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Author Topic:   A test for claimed knowledge of how macroevolution occurs
Percy
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Posts: 18584
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.0


Message 691 of 785 (856967)
07-04-2019 12:28 PM
Reply to: Message 670 by Faith
07-03-2019 9:35 PM


Re: Creationist mindset
I really wish you wouldn't make yourself the topic of discussion, but if you insist on making false claims about yourself then others will be forced to correct you.

How can I be expected to take seriously the constant refrain about how I don't understand this, that or the other when nobody ever even gives an example of what that means?

It is the rare message from you that doesn't contain multiple factual errors, and people have corrected you many, many times. You have no excuse for understanding biology and geology as poorly today as when you joined nearly 18 years ago.

You don't, JonF doesn't, but it's said all the time.

Everyone has provided a multitude of examples over many years of what you don't understand, often providing the factual basis.

If an example IS ever given then I can answer it, because it never really amounts to much and doesn't threaten anything I've been arguing though that's of course what the accusation implies. Mostly it amounts to saying my argument is wrong because it contradicts the establishment argument, really no more than that. So I just shrug off these endless empty accusations.

You are as delusional about the quality of your views as you are about the degree of your scientific understanding.

--Percy


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 Message 670 by Faith, posted 07-03-2019 9:35 PM Faith has not yet responded

    
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Message 692 of 785 (856970)
07-04-2019 12:38 PM


Please Don't Discuss Flood Issues Here
I'm a participant in this thread and so shouldn't be moderating, but it doesn't seem unreasonable to briefly slip into my moderator role to ask that people move discussion of flood issues to the Geology and the Great Flood forum. There are a number of appropriate threads there, or new ones may be proposed.

--Percy
EvC Forum Director

    
RAZD
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Posts: 19977
From: the other end of the sidewalk
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Message 693 of 785 (856982)
07-04-2019 1:36 PM
Reply to: Message 630 by Faith
07-01-2019 5:07 PM


Faith's "homogenous" population
and if you ignore selection, mutation and ecological forces (as you have claimed), in what you call a "homogeneous" population, then those combinations should exist in the parent population.

As I say above, they could, but it's not necessary for them to have been expressed there beyond the occasional occurrence which is hardly noticeable in a large population of motley traits with a general homogeneous appearance. It's all a matter of gene frequencies.

Is this what you mean by a "homogeneous" population, that they have a "general homogeneous appearance" ... (with some variation presumably in size)?

Would "motley traits" mean the various traits (color, legs, horns, etc) that go to make up each individual?

Curious.

... It's all a matter of gene frequencies.

I assume they were all in the parent population but for some reason more potential than expressed. ...

So there is also the case of a very large herd population with high genetic diversity that can be the source of strongly different traits in daughter populations. ...

A large herd with "high genetic diversity" would have many variations in phenotypes with "strongly different traits" ... as shown by the analysis with Mendalian inheritance in Message 587.

... So I now have the idea that traits don't necessarily manifest in some obvious way at first, just enough to be selected in breeding, or even in nature, but not enough to show up in a herd unless you go through it individual by individual. It takes the new gene frequencies to begin to emphasize such traits and bring them to observable expression in the new population. You all rely on mutations to explain all this although I don't think that's even possible, but in any case my model has new characteristics emerging even in dramatic ways in daughter populations that didn't get expressed in the parent population, or not to any noticeable degree.

But you ignore selection, mutation and ecological forces, in the formation/development of all phenotypes, and you are positing a "homogeneous" parent population, so you have no mechanism to make traits that don't "necessarily manifest in some obvious way at first, just enough to be selected in breeding, or even in nature, but not enough to show up in a herd unless you go through it individual by individual." Rather they should all be seen in the parent population.

And how do you know that the changes in the sub-populations are not due to mutations?

Curious again.

Enjoy

Edited by RAZD, : .


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Percy
Member
Posts: 18584
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.0


(1)
Message 694 of 785 (856986)
07-04-2019 1:41 PM
Reply to: Message 568 by Faith
06-29-2019 8:47 PM


Re: Lab experiment
Faith writes:

Percy writes:

Faith writes:

Continue until the latest daughter populations run out of genetic variability.

Unless the experimenters place the mice in environments that subject them to substantial selection pressures, or if the mice populations are small, reductions in genetic diversity would be unexpected.

The more individuals the better. But do your own lab experiment, you obviously haven't a clue to mine. Predict all you want based on your erroneous ToE beliefs, I intend to prove that you'll get genetic decrease with this method.

No selection pressures needed, and of course I want to start with as large a population as can be managed in a laboratory, and after its numbers increase quite a bit just letting them breed for a while, then I want to remove a smallish number of individuals to start the experiment proper.

I know what I'm doing although it's very clear you don't.

You said, "Continue until the latest daughter populations run out of genetic variability," and that's what I was responding to. What are you imagining is going to cause daughter populations to run out of genetic variability? Here's your experiment boiled down to bullet points and filling in some ambiguities that you can correct if I have it wrong:

  1. Start with a population of 100 mice. Measure the genetic diversity.
  2. Let the population grow to 400, then divide it into four populations of 100 mice. Each population will have roughly the same genetic diversity as the original population of 100 mice. The four habitats should be identical so that selection pressures are the same. Measure the genetic diversity of each population.
  3. Repeat step 2 until the daughter populations "run out of genetic variability" (your words). Keep in mind that you can't repeat step 2 too many times unless you have a very large laboratory and hefty financing. After 1 generation you have 4 100-mouse populations. After 2 generations you have 16 100-mouse populations. After 3 generations you have 64 100-mouse populations. After 4 generations you have 256 100-mouse populations. After 5 generations you have 1024 100-mouse populations. You get the idea.

Please correct the above until I have it right, then answer the question of what is going to cause the daughter populations to "run out of genetic variability."

You're probably thinking that at each division into four daughter populations that some alleles wouldn't make it, and you would be correct for rare alleles in the original population. It would not cause the daughter populations to "run out of genetic variability."

Certainly, we aim for the greatest genetic diversity we can get, that's all, the best we can do given the limitations of the lab setting. We might have to wait through some number of breeding generations to get a homogeneous appearance before the experiment proper can even begin. But I know you haven't a clue what I'm talking about so I guess I can't expect you to raise money to finance my project.

The term "homogeneous appearance" is ambiguous. It sounds like you mean something like genetically uniform, which would be synonymous with a reduction in genetic diversity, but this is unlikely to occur even after many generations of breeding unless some kind of strong selection pressure is applied, like selecting for specific coat color, head shape, tail length, ear size and shape, etc. In the absence of strong selection pressures by the breeder the mouse population will remain about as genetically diverse as when they started.

--Percy


This message is a reply to:
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Percy
Member
Posts: 18584
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.0


Message 695 of 785 (857003)
07-04-2019 4:15 PM
Reply to: Message 610 by Faith
07-01-2019 3:40 PM


Re: The genetic loss idée fixe vs reality
Faith writes:

It's the same processes, the same mechanisms, the same genetics that produce both breeds and species.

Even though you use the word "breeds," I don't think you're talking about breeding but about races and subspecies.
Yes, the same processes govern the creation of races, subspecies and species, but species implies a reproductive barrier with other species.

Most species in the wild are probably able to breed with other populations but just don't.

This is ambiguous. If you're saying that species in the wild can breed with other populations of the same species, this is undoubtedly true. If you're saying that species in the wild can breed with other populations of related species, this can be true, though the offspring can experience abnormalities or infertility depending upon the degree of relatedness. If you're saying that species in the wild can breed with populations of many other species in the wild then this is undoubtedly false.

Explaining in a bit more detail, it is not uncommon for species to be able to breed with other closely related species. Because they're closely related, tigers can interbreed with lions, leopards and panthers, zebras with horses and donkeys, camels with llamas, etc. But species cannot breed with other unrelated species, not in the wild and not in the lab. For instance, while tigers can breed with lions, leopards and panthers, they cannot breed with cheetahs, bobcats, housecats, zebras, gazelles, rabbits, gophers, hippopotamuses, rhinoceroses, lemmings, turtles, frogs, birds and fish.

A physical inability to interbreed is an artificial dividing line.

I understand what you're trying to say, so let me say it another way: In the wild some species that are genetically able to interbreed simply do not, or at least only rarely. The reason could be physical, behavioral, geographical, or some combination.

I had a reason for posting the pigeons. I am interested in the question of how the same trait is increased by being selected over generations. I assume it is the same gene or genes that underlie the trait.

Or course it's a gene or genes controlling the trait. When the breeder selects mating pairs based upon a certain trait, on a genetic level he's selecting or deselecting (both are possible) alleles of that gene(s) related to that trait. In other word, he's causing allele frequencies that favor that trait.

The exaggerated size of the lizards' head and jaw on Pod Mrcaru suggests the same kind of genetic situation.

If you mean allele frequencies favored these changes then yes, you are correct. But as Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource tells us, "Genetic mitochondrial DNA analyses indicate that the lizards currently on Pod Mrčaru are indeed P. sicula and are genetically indistinguishable from lizards from the source population." That is, the genetic changes were very minor.

I really don't care about being precise about the meaning of "homogeneity."

Nobody's insisting on razor sharp precision. We just want to know what in the world you mean. Your insistence on words and phrases that are vague and ambiguous is what convinces people that you don't know what you're talking about and, as you just said yourself, that you don't really care. If that's really true then you're probably the only one here who doesn't care whether they're right or wrong or understand the discussion or are making themselves understood.

It is apparent that locked away in your imagination is that a population becomes more "homogeneous" over time, that the alleles become distributed more and more evenly in the population, and that the individuals become more and more similar. There is absolutely no evidence of this in population genetics.

I was interested in THAT question for a similar reason: what is it genetically that allows for the overall appearance of homogeneity when there is high genetic diversity in the population?

The "appearance of homogeneity" is just something else from your imagination. You're analogous to the cop on the beat who says about blacks that they all look alike to him. You look at a population of pigeons and think how alike they all are, but they're really not alike at all. Look at how different all these pigeons are:

We have a bird feeder, and even just glancing at them casually you can see the many differences between individual nuthatches, goldfinches, woodpeckers, wood doves and so forth.

In the scenario I lay out for how a new population becomes a species...

But who could know what you mean by this because you've made up your own definition of species where a new species is actually still the same species, they just choose not to interbreed. But the real world definition of species is a population that can interbreed. If two populations are still capable of interbreeding (without abnormalities or infertility) then they are, by definition, the same species. As populations become more and more distant genetically then interbreeding gradually becomes less and less likely to produce viable offspring.

At what point does one declare two populations to be different species? When viable offspring are produced less than 80% of the time? 50% of the time? 10% of the time? This isn't a question that science has attempted to answer yet, at least not that I'm aware of. Of course, it would be a judgement call anyway.

I see it through stages from some set of individuals that leave the parent population looking just like all the others in that population -- another case of appearance of homogeneity with unknown levels of genetic diversity, and again no I'm not interested in getting precise about it, it's not relevant to anything I'm saying.

Again, we don't need razor sharp precision, but we do need to know how you're defining your terms. You should stop using the term "homogeneous" because there is no agreement on what you mean by it. I think what you're trying to say is that when a subpopulation first splits off from the main population that it has the same level of genetic diversity as the parent population. This is true as a first approximation, but in general a subpopulation can't help but have at least slightly less genetic diversity than the parent population. Or if a population splits roughly in half then each half will likely have slightly less genetic diversity then the original population.

  • That's stage one, founding population that looks like parent population. This could be the all-one-color of a herd animal or it could be a raccoon population with distinctive markings.

You have a mistaken idea of the amount of variation in a parent population. Look at how different all these wildebeest are with regard to size, build, coat, stripes, horns, facial coloration, eyes, nose, etc.:

I once drove through a bison herd in South Dakota. The difference in appearance between all the bison was striking, not to mention the difference in temperament. Some would challenge the van, blocking the road and facing us down. Others quickly scampered off to the side as we got closer. Some got out of the way but took their own sweet time.

Since this new population will have a new set of gene frequencies I'm expecting them to produce a new look in the new population over some number of generations of breeding only within the population.

But you just said the "founding population...looks like the parent population." If it has a new set of allele frequencies, how could it also look just like the parent population? Can you clear this up?

  • Stage two is where breeding within the new population begins. The offspring may or may not have observably different characteristics from the parents, but by

Unless selection pressures are different they'll very closely resemble the parent population.

  • Stage three new characteristics should start to emerge from the new combinations of alleles, including a new pattern of markings on an animal like a raccoon.
  • And reproductive stages beyond that should bring out even more new characteristics, again all from recombination of the new gene frequencies.

Again, unless selection pressures are different they'll very closely resemble the parent population, and especially if there's still gene flow with the parent population.

  • The end result should be that the whole population will have blended together to form a new appearance of homogeneity that is distinct from the original population and from all other populations of the same species. A completely new pattern of markings would probably identify the new raccoon population.

Again, that individuals of a population become more and more similar across the generations is just something from your imagination. There's no evidence for it. Without strong selection pressures genetic diversity would be maintained.

Yes I'm imagining how this would play out in my model. But the lab experiment I've described is for the purpose of proving it.

Given the huge number of biology experiments that have been conducted and all the research into population genetics, what you describe could not have escaped notice if it were what really happens.

I expect my opponents to describe their own completely different scenario with the mutations and the ecological selection pressure and so on, and even be adamant that it's the correct scenario based on the ToE, but I strongly object to telling me I'm wrong because I don't share that scenario. No, if that's going to be the attitude, sorry, YOU are wrong.

It isn't necessary to run your experiment to know that you are wrong. Nothing you said aligns with what we already know to be true about the genetic diversity of populations.

--Percy


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Sarah Bellum
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Posts: 224
Joined: 05-04-2019
Member Rating: 2.4


Message 696 of 785 (857018)
07-04-2019 10:36 PM
Reply to: Message 674 by Faith
07-04-2019 12:02 AM


Re: Flood stuff
The idea of the Flood laying down geological strata was debunked long ago. To take just one example, fossils are sorted by time period: earlier organisms at lower levels. A flood would have jumbled everything up, humans with trilobites and dinosaurs with dogs, etc.

The idea of the Grand Canyon being carved by a massive flood was debunked long ago: it is, for instance a deep, meandering riverbed, not a wide, shallow, direct path.

As for the corals, how could they have survived being buried under all that sediment? Since they didn't survive, we wouldn't see any reefs nowadays. Even if Noah had brought along some coral larvae and released them after the flood, how could they have grown to the depth and worldwide extent that we see today?


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Replies to this message:
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Faith
Member
Posts: 32133
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 697 of 785 (857022)
07-04-2019 11:21 PM
Reply to: Message 696 by Sarah Bellum
07-04-2019 10:36 PM


Re: Flood stuff
Right, well they weren't all jumbled up in the Flood, somehow they got sorted by the Flood. Ocean water is layered by the way, and layers are easily formed by water. And if they were going to be jumbled up it should have been in the jumbled up mixtures of dirt that normally occur on the earth instead of in those supposed burial grounds of oh-so neat horizontal sediments of the time periods over those supposed millions of years. If animals just lye down and die, it isn't in such perfect graveyards. And so many of them, one for each "time period" that came along to bury them. Besides which, fossilization is a rare occurrence but the Flood would have suppled ideal conditions for the fossilization of bazillions of animals. WHICH, by the way, are evidence of the purpose of all that death in the Flood as described in the Bible.

A massive amount of rushing water cascading down through widening cracks and over the sides would certainly do a fine job of carving the canyon. And again what's ridiculous there is the idea that an ordinary river carved out that enormous space.

Lots of fragile things were preserved in the sediments which precipitated down over them.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


This message is a reply to:
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Replies to this message:
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AZPaul3
Member
Posts: 4258
From: Phoenix
Joined: 11-06-2006
Member Rating: 3.7


(1)
Message 698 of 785 (857026)
07-05-2019 12:06 AM
Reply to: Message 696 by Sarah Bellum
07-04-2019 10:36 PM


Re: Flood stuff
Can’t you believe in majik from the old girl’s heart
How the majik can tell you anything that you want
Cuz it’s majik and the strata is bolder
Got all laid down at once with the fossils in order

You know the fluddy is majik that’ll save your soul
We all singin' and dancin' to god’s own rock and roll
Yes, it’s majik (yah ya know it's majik)
Gotta believe in majik (yah ya know it's majik)


Eschew obfuscation. Habituate elucidation.

This message is a reply to:
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Replies to this message:
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Sarah Bellum
Member
Posts: 224
Joined: 05-04-2019
Member Rating: 2.4


Message 699 of 785 (857031)
07-05-2019 12:35 AM
Reply to: Message 697 by Faith
07-04-2019 11:21 PM


Re: Flood stuff
You say, "somehow they got sorted by the Flood." But that's not what happens in a flood, is it? On the other hand, accretion over millennia does lay down layers "sorted" in historical order. That's not even mentioning the lava flows that appear in between sedimentary layers. Hard for a flood to lay down lava.

And no, rushing flood waters would not have worn out a riverbed like that. "Upstream of the Grand Canyon, the San Juan River (around Gooseneck State Park, southeast Utah) has some of the most extreme meandering imaginable. The canyon is 1,000 feet high, with the river flowing five miles while progressing one mile as the crow flies (American Southwest n.d.). There is no way a single massive flood could carve this." - http://talkorigins.org/indexcc/CH/CH581.html


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 Message 697 by Faith, posted 07-04-2019 11:21 PM Faith has responded

Replies to this message:
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Sarah Bellum
Member
Posts: 224
Joined: 05-04-2019
Member Rating: 2.4


(3)
Message 700 of 785 (857032)
07-05-2019 12:36 AM
Reply to: Message 698 by AZPaul3
07-05-2019 12:06 AM


Re: Flood stuff
I'm a black magic woman, but I don't believe in magic.
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Tangle
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Posts: 6950
From: UK
Joined: 10-07-2011
Member Rating: 5.1


(2)
Message 701 of 785 (857036)
07-05-2019 2:58 AM
Reply to: Message 681 by Faith
07-04-2019 6:58 AM


Re: Creationist mindset
Faith writes:

All it really tells me is that different creationists choose different problems according to what they think they can work with best. Same as I do.

That's amusing. Creationists have been doing that for thousands of years and getting nowhere. Science has been at it for a couple of hundred and has a consensus.

It's game over for YECs and has been for centuries. Your all individuals hiding in caves shouting.


Je suis Charlie. Je suis Ahmed. Je suis Juif. Je suis Parisien. I am Mancunian. I am Brum. I am London.I am Finland. Soy Barcelona

"Life, don't talk to me about life" - Marvin the Paranoid Android

"Science adjusts it's views based on what's observed.
Faith is the denial of observation so that Belief can be preserved."
- Tim Minchin, in his beat poem, Storm.


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Faith
Member
Posts: 32133
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 702 of 785 (857050)
07-05-2019 7:35 AM
Reply to: Message 699 by Sarah Bellum
07-05-2019 12:35 AM


Re: Flood stuff
What on earth do you mean by rushing waters "wearing out" a river? None of the rivers that are now in the area of the Grand Canyon were there at the point when the Flood started draining.

ABE: Sorry, I misread you, answered what you actually said in Message 704 /abe

"That's not what happens in a flood" is the usual utterly ridiculous attempt to turn this worldwide catastrophe into any ordinary flood. The only part of it that was like a usual flood would have been in the beginning and then it would have been like a million floods all over the planet causing mudslides and waterfalls. In THE Flood besides all that happening, the oceans rose up over the land and yes water does create layers.

And your assertion that time periods would do that is just some kind of wishful inability to think about it. That is about the most absurd thing claimed about the scenario of the fossil record, yet normally intelligent people just won't let themselves think about it.

There are very few places where lava intrudes into the layers and it's very clear that most of it happened after the sedimentary layers were already laid down.

So you're getting your stuff from Talk Origins. I can go there myself you know. How about being original? Obviously you haven't given a moment's thought to anything I actually said, about how rivers would have formed AFTER the Flood had drained, and meanders as well, on the flat surfaces such as the Kaibab plateau, that had been scoured off by the retreating Flood. This scenario works very well and it's all my own, I don't go to creationist sites to get my stuff..

Look, we're on the wrong thread for discussing the Flood and I'm not going to continue this with you. I've discussed it at great length on many threads here and your stuff is just the usual collection of crap that gets thrown at creationists all the time. Since you haven't followed my previous presentations of my argument you don't have a clue about any of it and I'm not up to it right now.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.

Edited by Faith, : No reason given.


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Pressie
Member
Posts: 2074
From: Pretoria, SA
Joined: 06-18-2010
Member Rating: 2.7


Message 703 of 785 (857051)
07-05-2019 7:58 AM
Reply to: Message 702 by Faith
07-05-2019 7:35 AM


Re: Flood stuff
Faith writes:

What on earth do you mean by rushing waters "wearing out" a river?

That's not exactly what was written. Why do you write so many untruths?

Edited by Pressie, : No reason given.


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Faith
Member
Posts: 32133
From: Nevada, USA
Joined: 10-06-2001
Member Rating: 1.1


Message 704 of 785 (857054)
07-05-2019 8:20 AM
Reply to: Message 703 by Pressie
07-05-2019 7:58 AM


Re: Flood stuff
Oh I misread it, thanks. WORN OUT A RIVERBED.

OK, the answer to that is the river wore out the riverbed over the last 4300 years. And it's absurd to think I was saying the rushing water had anything at all to do with the current riverbed.


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RAZD
Member
Posts: 19977
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.9


Message 705 of 785 (857055)
07-05-2019 8:28 AM
Reply to: Message 637 by Faith
07-02-2019 4:43 AM


Species and Speciation Events
I'm OK with varieties or subspecies but as I said one often hears such populations referred to as species.

The biological test for species is whether or not they interbreed with other populations. That's because of the definition of species used in biology.

quote:
Defining speciation

Speciation is a lineage-splitting event that produces two or more separate species. Imagine that you are looking at a tip of the tree of life that constitutes a species of fruit fly. Move down the phylogeny to where your fruit fly twig is connected to the rest of the tree. That branching point, and every other branching point on the tree, is a speciation event. At that point genetic changes resulted in two separate fruit fly lineages, where previously there had just been one lineage. But why and how did it happen?

The branching points on this partial Drosophila phylogeny represent long past speciation events.


Look familiar?

There are some difficulties, however:

quote:
Defining a species

A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions.

For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator.

That definition of a species might seem cut and dried, but it is not — in nature, there are lots of places where it is difficult to apply this definition. For example, many bacteria reproduce mainly asexually. The bacterium shown at right is reproducing asexually, by binary fission. The definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually.

Also, many plants, and some animals, form hybrids in nature. Hooded crows and carrion crows look different, and largely mate within their own groups — but in some areas, they hybridize. Should they be considered the same species or separate species?

If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species? There are lots of other places where the boundary of a species is blurred. It's not so surprising that these blurry places exist — after all, the idea of a species is something that we humans invented for our own convenience!


Classification is for our use in discussions, and they are subject to change when information provides new insights.

quote:
Carrion Crow: Distribution and genetic relationship to hooded crows

The carrion crow (Corvus corone) and hooded crow (Corvus cornix, including its slightly larger allied form or race C. c. orientalis) are two very closely related species[7] whose geographic distributions across Europe are illustrated in the accompanying diagram. It is believed that this distribution might have resulted from the glaciation cycles during the Pleistocene, which caused the parent population to split into isolates which subsequently re-expanded their ranges when the climate warmed causing secondary contact.[8][9]

A map of Europe indicating the distribution of the carrion and hooded
crows on either side of a contact zone (white line) separating the two species

Poelstra and coworkers sequenced almost the entire genomes of both species in populations at varying distances from the contact zone to find that the two species were genetically identical, both in their DNA and in its expression (in the form of mRNA), except for the lack of expression of a small portion (<0.28%) of the genome (situated on avian chromosome 18) in the hooded crow, which imparts the lighter plumage colouration on its torso.[8] Thus the two species can viably hybridize, and occasionally do so at the contact zone, but the all-black carrion crows on the one side of the contact zone mate almost exclusively with other all-black carrion crows, while the same occurs among the hooded crows on the other side of the contact zone.

It is therefore clear that it is only the outward appearance of the two species that inhibits hybridization.[8][9] The authors attribute this to assortative mating (rather than to ecological selection), the advantage of which is not clear, and it would lead to the rapid appearance of streams of new lineages, and possibly even species, through mutual attraction between mutants. Unnikrishnan and Akhila propose, instead, that koinophilia is a more parsimonious explanation for the resistance to hybridization across the contact zone, despite the absence of physiological, anatomical or genetic barriers to such hybridization.[8]


Also see Two species of crow evolving ... on this possible crow speciation in process, apparently due to coloration:

quote:
"Only two major effect genes which together encode the feather colour differ sharply on either side of the hybrid zone - the gray alleles are not found to the west of the zone and the black allele is absent in the eastern region," Wolf said.

Breeding populations apparently separated by sexual/mate selection.

quote:
Koinophilia is an evolutionary hypothesis proposing that during sexual selection, animals preferentially seek mates with a minimum of unusual or mutant features, including functionality, appearance and behavior.[1][2][3][4][5][6] Koinophilia intends to explain the clustering of sexual organisms into species and other issues described by Darwin's Dilemma.[3][4][5] The term derives from the Greek, koinos, "common", "that which is shared", and philia, "fondness".

Natural selection causes beneficial inherited features to become more common at the expense of their disadvantageous counterparts. The koinophilia hypothesis proposes that a sexually-reproducing animal would therefore be expected to avoid individuals with rare or unusual features, and to prefer to mate with individuals displaying a predominance of common or average features. ...


This Koinophilia is similar to what I proposed for sexual selection in Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution and my discussion on the causes of stasis in breeding populations living in stable ecological habitats.

This Crow mate selection is similar to the overlap of the end of ring species like the Greenish Warbler, another place where the definition of species is problematic.

For the record, the crows are listed in List of Corvus species as different species, likely because they were classified before genetic information was available, based on appearance and behavior.

Note that you should be delighted that the hooded crow seems to be a product of isolation and gene loss promoting a phenotype that was not apparent in the parent population. The loss is a mutation, of course.

Enjoy


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