavioral or physical differences, so what? You couldn’t get a Great Dane to mate with a Chihuahua, but that doesn’t make them two species. And human cultures exhibit behavioral (and physical) differences large enough to inhibit mating, but that doesn’t mean that I’m a different species than some of the people that live in Africa. Did I miss something?

I do find some of the speciation events involving plants to be rather more compelling, assuming that the work is valid (there’s that pesky faith thing again!). Radish leaves and cabbage roots - must’ve been a frustrating day at the office!

I’m wondering about the percentages involved in passing on point mutations as they accumulate, but I still haven’t come to a sufficiently elegant way of asking my question. Assume a speciation event based on the accumulation of 10 point mutations. It seems to me that one in one million offspring will express all 10 mutations, but one in three will express nine or less. If all ten mutations are needed, then this 33% will be less likely to survive than the parents. So the model requires that the parent specie go into decline before the new specie is expressed, right? And to establish a viable population, you need quite a number of sufficiently unreleated new individuals to get past the issues of inbreeding.

What am I missing?

 

[Jet Black]

Those are some very interesting links, lots to wade through plus I’m not familiar with many of the technical terms.
I’m not convinced of the validity of the assortative mating model of speciation. Sure you can breed flies so that they can’t mate because of behavioral or physical differences, so what? You couldn’t get a Great Dane to mate with a Chihuahua, but that doesn’t make them two species. And human cultures exhibit behavioral (and physical) differences large enough to inhibit mating, but that doesn’t mean that I’m a different species than some of the people that live in Africa. Did I miss something?

dogs are an odd case because their evolution has been forced and very strongly selected. Give them a few thousand years and danes will be a different species to chihuauas because of the totally isolated gene pools picking up different mutations. same for humans, it's just about isolated gene pools.

I’m wondering about the percentages involved in passing on point mutations as they accumulate, but I still haven’t come to a sufficiently elegant way of asking my question. Assume a speciation event based on the accumulation of 10 point mutations.

there are sometimes "events" in the case of hybridisation and so on, but most speciations aren't events, they are the result of slow accumulation of mutations in isolated gene pools.

 

[Osiris]

If there were no God, then there would be no science. God created everything and without a creator there would be nothing for science to study. Not to mention that there would be no scientist, because God created people also.

hmmm...
let's assume that there is a God, science is here, well, he created it...
let's assume that there is no God, hey, there's still science here!

if God did or didn't exist, everything how it is now would still be here, because there are 2 possibilities, God & no God... we dont know which 1 is true, but either way we are still here. What I see that you are trying to do is define a word using the same word in the definition.

jump = when someone jumps

God exists because God created us...

God's Existance = G = ?
Our Existance = x = true

(this was the outcome of life)
if G = ? then x = true

all we have to do is solve for G, not for x

 

[lucaspa]

is that just because of the complexity of the oganism then? or something in the reproductive process itself (i.e. the way the gametes fuse) or.. a mix of the above?

Mostly the mating. Most animals have fairly rigorous mating procedures and usually the male has to insert his reproductive organ into the female. There are lots of signals and behaviors to see that this does not happen to the wrong species.

However, a lot of plants simply put pollen on the wind or water and it can blow into any old plant's female receptical. And so you can easily get pollen of one species fertilizing another.

 

[lucaspa]

Those are some very interesting links, lots to wade through plus I’m not familiar with many of the technical terms.

Then by all means ask and I'll explain the technical terms to you until you understand.

I’m not convinced of the validity of the assortative mating model of speciation. Sure you can breed flies so that they can’t mate because of behavioral or physical differences, so what? You couldn’t get a Great Dane to mate with a Chihuahua, but that doesn’t make them two species.

Actually, for the Great Dane and chihuahua it does. What is important is that the gene pools are separate. If that comes about by genetic incompatibility or by refusing to mate, the result is the same. The two populations are genetically separate and go their separate ways.

And human cultures exhibit behavioral (and physical) differences large enough to inhibit mating, but that doesn’t mean that I’m a different species than some of the people that live in Africa. Did I miss something?

It means you will be someday. Speciation is not a quick event that takes place within a generation. It is a long, slow process and, while you are in the midst of it, there is no hard and fast line to say that NOW! BAM! there is a new species. Say the process takes a thousand generations. At generation 1 we know the population is 1 species and at generation 1,000 we can definitely see there are 2 species. But at generation 499 are they one or two species? There's a huge gray area there where, if there is gene flow (mating) between the populations, speciation could stop.

Once mating is stopped, any changes that happen to one population won't happen to the other -- no breeding to bring those changes to the other population. So the populations continue to diverge, each accumulating different changes. Eventually, those changes will be enough so that there is complete genetic incompatibility.

The !Kung in the Kalahari desert have alleles (forms of a gene) that no other population on earth has. What's more, they are missing alleles that everyone else has. Genetic studies show that there is some gene flow out of the !Kung. That is, !Kung males and females marry outside the population. But then they must live outside the !Kung. So there is no gene flow into the !Kung. If the process continues for another 500 generations, you and I will belong to one species and the !Kung to another.

I’m wondering about the percentages involved in passing on point mutations as they accumulate, but I still haven’t come to a sufficiently elegant way of asking my question. Assume a speciation event based on the accumulation of 10 point mutations. It seems to me that one in one million offspring will express all 10 mutations, but one in three will express nine or less.

This is where you are missing selection and how it cuts down all those odds.

Now, two populations are separated and Population A is under different selection pressure. Mutation 1 appears. It helps survival. That means that in several generations (depending on the size of the population and how severe the selection pressure is) everyone will have mutation 1. Then mutation 2 appears. Same thing happens. Everyone now has mutations 1 and 2 when mutation 3 appears. And so on. Suddenly your odds of 1 in a million disappers.

If all ten mutations are needed, then this 33% will be less likely to survive than the parents.

Notice that you changed the goalposts here. Accidentally, but you changed them. You started off saying you needed a total of 10 mutations for speciation. Now you say you need all 10 mutations right now for survival. Different things altogether.

Each mutation will aid survival in comparison to the individuals without the mutation. Remember that "in comparison" Without the mutation, the individual survives as long as it doesn't have to compete with an individual with the mutation. You see, the competition is relative, not absolute.

Let me give you an analogy. Say both of us are running from an angry bear. To survive I don't have to outrun the bear. I just have to outrun you.

So the model requires that the parent specie go into decline before the new specie is expressed, right?

Not at all.

There are 3 ways this works.
1. The whole population transforms over time into a new species. There was one species and now there is still one species. However, if you had a time machine and took the now population back to breed with the past population, they wouldn't be able to.

2. The populations are separated geographically. Each population does just fine in its location, but each location has a different environment and therefore each population accumulates different changes. So, if and when the populations meet again, you have two species where there used to be one.

3. The populations are separated by habitat and how they earn a living. This has been observed with insects. A population of insects that uses one type of fruit -- crabapples, will be colonize a jonathan apple tree. They have a slightly different environment. So now the insects on the crabapple and the jonathan apple trees are close geographically, but they don't associate with each other much. Changes occur because crabapples are similar to, but not identical to, jonathan apples. After a while the changes accumulate and you have two species where there was one.

And to establish a viable population, you need quite a number of sufficiently unreleated new individuals to get past the issues of inbreeding.

No. It turns out that any two unrelated individuals between them have about 75% of the genetic diversity of the whole population. Since incest is a social taboo not a biological one, siblings of the first pair can mate. Yes, you lose some to combining lethal recessives but, hey, thems the breaks. Now, in the first couple of generations (depending on how many offspring in each generation) there is the danger of losing the colony due to accident. While there are only 2, having one killed pretty much louses up the whole thing.

So, the problem is not genetics, but simply accidents wiping out the population before there are enough of them so that accidents won't wipe out everyone. Which is why the Founder Effect (1 -5 breeding pairs) is pretty rare for speciation. Usually there are more than 5 breeding pairs involved.

 

[Cantuar]

What do we all agree what “speciation” is? I’d say that the term has to include the idea that the new organism cannot back-cross to the parent(s), and is fertile.

Speciation doesn't tend to take place in one generation like that. It's more gradual and involves whole populations, not individuals. What you've described wounds more like saltation (involving Richard Goldschmidt's hopeful monster) than like a viable evolutionary process.

 

[Philostratus]

sorry, posted in wrong thread.

 

[Plan 9]

Those are some very interesting links, lots to wade through plus I’m not familiar with many of the technical terms.
I’m not convinced of the validity of the assortative mating model of speciation. Sure you can breed flies so that they can’t mate because of behavioral or physical differences, so what? You couldn’t get a Great Dane to mate with a Chihuahua, but that doesn’t make them two species. And human cultures exhibit behavioral (and physical) differences large enough to inhibit mating, but that doesn’t mean that I’m a different species than some of the people that live in Africa. Did I miss something?

I honestly think you may be underestimating the prowess of the Chiuahua in your first example.

What behavioral and physical differences in human cultures did you have in mind in the second?

 

[Plan 9]

[/font]
The !Kung in the Kalahari desert have alleles (forms of a gene) that no other population on earth has. What's more, they are missing alleles that everyone else has. Genetic studies show that there is some gene flow out of the !Kung. That is, !Kung males and females marry outside the population. But then they must live outside the !Kung. So there is no gene flow into the !Kung. If the process continues for another 500 generations, you and I will belong to one species and the !Kung to another.

Where can I find out more about the !Kung, please?

Each mutation will aid survival in comparison to the individuals without the mutation. Remember that "in comparison" Without the mutation, the individual survives as long as it doesn't have to compete with an individual with the mutation. You see, the competition is relative, not absolute.

Let me give you an analogy. Say both of us are running from an angry bear. To survive I don't have to outrun the bear. I just have to outrun you.

This is the best analogy explaining this that I've ever heard!

No. It turns out that any two unrelated individuals between them have about 75% of the genetic diversity of the whole population. Since incest is a social taboo not a biological one, siblings of the first pair can mate. Yes, you lose some to combining lethal recessives but, hey, thems the breaks. Now, in the first couple of generations (depending on how many offspring in each generation) there is the danger of losing the colony due to accident. While there are only 2, having one killed pretty much louses up the whole thing.

So, the problem is not genetics, but simply accidents wiping out the population before there are enough of them so that accidents won't wipe out everyone. Which is why the Founder Effect (1 -5 breeding pairs) is pretty rare for speciation. Usually there are more than 5 breeding pairs involved.

People are always talking about needing a large group of individuals to reestablish a population because oterwise the gene pool will be too small?

 

[David Gould]

I have heard that the current leopard population appears genetically to stem from one pair that survived the last ice age. (It could even have been a pregnant female that survived the last ice age)

 

[David Gould]

http://members.tripod.com/JaguarLady35/cheetahs_the_mighty_sprinters.htm

It is actually cheetahs, not leopards.