Starting today August 7th, 2024, in order to post in the Married Couples, Courting Couples, or Singles forums, you will not be allowed to post if you have your Marital status designated as private. Announcements will be made in the respective forums as well but please note that if yours is currently listed as Private, you will need to submit a ticket in the Support Area to have yours changed.
Why can't you just accept that you are wrong?You must be a well paid researcher! Your examples all show the eardrum in front of the reflective surface.
The hearing horn being the least obvious. But in fact, I was wrong. The eardrums are not hidden behind the
owls feathers or below the curve of the reflective surface, as I stated knew they couldn't be.
And the owls face is not concave either as was originally argued.
This thread is getting mighty long..
Is the OP sill open for questions?
I have heard of a type of owl, though I don't know the name of it, which has a face that is shaped like a dish, as in a statellite dish. It also has left and right ear holes that are vertically out-of-line with respect to each other. This owl has amazing hearing and can tell accurately where sounds are coming from, including vertical components.
How could such a bird evolve in such a way. How did his/her alleged ancestors evolve a dish face, especially, the beginning stages, i.e., the owl's face slightly becoming concave. Wouldn't an ever-so-slightly concave face have no real advantage over a non-concave face. Do you get what I mean?
How does the DNA know to keep on mutating on the same direction? How does the DNA mutate so that the owl's face becomes concave and then more concave without going slightly less concave (or going slightly convex)?
I suppose that might still be due to whether the mutation exhibits an advantage or disadvantage.
What are the chances of the same type of advantageous mutation occurring time and time again? The DNA has no choice which DNA to mutate and has no say as to whether the mutation is going to be advantageous one or not. I also wonder how many advantageous mutations are needed in such a case. It seems like a very unlikely scenario to me.
Why can't you just accept that you are wrong?
Hi, I'm back, quoting my own question.
Firstly, I understand that this owl has a face that is shaped like a satellite dish, but doesn't operate exactly like a satellite dish. But I do understand that this owl has outstanding hearing capability due to the shape of its concave face and it's asymmetrically positioned ears.
I think I understand, in theory, how natural selection could work.
Exactly. The mutations cause change in both ways - but only one way causes an advantage. Mutation is random, but natural selection is not, and it's natural selection that picks which mutations get passed on and which don't.I assume we are talking about mutations that occur in the owl's DNA.
How does the DNA know to keep on mutating on the same direction? How does the DNA mutate so that the owl's face becomes concave and then more concave without going slightly less concave (or going slightly convex)?
I suppose that might still be due to whether the mutation exhibits an advantage or disadvantage.
It's actually not. Mutations occur all the time, causing small variations in the average individual. It may seem counter-intuitive (and it is!), but the universe doesn't care about our intuitionWhat are the chances of the same type of advantageous mutation occurring time and time again? The DNA has no choice which DNA to mutate and has no say as to whether the mutation is going to be advantageous one or not. I also wonder how many advantageous mutations are needed in such a case. It seems like a very unlikely scenario to me.
True. How often the same type of change is going to arise depends on the genetic underpinnings of a trait. For example, something like height is probably influenced by many, many genes. Mutations in any of them could potentially lead to the person being taller, so new mutations producing taller people would be relatively common. On the other hand, if a trait is determined by a few genes or even a single gene, advantageous mutations may be rarer, and it may be more difficult to collect more than one of them.What are the chances of the same type of advantageous mutation occurring time and time again? The DNA has no choice which DNA to mutate and has no say as to whether the mutation is going to be advantageous one or not.
This is a surprisingly difficult question to answer. Individual mutations can have very small or very large effects, and this is a bit unrelated to the type or size of the mutation. Some "small" mutations have large effects on the organism. For example, this terrible disease is often caused by the replacement of a single DNA base. So is the sickle-cell haemoglobin that can confer malaria resistance if you only inherit it from one parent and give you sickle cell disease if you inherit it from both. Flies with their antennae transformed into legs or their legs transformed into antennae can be made by changing the activity of just one gene. And then you can delete millions of base pairs from an animal's DNA and not see any obvious effect.I also wonder how many advantageous mutations are needed in such a case. It seems like a very unlikely scenario to me.
What are the chances of the same type of advantageous mutation occurring time and time again?
It seems like a very unlikely scenario to me.
I thought this was a really good question that needed more attention.
The answer is . . . extremely low. That is why any single advantageous mutation is much more likely the result of a single event that spreads through a population over several generations than several independent events.
Then there is the reproductive process that reduces the likelihood of expression by 50% in general. So vast numbers of the same mutation is required in order to show up in one offspring. Where it is again diluted by 50%
So DNA expression is not like language. Language sets can pick up a new word and promote it by a thousand fold or a million fold in one generation. Actually in about 2 hours most of the worlds population could be exposed to a new word. Intercourse is a slower process. At my house anyway.
Which still points to it not happening. Most mutations are fixed by repair genes.
So vast numbers of the same mutation is required in order to show up in one offspring.
So DNA expression is not like language. Language sets can pick up a new word and promote it by a thousand fold or a million fold in one generation. Actually in about 2 hours most of the worlds population could be exposed to a new word. Intercourse is a slower process. At my house anyway.
BUT DEY'RE STILL DAAAAAGSIf you still don't believe that genetics and mutation can produce enough variation for evolution to work on, just take a look at what happened to dogs in 10 thousand years:
Only in the most contrived way possible. Such a scenario would only occur if the system were set up so that, at a specific point in time (say, the early 21[sup]st[/sup] century), dogs looked like they evolved from a common ancetsor. It wouldn't happen as a by-product of some other function.Thanks everyone for your interesting replies. I feel as though I have learnt something.
I have a very different question this time. It is related to DNA but a somewhat different concept to natural selection, as far as I can understand it. Namely, taking the example of the dogs in that chart above. I think it would be fair to say that all dogs have one common first ancestor of dog. Suppose the first ancestor of dog was created with all the DNA of the dogs included in that chart. However the first generation puppies, though having approx. the same amount of variety of DNA, would have no choice but to mate amongst themselves, which in itself would pose no problems with birth defects because they still have a large variety of DNA. However, after a number of generations, these dogs divided up into different families, and each family moved further and further apart from each other. After more and more generations, these families became different 'breeds' of dogs. However, now, none of these breeds have anywhere near the amount of variety of DNA that the first ancestral dog had.
Now for my question, if someone were to study the DNA of these various modern dog breeds, would their DNA give the illusion of being evolved via natural selection? Richard Dawkins sometimes mentions the phrase "illusion of design", could an illusion of evolution be possible?
Weren't you just criticizing people for twisting the facts to make points in another thread? This is completely wrong, learn some genetics before you post stuff like this.
We know, as a matter of fact, from sequencing entire human genomes, that every human being has on average 50 to 100 mutations on its genome.
In other words, every child is 50 to 100 mutations away from the combination of their parents genes. And no, "vast numbers of the same mutation" are not required for it to show up. The only requirement is that the said mutation happens in an egg or sperm.
Now, if you multiply that 50 to 100 by the number of humans in this planet, times the number of generations that you want to go back you will get a grasp of how much genetic variation there is in humans.
If you still don't believe that genetics and mutation can produce enough variation for evolution to work on, just take a look at what happened to dogs in 10 thousand years.
I meant the ancestral dog was created having the entire gene pool for the dogs on the chart."Suppose the first ancestor of dog was created with all the DNA of the dogs included in that chart" - what does that mean? What does it mean to say the ancestral dog was created 'with' the DNA of the dogs on the chart?
Yes, let's say there are two, a male and a female."However the first generation puppies," - who did the ancestral dog mate with? Are there now two? This isn't a major issue, but it is unclear.
Good point."though having approx. the same amount of variety of DNA," - the same amount as what? Each puppy would have a distinct genetic code; are you saying the ancestral dog gave birth to, in the same litter, a genuine Chihuahua, Great Dane, Labrador, and all the other breeds? This doesn't match with what you later say about drifting families of dogs becoming the various breeds. So, are you saying that the puppies themselves have within them this variety of DNA - if so, what does "variety of DNA" mean? Is their DNA in some sort of quantum flux?
I was thinking that the ancestral male and female dogs would have a very large 'gene pool', so that the chance of defeats occurring from incestuous breeding would be greatly reduced. Is this fundamentally wrong?"would have no choice but to mate amongst themselves, which in itself would pose no problems with birth defects because they still have a large variety of DNA" - assuming the puppies have DNA, incestuous breeding wouldn't be abated. They would have inherited their DNA from their parents, with a number of mutations thrown in.
Non-natural-selection evolution?"However, after a number of generations, these dogs divided up into different families, and each family moved further and further apart from each other. After more and more generations, these families became different 'breeds' of dogs." - so, besides the wildcard of this "variety of DNA", it sounds like actual evolution, not an illusion. One ancestral species splits into several sub-species, the precursor to true speciation. If what you're describing isn't evolution, then what is it?
I was thinking along the lines that each distinct breed would eventually have a smaller gene pool, a bit like the Amish people in America. Alternatively, if Europeans can be traced back to a black-African type of ancestor, why can't a European couple have a black baby? I think it's because they no longer have black-African genes."However, now, none of these breeds have anywhere near the amount of variety of DNA that the first ancestral dog had." - so, the ancestral puppies, who eventually sired the genetically varied dog breeds, were more genetically varied than their more genetically varied offspring? How does that work?
OK, but what does that mean? It has the full genetic code of the Chihuaha alongside that of the Great Dane? How big would the dog be? Chihuahua-sized or Dane-sized?Yes, I meant the ancestral dog was created 'with' the DNA of the dogs on the chart.
These sorts of traits only code for a few alternatives - blonde or brown hair, for instance, or lobed or unlobed ears. Two white people won't be able to breed and produce someone who looks Asian.Good point.
I'm thinking of the ancestral female dog gave birth to, in the same litter, second generation dogs having DNA that included genuine Chihuahua, Great Dane, Labrador, and all the other breeds. For example, I have blond-hair genes from my father's side, but my hair is brown. My daughter, who is half Japanese, has very light-brown hair. So, I reasoning is that although I don't look as though I have blond hair genes, I do. In a similar manner, regardless of how the second generation dogs would look like, they (perhaps) could have DNA from which different breeds could stem from.
Fundamentally is the right word: the gene pool consists of all the breeding individuals of a population. Fewer breeders means a smaller gene pool. It doesn't mean that the individual has 'hidden DNA' that a given offspring will suddenly express.I was thinking that the ancestral male and female dogs would have a very large 'gene pool', so that the chance of defeats occurring from incestuous breeding would be greatly reduced. Is this fundamentally wrong?
Well, if there's some other selection process going on, it's not evident in the analogy - it sounds like this is a wholly natural process. Ironically, in reality, it wasn't natural selection, it was artificial selection.Non-natural-selection evolution?
Black skin is formed by how much melanin your skin makes, which goes back to genetics. Europeans don't have black babies because they don't have that gene. Not because the ancestral Africans had all human skin tones in their DNA, and modern 'races' inherited only one section - it's that the gene itself changed.I was thinking along the lines that each distinct breed would eventually have a smaller gene pool, a bit like the Amish people in America. Alternatively, if Europeans can be traced back to a black-African type of ancestor, why can't a European couple have a black baby? I think it's because they no longer have black-African genes.
There are also problems with mainating a viable long-term population from just two individuals. Far as we can tell, outside of bacteria, it can't be done.
The gist here is correct, although the details are a bit more complicated. There are multiple genes that control the production of melanin, and many have them have had mutations under positive selection in human populations outside Africa. For example, a mutation in the gene SLC24A5 is present in all Europeans but not at all in sub-Saharan Africans. The European version clearly started as a single, fairly recent mutation, which spread rapidly because it was advantageous to have lighter skin at high latitudes. In Africa, however, the gene shows every sign of not having recently come from a single copy, but instead of being been around in a large population for a very long time. (Basically, the European version resides on a single DNA background that looks identical in everyone in the population, while the African versions reside on many different backgrounds, showing a long history of mutation and recombination.)Black skin is formed by how much melanin your skin makes, which goes back to genetics. Europeans don't have black babies because they don't have that gene. Not because the ancestral Africans had all human skin tones in their DNA, and modern 'races' inherited only one section - it's that the gene itself changed.
There is only a 'melanin' gene, which in Africans is highly expressed, and in Europeans is not so expressed. Africans don't have within their DNA the genetic code for white people, nor did our African ancestors.
..it was advantageous to have lighter skin at high latitudes
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?