Statements About Evolution

[DialecticSkeptic]

Only on paper, I take it?

Obviously. We have multiple streams of empirical evidence pouring in that needs a scientific explanation. Where else would you expect to find that scientific explanation?

 

[Mark Quayle]

Let me phrase it another way.

Let's say I have a gene for x-ray vision (we'll call it the X-gene), and let's say that my husband doesn't. When I fell pregnant with my daughter, she would have a 50% chance of getting the X-gene. We can't be sure until we either do a genetic test or we just wait and see if she can see through walls.

The dominant and recessive stuff is closely related to this topic. Eye colour is a good example. Genes can come in different versions, called "alleles." You have genes for eye colour, and two of the alleles are a brown eye allele, and a blue eye allele.

I have blue eyes, and my mother did too. My father has brown eyes. Brown eyes are a dominant trait. Each person has two copies of the gene for eye colour, one from their mother and one from their father. In the diagram below, a gene for brown eyes is denoted with a "B", while the gene for blue eyes is a "b".

With a dominant gene, if you have one copy, you will have the trait. With eye colour, brown eyes are the dominant trait. So, if your eye colour gene combination is Bb, then the B (being dominant), will override the b, and the person will have brown eyes.

In the first chart, both parents have one of each, so they both have blue eyes. Let's say the mother is along the top, and the father is down the side. You can see that both the mother and the father have Bb genes, so they each have brown eyes. They each have a copy of the blue eye allele, but since they also each have the dominant brown eye allele, that overrides the blue, and they each have brown eyes.

When they procreate, half of their genes each go to their offspring (the different ways the genes can combine are represented by the squares in the middle. In the top left square, we see what would happen if the mother (on the top) provides her B allele and the father provides his B allele. The offspring will have the gene combination BB, which is two genes for brown eyes. So their child in this case will have brown eyes.

But when we look at the top right square in the first example, we see that the mother provides a b allele, the recessive blue eye gene. But the father still provides his dominant B allele. With a gene combination of Bb, the offspring has a dominant brown eye gene which overrides the blue eyed allele, and so the offspring will again have brown eyes. However, in this case they still carry an allele for blue eyes which might get passed along when they have children.

Pretty much the same thing happens in the lower left square, although this time the father is providing the b gene and the mother is providing the B gene.

In the lower left square, both parents provide the recessive b allele, and since this offspring only gets the b alleles, they will have blue eyes.

The second example is what happened with my parents (which is why I proposed that the mother is represented by the top). My mother had blue eyes, so she could not have had a B allele (since if she did, it would have given her brown eyes, since it is the dominant version). So she must have had the bb combination. I can also figure out that my father had a Bb combination. After all, if his combination was BB, then I MUST have received a B allele from him, and since that is the dominant allele, I would have had brown eyes. So I must have got a b allele from him, plus one of my mother's two b alleles, thus giving me bb as well.

View attachment 319844

Let's say the mother and father are both Bb. The offspring will "be" BB, as you say. What happened to the b from each? They are not present in that genetic makeup of that offsping?

 

[Mark Quayle]

The definition of "species" is a rather difficult one. It's typically defined as a group of individuals who can produce fertile offspring. So all the different kinds of dogs are considered the same species, since you can breed a Dalmatian and a German Shephard and the puppies will be fertile themselves. But the example you used a while back with horses and donkeys producing mules, well, since mules themselves are sterile, then horses and donkeys are considered different species.

But it all depends on how closely related two groups are. Let's say you have a population, and they are divided for some reason. Let's say that a river changes course during a flood, and now you have two groups, one on each side of the river, and they can't interbreed any more. Each population will now evolve in their own way, and since conditions on the different sides may be different, the two different populations will evolve to suit the unique pressures they face, and thus they will gradually become more and more different.

If you come back ten years after the separation and take a female from the north side and a male from the south side, they'd probably still be able to interbreed. That wouldn't be enough time for them to evolve apart enough to make them different species. But if you come back a thousand years later, you could find that there's more trouble getting them to breed successfully. And if you came back a million years after, you'd probably find they wouldn't be able to interbreed at all.

But there's no one point where it stops being Species A and becomes Species B. Even if we look at a single population and consider individuals who are isolated not by space, but by time, we'd see the same thing. You could follow a group of animals and watch as they evolve over a million generations. G1 would be able to breed with G2 (and several generations down the line too). G15 would be able to interbreed with both G14 and G16. G165,287 would be able to interbreed with G165,286 and G165,288. But you would likely find that G165,287 could NOT breed with G1. Even though each generation changes only slightly, those slight changes all add up. Over a small number of generations, those changes are not enough to prevent successful breeding, but over many generations, those changes can be enough to prevent it.

So, to get back to your question, the tuskless variant wouldn't be considered a separate species, For that to happen, the tuskless elephants would need to be different enough from the tusked elephants that interbreeding could not produce fertile offspring.

So for the TOE to demonstrate that the heffalump is related to the mastodon, don't they need to show the many steps between?

 

[Shemjaza]

Let's say the mother and father are both Bb. The offspring will "be" BB, as you say. What happened to the b from each? They are not present in that genetic makeup of that offsping?

Exactly.

Passing on genes in particular and evolution in general is about statistical likelihood.

So for the TOE to demonstrate that the heffalump is related to the mastodon, don't they need to show the many steps between?

Counting steps is a pretty arbitrary concept anyway.

Two similar fossils could represent either two extremes of variation of one species that slowly changed over a long period of time and distance... or they could represent two separated populations that continued to vary simultaneously.

 

[Kylie]

Let's say the mother and father are both Bb. The offspring will "be" BB, as you say. What happened to the b from each? They are not present in that genetic makeup of that offsping?

Not quite.

If both parents are Bb, then there are different possible outcomes.

If the offspring gets B from the mother and B from the father, then the offspring will be BB and will have brown eyes because it has two copies of the dominant B allele.

If the offspring gets B from the mother and b from the father, then the offspring will be Bb and will have brown eyes because it has a dominant B allele which overrides the recessive b allele.

If the offspring gets b from the mother and B from the father, then the offspring will be bB and will have brown eyes because it has a dominant B allele which overrides the recessive b allele.

If the offspring gets b from the mother and b from the father, then the offspring will be bb and will have blue eyes because it has only the recessive b allele.

So, out of the four options, there's one chance in four it will have BB, two chances in four that it will have one of each (either Bb or bB), and only one chance in four it will have bb and be blue eyed.

 

[Kylie]

So for the TOE to demonstrate that the heffalump is related to the mastodon, don't they need to show the many steps between?

They don't need to show every single step between the two. There are ways of examining the genetic code of two animals and determining how closely they are related, but that gets very complicated, and I'm not that familiar with it.

 

[Mark Quayle]

Not quite.

If both parents are Bb, then there are different possible outcomes.

If the offspring gets B from the mother and B from the father, then the offspring will be BB and will have brown eyes because it has two copies of the dominant B allele.

If the offspring gets B from the mother and b from the father, then the offspring will be Bb and will have brown eyes because it has a dominant B allele which overrides the recessive b allele.

If the offspring gets b from the mother and B from the father, then the offspring will be bB and will have brown eyes because it has a dominant B allele which overrides the recessive b allele.

If the offspring gets b from the mother and b from the father, then the offspring will be bb and will have blue eyes because it has only the recessive b allele.

So, out of the four options, there's one chance in four it will have BB, two chances in four that it will have one of each (either Bb or bB), and only one chance in four it will have bb and be blue eyed.

Ok, let's say both parents are Bb. I guess my question is not quite whether the offspring will 'have', as in demonstrate, the dominant brown eyes or recessive blue eyes, but whether, supposing it to 'be' or 'have' BB brown eyes, does it then have any b it inherited to contribute to the possibility of blue eyes to future generations.

I hear about some species that have been used as demonstration of current evolution, but the creationists say that, no it is only an ability that species has to adapt to its environment, that is just as easily changed back to its 'original' form, when the environment changed back to its 'original' configuration, and we have seen it happen within our lifetimes.

Not saying this is relevant, but my thinking is along these lines. Out of 5 boys in my family, one doesn't really look much like the other four, but he's almost the spitting image of my grandfather on my dad's side at his age. Another of us doesn't have my dad's personality, but he does have my grandfather's personality.

 

[Mark Quayle]

They don't need to show every single step between the two. There are ways of examining the genetic code of two animals and determining how closely they are related, but that gets very complicated, and I'm not that familiar with it.

I don't know if it really means anything, but:

Chimpanzee: 96 percent identical. By studying the genomes of chimps (which after bonobos are our closest living ancestors), researchers are hoping to understand what makes us uniquely human.

Banana: more than 60 percent identical. ...

If the fact that chimps are 96 percent identical means anything, I would have expected bananas to a lot less identical than 60 percent.

Vegapharm » How genetically related are we to bananas?

 

[Shemjaza]

I don't know if it really means anything, but:

Chimpanzee: 96 percent identical. By studying the genomes of chimps (which after bonobos are our closest living ancestors), researchers are hoping to understand what makes us uniquely human.

Banana: more than 60 percent identical. ...

If the fact that chimps are 96 percent identical means anything, I would have expected bananas to a lot less identical than 60 percent.

Vegapharm » How genetically related are we to bananas?

That's an odd article and I'm curious by what metric they are comparing genes because those number look seriously suspect.

Chimps and humans are life, animals, vertebrates, mammals, primates, apes
Chickens are life, animal, vertebrate
Fruit flies are life, animal

Banana are alive... but they don't even have the same cell structure as animals.

It's possible they are measuring difference in an odd way, or only measuring a particular section of DNA.

For example are these two sequences 90% or 10% identical:
AGATTACTGA
ATGATTACTGA

 

[Kylie]

Ok, let's say both parents are Bb. I guess my question is not quite whether the offspring will 'have', as in demonstrate, the dominant brown eyes or recessive blue eyes, but whether, supposing it to 'be' or 'have' BB brown eyes, does it then have any b it inherited to contribute to the possibility of blue eyes to future generations.

I hear about some species that have been used as demonstration of current evolution, but the creationists say that, no it is only an ability that species has to adapt to its environment, that is just as easily changed back to its 'original' form, when the environment changed back to its 'original' configuration, and we have seen it happen within our lifetimes.

Not saying this is relevant, but my thinking is along these lines. Out of 5 boys in my family, one doesn't really look much like the other four, but he's almost the spitting image of my grandfather on my dad's side at his age. Another of us doesn't have my dad's personality, but he does have my grandfather's personality.

Everyone has two alleles for their eye colour. Which one is passed to the offspring is random. If a person has Bb, then it's random whether it's the B or the b that gets passed. If a person has BB, then they don't have a b to pass on. That, of course, doesn't mean that their descendants can't have blue eyes.

Let's say there's a person (Let's call him John) with BB alleles, and they procreate with an individual with a b allele (either Bb or bb). No matter what, the offspring is going to get a B from John, so John's child is going to get a dominant B allele and thus will have brown eyes. But, there is a chance that John's child will have a recessive b allele, since their mother has a b allele. So even though John's child will have brown eyes due to the dominant B allele, they can still carry the recessive b allele which they can pass onto their offspring, John's grandchild. And if John's child reproduces with someone who has a b allele, then John's grandchild could inherit the b allele from both of their parents, and thus have blue eyes.

Of course, eye colour is rather more complicated than that, since any particular trait has many genes that can affect it, and a single gene can play a part in changing many different traits.

For example, it would seem that, from what I've said, two blue eyed parents can't possibly have a child with brown eyes. After all, if the child had brown eyes, they must have at least one B allele in there, but if either of the parents had a B allele, they wouldn't be blue eyed! But such things can happen. There are some genes that are able to deactivate other genes. So if a parent has Bb alleles, but they also have a gene that deactivates the B allele, then it would be as if that B allele wasn't there at all. But they could still pass the B to their offspring. And if the offspring doesn't have the B-deactivator gene, then they have a fully working B allele, and they'll have brown eyes.

Here's a website with some more information: If both parents have blue eyes, how could they have a child with brown eyes?

 

[Kylie]

I don't know if it really means anything, but:

Chimpanzee: 96 percent identical. By studying the genomes of chimps (which after bonobos are our closest living ancestors), researchers are hoping to understand what makes us uniquely human.

Banana: more than 60 percent identical. ...

If the fact that chimps are 96 percent identical means anything, I would have expected bananas to a lot less identical than 60 percent.

Vegapharm » How genetically related are we to bananas?

It's better to think of DNA as a recipe rather than as a book.

Whereas with a book, you could say, "Sixty percent of this book's text is also found in this other book, so they must be similar," you can easily have two recipes that have sixty percent of the stuff the same, but still end up as very different dishes.

In any case, when someone says that two organisms are X% identical, it's meaningless unless they say what they are measuring. An analogy with words will illustrate.

I can write the sentence:

THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG.

And that's all well enough.

But let's say I change it to:

THE QUICK BROWN FOX JUMPS OVER THE LAZY CAT.

How many changes did I make? You could argue that I only made one change, since only one word is different. But you could also argue that I made three changes, since three letters are different.

And what if I insert a new word (genes can be inserted into new places quite easily. For example, genes can duplicate, and then one of them can gradually evolve to be something else).

THE QUICK BROWN FOX JUMPS HIGH OVER THE LAZY DOG.

How many changes there? You could argue that there is one change (there is one new word, everything else is the same), there are five changes (there are four new letters and one new space inserted), but there is also another way of looking at it. Let's write both sentences, one above the other, and I'll number each position.

Now, How different is this? It's all the same up to position 26, but position 27 is different, so is position 28, position 29, position 30, position 32 and all the way up to position 48. From position 27 to position 48, there are 21 places, and fully 19 of them are different!

So it can be a bit confusing when people talk about how different two organism's genetics are, and this is why different sources can have very different figures.

 

[Kylie]

@Mark Quayle let's move on. In statement 3, I spoke of how parents pass their genes on to their offspring. We've already covered this a fair bit, what with the different allele's for eye colour and such, so may I assume you have no reservations about that?

Anticipating that you will have no reservations, let's also cover Statement 4, where I said that different traits can influence how well the individual animal that has them survives. Do you have any reservations regarding that statement?

 

[Kylie]

Let's say the mother and father are both Bb. The offspring will "be" BB, as you say. What happened to the b from each? They are not present in that genetic makeup of that offsping?

I think you misunderstood.

If the mother and father are Bb, then there are several different ways that the genes can be passed to the offspring.

1. The mother could pass on her B, and the father could pass on his B. In this case, the offspring will be BB and will have brown eyes.
2. The mother could pass on her B, and the father could pass on his b. In this case, the offspring will be Bb and will have brown eyes (since the dominant B allele from the mother overrides the recessive b allele from the father).
3. The mother could pass on her b, and the father could pass on his B. In this case, the offspring will be bB and will have brown eyes (since the dominant B allele from the father overrides the recessive b allele from the mother).
4. The mother could pass on her b, and the father could pass on his b. In this case, the offspring will be bb and will have blue eyes.

Which of these four different results will occur is random, since the allele that the mother passes on is random, as is the allele the father passes on. Each parent has two alleles for themselves (for example, I know I am either bb, or I am Bb with a gene that "cancels out" my B, since I have blue eyes). But I only passed one of them to my daughter.

 

[Kylie]

So for the TOE to demonstrate that the heffalump is related to the mastodon, don't they need to show the many steps between?

No. We could each do a DNA test and find out how closely related we are. Chances are we are not closely related at all. But, if we were to go back far enough, we would be able to find a person who is in my family tree and your family tree as well. This person probably lived several hundred years ago, of course. But we could determine approximately how many generations ago we shared this common ancestor. We would not need to trace every single descendant of that common ancestor on both sides in order for us to know approximately when they existed.

When it comes to different species, we can also look at shared traits. For example, let's say feathers (I'm just coming up with an example off the top of my head here). We might look at a hummingbird and an eagle and say that they are two species that are not closely related (in other words, saying their common ancestor lived a long time ago). But we can be quite sure that whenever this common ancestor lived, it was after the line had evolved feathers. I mean, let's assume that the common ancestor lived BEFORE feathers evolved. Then we'd have to assume that the eagle line evolved feathers after the line diverged, and the hummingbird line evolved the exact same trait completely independently in the same time. When you look at the similarities between feathers of hummingbirds and eagles, the chances of feathers evolving twice and being what we find in nature are absolutely miniscule. it's far more reasonable to say that the ancestor evolved feathers BEFORE the two different lines diverged.

Let's look at another example, this time, at a trait that did evolve after divergence. Cows and horses. They both have hooves, and yet there are clear structural differences between them. Each walks on essentially their finger tips, with a hard protective covering on each of the digits that bears the weight. However, in horses, the weight is born on a single digit, and in cows the weight is born on two digits. So it's unlikely that the common ancestor of cows and horses was hoofed. After all, let's say it was. Did it have one hoof or two? If it had two, then all horses (including animals like zebras, etc) must have evolved to lose one. And if it had one hoof, then all cows and related animals (including ox, bison, etc) must have evolved to gain one. So the more rational answer is that the common ancestor had not yet evolved hooves, and both the horse family and the cow family both evolved hooves, but because they could not interbreed and share the DNA which would allow them to pass on traits, they each had to evolve their own version of hooves. And that's why they have different types of hooves.

You may find this website interesting. It shows the tree of life, and you can follow it to see where two different species have a common ancestor. OneZoom Tree of Life Explorer

 

[Kylie]

And I realise now that the last two posts of mine were responding to posts that I had already responded to. Ah well.

 

[DialecticSkeptic]

And I realise now that the last two posts of mine were responding to posts that I had already responded to. Ah well.

I thought I had read that somewhere before.

 

[Mark Quayle]

@Mark Quayle let's move on. In statement 3, I spoke of how parents pass their genes on to their offspring. We've already covered this a fair bit, what with the different allele's for eye colour and such, so may I assume you have no reservations about that?

Anticipating that you will have no reservations, let's also cover Statement 4, where I said that different traits can influence how well the individual animal that has them survives. Do you have any reservations regarding that statement?

Only the reservations I already mentioned.

 

[Kylie]

Only the reservations I already mentioned.

Would you be so kind as to repeat them?

 

[Mark Quayle]

I think you misunderstood.

If the mother and father are Bb, then there are several different ways that the genes can be passed to the offspring.

1. The mother could pass on her B, and the father could pass on his B. In this case, the offspring will be BB and will have brown eyes.
2. The mother could pass on her B, and the father could pass on his b. In this case, the offspring will be Bb and will have brown eyes (since the dominant B allele from the mother overrides the recessive b allele from the father).
3. The mother could pass on her b, and the father could pass on his B. In this case, the offspring will be bB and will have brown eyes (since the dominant B allele from the father overrides the recessive b allele from the mother).
4. The mother could pass on her b, and the father could pass on his b. In this case, the offspring will be bb and will have blue eyes.

Which of these four different results will occur is random, since the allele that the mother passes on is random, as is the allele the father passes on. Each parent has two alleles for themselves (for example, I know I am either bb, or I am Bb with a gene that "cancels out" my B, since I have blue eyes). But I only passed one of them to my daughter.

I can't accept 'is random'. 'Appears random', perhaps. But I guess I get your point.

But I thought a Bb mother and Bb father, necessarily "pass on" both B and b. But only one or the other or both will prevail in the offspring. But at this point we are playing with words, I guess, "pass on"; "be"; etc. I'm still just a little foggy on how this works, but oh well.

 

[Mark Quayle]

No. We could each do a DNA test and find out how closely related we are. Chances are we are not closely related at all. But, if we were to go back far enough, we would be able to find a person who is in my family tree and your family tree as well. This person probably lived several hundred years ago, of course. But we could determine approximately how many generations ago we shared this common ancestor. We would not need to trace every single descendant of that common ancestor on both sides in order for us to know approximately when they existed.

When it comes to different species, we can also look at shared traits. For example, let's say feathers (I'm just coming up with an example off the top of my head here). We might look at a hummingbird and an eagle and say that they are two species that are not closely related (in other words, saying their common ancestor lived a long time ago). But we can be quite sure that whenever this common ancestor lived, it was after the line had evolved feathers. I mean, let's assume that the common ancestor lived BEFORE feathers evolved. Then we'd have to assume that the eagle line evolved feathers after the line diverged, and the hummingbird line evolved the exact same trait completely independently in the same time. When you look at the similarities between feathers of hummingbirds and eagles, the chances of feathers evolving twice and being what we find in nature are absolutely miniscule. it's far more reasonable to say that the ancestor evolved feathers BEFORE the two different lines diverged.

Let's look at another example, this time, at a trait that did evolve after divergence. Cows and horses. They both have hooves, and yet there are clear structural differences between them. Each walks on essentially their finger tips, with a hard protective covering on each of the digits that bears the weight. However, in horses, the weight is born on a single digit, and in cows the weight is born on two digits. So it's unlikely that the common ancestor of cows and horses was hoofed. After all, let's say it was. Did it have one hoof or two? If it had two, then all horses (including animals like zebras, etc) must have evolved to lose one. And if it had one hoof, then all cows and related animals (including ox, bison, etc) must have evolved to gain one. So the more rational answer is that the common ancestor had not yet evolved hooves, and both the horse family and the cow family both evolved hooves, but because they could not interbreed and share the DNA which would allow them to pass on traits, they each had to evolve their own version of hooves. And that's why they have different types of hooves.

You may find this website interesting. It shows the tree of life, and you can follow it to see where two different species have a common ancestor. OneZoom Tree of Life Explorer

Both of your examples assume a common ancestor.