If I were a dog breeding lineage (me, my children, their children, their children...) and selected dogs with short hair and small stature over the years while not selecting too fast and keeping the general population numbers high... I could end up with a small dog with very short hair, yes?
Then, if my lineage decided to change it's selection to dogs with long hair and large stature over the years, again while not selecting too fast and keeping the general population numbers high... I could end up with a large dog with long hair, yes?
Isn't this what Faith is saying is flatly impossible? That breeding a small dog (or pick whatever feature you want) "loses" the ability of being a large dog (or anything that is not-the-feature-in-question)?
Isn't this done by many breeders today? I thought there were many breeds of things (birds, fish) that were bred in one direction traditionally, but lately breeders have been reversing the trends to give a "shock factor" in their attempts to sell animals? Sort of an "Oh my! A traditionally short-haired dog with long hair! I must buy it, my friends will all be so impressed because they've never seen such a thing!!"
Doesn't such breeding tactics fly directly in the face of Faith's breeding examples for this "loss" she claims to exist?
Or, maybe I'm just not understanding any of the arguments here...
If, however, you HAVE lost the long hair trait in your breed, so that you now have homozygosity for short hair at all the gene loci that govern hair length, then you won't be able to get the long hair from your breed...
I'm pretty sure that if we have fully and completely lost the long hair trait in the breed it's quite possible for a random mutation to happen that can be selected for to get long hair again without having to introduce any other dogs into the breed. And if we stop selecting for short hair, and start selecting for long hair again... well, the rest is normal breeding to get long hair into the population again.
This 'new' long hair gene will probably be different from the 'original' long hair gene.
You're saying such a thing is impossible? What would prevent it?
Are you saying that random mutations are impossible? I think this is rather against the evidence.
Are you saying it's impossible for a random mutation in any short haired breed to grant the ability to have long hair? I'm pretty sure this has been done many, many times by many different breeders.
Are you saying it's impossible for a random mutation in a "short haired breed that came from a long haired breed but lost the original long haired gene" to grant the ability to have long hair? If so, how would the mutation know it can't do that? What would prevent it?
Random mutations don't "know" or "remember" the past history of the breed...
(I point to the cheetah which has never had a beneficial mutation occur in all its generations to allow for any further evolution.)
I'm not sure if this statement is absolutely true or not. But the idea that the cheetah has very little genetic variation is very true.
However, the cheetah does not have very little genetic variation because it's "evolved a lot." The cheetah has very little genetic variation because it went through some sort of population bottleneck. Like a Noah's Ark kind of thing.
I agree that population bottlenecks can end evolution. Although it doesn't really "end evolution" so much as it "ends the species because they cannot reproduce." And evolution certainly ends when things are dead.
Everything has been evolving for basically the same amount of time.
Cheetah's have been around as long as pretty much any other mammal. Some a little more, some a little less. But Cheetah's aren't some exceptional "older than most" species or anything like that.
If what you're saying is true... that evolution itself is the culprit... then all species would be in the same boat as the cheetah. But they're not.
Sure, the cheetah has evolutionary changes to it's heart, respiratory system, muscles and limbs in order to run fast. But a bear has evolutionary changes to it's heart, respiratory system, muscles and limbs in order to be big and strong.
The bear is just as evolved into it's niche as the cheetah is into theirs. But bears aren't in fear of extinction like cheetahs are.
This is because bears haven't experienced the population bottlenecks that cheetahs have. Evolution isn't killing off the cheetah, population bottlenecks are.
I'm saying that such specific mutations as described above are highly improbable.
So you don't think it's impossible, just improbable.
My guess is that it would in fact be impossible and that even if you got a slightly longer haired pup it would take many generations before it got long enough to be what you have in mind by simply multiplying the effect of that one gene. And I don't even know if that's possible. The odds are seriously against you.
But I was talking about my lineage doing the selecting. My lineage is very good at identifying long hairs vs. short hairs. They look at the hairs and the longer one wins.
And many generations of dogs aren't a problem either... we're already going many generations of humans (my lineage) so for dogs it shouldn't be an issue at all.
Seems like the odds are somewhat better than being "seriously against me."
But, that doesn't matter. As long as you accept that such random mutations can happen, I think you're being reasonable.
Please ponder what I've written about this above about the odds against getting a particular mutation in the right place to be passed on etc etc etc. It's all a matter of getting a particular DNA sequence that codes for a particular protein in the germ cell. Consider the odds.
I understand that this would be more rare for a specific gene in my specific breeding example. But now let's go back to the wild with this information.
Now we're not looking for any specific gene. In fact, in order for random mutations to increase the genetic variety... they don't have to be for any specific gene or any benefit or any negative thing at all. All they have to do is occur. As long as random mutations are occurring (especially neutral ones), and the population is still reproducing and growing... then the genetic variety is going to increase.
If random mutation do not occur and this increase in genetic information doesn't happen before the next speciation event... and the next, and the next and the next... then I agree with you. Eventually the species will die off, like the cheetah... because of population bottlenecks.
However, if the next speciation event doesn't happen for, say... hundreds of thousands of years... That's plenty of time to build the genetic variety as well as the population up so that the next possible loss in a speciation event doesn't hurt the population as a whole.
The point is only that it has fixed (homozygous) loci for all its characteristic traits, and although in the case of the cheetah that genetic condition was the result of a drastic Founder Effect, the same situation should certainly occur with a series of migrating populations over many generations of evolving new species or varieties etc
The drastic problem that happened to the cheetah was population bottlenecks. A lot of them were killed off. Perhaps by natural causes (earthquakes? famine? fire?), perhaps by people hunting them.
And, yes... the same thing happens to any species that goes through a population bottleneck. If the population bottleneck is too much... then the species has too much trouble reproducing due to inbreeding (lack of genetic variety)... and it goes extinct. If the population bottleneck is not too much... then the species recovers.
Bears have the same situation as cheetahs. They migrated populations over many generations of evolving new species or varieties just as the cheetah has. But the bear is not in trouble. The only difference is that cheetahs went through a population bottleneck. Bears did not.
It's not about niches and adaptation etc, it's about the degree of genetic diversity or genetic depletion. The bear in its niche probably has a great deal of genetic diversity left so it's not threatened by genetic depletion as is the cheetah.
The reason why bears have a great deal of genetic diversity is because there's lots of them. There's no population bottleneck. The large population allows time/chances for the random mutations to occur in bears over and over again in order to increase the genetic variety.
The reason why cheetahs have low genetic diversity is because there was only a few of them because of the population bottleneck. The small population is not allowing enough time/chances for the random mutations to occur in cheetahs so that the genetic variety cannot increase.
Different animals evolve at different rates.
Herd animals for instance should be able to maintain high genetic diversity in the wild for hundreds of years because they don't split into smaller populations very often.
The only thing that allows for high genetic diversity is whether or not something happens (like a population bottleneck) that would limit the amount of random mutation that can occur within the population.
The thing is, ANY time you get a new variety or species, meaning the formation of a population characterized by traits that differ from that of the parent population, you HAVE TO lose the genetic material for all the other traits that could occur in the population.
So you can have all the mutations you can dream up, they still have to be selected to bring about a new variety or species and selection reduces genetic diversity.
You do understand that not all traits have to be selected when a selection occurs, right? It's quite possible for dog breeders to select for hair length while not selecting nail growth or teeth hardness or ability-to-smell or length of legs or pupil size or...
Therefore, if you select for one thing, you don't have to lose "all" others... you only have to lose all others-that-have-to-do-with-that-one-specific-thing.
Therefore, if the mutations that occur are for all sorts of things... and the speciation event is only on one particular trait... then the vast majority of the mutations will remain and still count as an increase in genetic variety.
Here is an example with specifics:
Say we have a dog population with the following:
Hair - all the same Eye colour - all the same Nail length - all the same Ability to smell - all the same Length of legs - all the same
Now, 2000 years goes by and, due to random mutations we have a dog population like this:
Hair - some short, some long Eye colour - some dark, some light Nail length - some short, some long Ability to smell - some strong, some weak Length of legs - some short, some long
There are dogs of every combination of all these possible traits. The genetic variety has increased a lot.
Now, we have a speciation event - Only dogs with a strong ability to smell are selected, the rest are killed off 'cause they can't find food. So, we no longer have strong smellers and weak smellers, we have only strong smellers. We reduced the genetic variety.
But, we still have a dog population like this:
Hair - some short, some long Eye colour - some dark, some light Nail length - some short, some long Ability to smell - all the same (strong, not weak) Length of legs - some short, some long
Which still has a lot more variation than the original population 2000 years ago.
Wouldn't you agree? If not, which part of this scenario do you find impossible?
I've been following skeptically along because mutations have played a very minor role in the history of breeding, even if you extend the breeding period to 2000 years.
I'm not intending to use "breeding" as part of this example.
I'm only intending to use "dogs" and things like "hair length, strength-of-smell" because they are easily understood traits. I'm attempting to put a more practical-side (and perhaps easier-to-understand) spin on the conversation.
However, I am an amateur and am not familiar with how long things tend to actually take.
If we did have a dog species that was "all the same"... how long do you (approximately) think it would take to produce differences in the population like long hair/short hair and strong smellers/weak smellers for 5 different traits?
I just guessed at 2000 years (also, trying to keep the number low because I know Faith gets uncomfortable with higher numbers). Do you think such a thing would more reasonably be looking at something like 200,000 years? 2 million?
Depends on how large the founding population of your new species was. Most of the scattered mutations would stay behind in the parent population if the founding population was fairly small.
Exactly. It depends on if the population is large enough to recover from the population bottleneck or not. The cheetah seems to be having issues recovering. The bear does not.
We will see what happens to our dog population...
I don't find it impossible, just another case of increasing diversity to no evolutionary purpose as it were. In this case your mutations destroyed what was a homogeneous dog breed, sharing all the same traits, this destruction being what I keep saying has to happen if you introduce mutations into an established breed: you go from a breed to a mutt. You've reversed the effect of selection which had homogenized the breed. It's selection that does that, it's selection that turns a motley collection of traits into a recognizable breed.
Yes, I completely agree with the idea of going into a "mutt."
What I described with all the differences (hair length, smell strength...) becoming apparent after 2000 years is very validly described as turning the "once-all-the-same" dog population into more of a mutt population.
However, the size of the overall dog, the colour of it's hair, the shape of it's skull, the intelligence-range... any and all things not mentioned are assumed to still be the same.
Therefore, the "mutts" would all be recognizable as the same sort of dog... just some have long hair, others short. Some smell better, others weaker...
But yes, the variation that has gone through the population creates more of a "mutt" as opposed to a very-specific "breed" definition.
This does, however, still increase the genetic variety of "the population" of that dog.
Now, onto some more agreement with you:
So, after 2000 years, we have this:
Hair - some short, some long Eye colour - some dark, some light Nail length - some short, some long Ability to smell - same (all strong) Length of legs - some short, some long
After 200 years, we have another speciation event... leaving us with this:
Hair - some short, some long Eye colour - same (all dark) Nail length - some short, some long Ability to smell - same (all strong) Length of legs - some short, some long
We have "lost" the light coloured eyes.
After 200 more years, we have another speciation event... leaving us with this:
Hair - some short, some long Eye colour - same (all dark) Nail length - some short, some long Ability to smell - same (all strong) Length of legs - same (all long)
Here we have lost the short legs, and with the speciation events so close together, there isn't much time for the population to recover. Our dog population is becoming smaller and smaller and having to turn to more and more inbreeding. Just like the cheetah, reproduction for the dogs is becoming harder and harder.
After 200 more years, we have another speciation event... leaving us with this:
Hair - some short, some long Eye colour - same (all dark) Nail length - same (all short) Ability to smell - same (all strong) Length of legs - same (all long)
More trouble for the population...
After 200 more years, we have another speciation event... leaving us with this:
Hair - same (all short) Eye colour - same (all dark) Nail length - same (all short) Ability to smell - same (all strong) Length of legs - same (all long)
And now we have a dog population with extremely little genetic variation (much like the cheetah).
We have lost genetic variation over each speciation event, the population has gotten smaller and smaller. With a much smaller population, much more inbreeding occurs. With more inbreeding, reproduction gets more difficult (more likely for babies to die). Because the population is so small, and the speciation events happened to0 quickly... random mutations didn't have a chance to create any additional genetic variation.
This dog population is in danger of becoming extinct. Like the cheetah.
Is that an accurate representation of the ideas you've been trying to convey about how evolution *must* lead to a decrease in genetic variety?
I hope so, because that is what I was aiming for. If not, please let me know what you disagree with.
If you're talking about dogs left to their own devices, since they can all interbreed as far as I know, you don't need mutations at all, within a very few generations, give it a hundred if you want to lose all the characteristics of all the breeds, you'd have a mutt population with a mixture of different traits from all the breeds.
We are talking about dogs left to their own devices. And yes, they can all interbreed since they began "all the same" (apart from half being male and half female... otherwise they would all die very quickly.) And, actually, we are only talking about mutations adding to the genetic variety... since they started out "all the same."
They started out all the same, and then the population had some differences in it (long/short hair, strong/weak smelling ability...). All coming about through random mutations changing the genes. No selection. No environment pressures. Just a population living and reproducing and getting random mutations that eventually result in a few differences within the population.
OK sorry, I wasn't getting this clearly at all. ALl that came from mutations you are saying. but it can't happen that way. Mutations are going to occur just here and there in individuals in a population, and without selection you aren't going to get changes in the population at large.
I think this is the crux of your issue with random mutations increasing genetic variation.
Here's a new example:
We have a population of wolves. They are all the same. They do not breed with any other wolves at all. They only breed within their own population.
Here are some traits:
Length of hair - Same - all short Length of nails - Same - all short Colour of eyes - Same - all grey Colour of coat (hair) - Same - all black/white/grey Length of tail - Same - all short Width of paws - Same - all small Sharpness of teeth - Same - all sharp Angle of ears - Same - all sharp Broadness of chest - Same - all small Strength of heart - Same - all strong Strength of legs - Same - all short Ability to smell - Same - all strong (All other traits not listed... of which there would be thousands... are all the same).
After 500 years, we now have a population that looks something like this due to random mutation:
Length of hair - Same Length of nails - Same Colour of eyes - Different, some are blue, some are grey Colour of coat (hair) - Same Length of tail - Same Width of paws - Same Sharpness of teeth - Same Angle of ears - Same Broadness of chest - Same Strength of heart - Same Strength of legs - Same Ability to smell - Same
This would occur due to a random mutation that caused some eyes to be blue. As well, no wolves cared if the eyes were blue or grey so the ones that had blue eyes still reproduced and the trait spread throughout the population. The blue eyes simply were not selected out, and they grew to be a larger and larger part of the population. No speciation event. No selection. There's just wolves now with blue eyes in the population due to random mutation.
Are you saying such a thing is strictly impossible? If so, why? What would prevent it?