Evolution - Reality and Misconceptions
Discussion
E34-3.2 said:
Earth was covered of water for Years before the continents formed.
I have never seen that claim in any geology book. The leading theories states that earth began as a ball of rock and the first liquid water was formed/introduced around 200 million years later (via a combination of internal chemical reactions and comet/asteroid impacts).Earth has never been a 'water world' devoid of dry land.
That is my understanding too. Indeed, in its early history, the earth's surface was far too hot for liquid water to be able to remain liquid.. Indeed, there may have been periods where heavy rainfall vapourised before it hit the surface.
The question as to where the earth's water originated is not fully understood. It is thought that it is a combination of water molecules and/or the constituents of water (hydrogen and oxygen) being chemically bound in the rocks that made up the early earth and latter "top-ups" being provided by cometary and asteroidal/meteoritic impacts.
Whatever the mechansim, no liquid water could be sustained until the earth's surface had cooled down to the point where vapourisation would no longer be a serious issue.
The question as to where the earth's water originated is not fully understood. It is thought that it is a combination of water molecules and/or the constituents of water (hydrogen and oxygen) being chemically bound in the rocks that made up the early earth and latter "top-ups" being provided by cometary and asteroidal/meteoritic impacts.
Whatever the mechansim, no liquid water could be sustained until the earth's surface had cooled down to the point where vapourisation would no longer be a serious issue.
Gandahar said:
How do you judge long term evolution v modern day?
For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
Would they? So how one we have people around with genetic eyesight issues? For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
The beauty of the human race and what really sets us apart from the rest of the animals is our complex language and communications skills which allow us to cooperate with each other on very complex problems and share survival duties. The guy in the group who can't see particularly well may not be best placed on hunting d or guarding duty but another role in the community will be found for him, maybe he stays in the village banging the ladies whilst the men with good eyes are off hunting?
FredClogs said:
Would they? So how one we have people around with genetic eyesight issues?
The beauty of the human race and what really sets us apart from the rest of the animals is our complex language and communications skills which allow us to cooperate with each other on very complex problems and share survival duties. The guy in the group who can't see particularly well may not be best placed on hunting d or guarding duty but another role in the community will be found for him, maybe he stays in the village banging the ladies whilst the men with good eyes are off hunting?
Less selective about who they mate with?The beauty of the human race and what really sets us apart from the rest of the animals is our complex language and communications skills which allow us to cooperate with each other on very complex problems and share survival duties. The guy in the group who can't see particularly well may not be best placed on hunting d or guarding duty but another role in the community will be found for him, maybe he stays in the village banging the ladies whilst the men with good eyes are off hunting?
CrutyRammers said:
[Citation Needed]
https://news.nationalgeographic.com/news/2014/10/141030-starstruck-earth-water-origin-vesta-science/https://www.google.fr/amp/s/amp.ibtimes.co.in/eart...
https://www.google.fr/amp/s/www.newscientist.com/a...
FredClogs said:
Gandahar said:
How do you judge long term evolution v modern day?
For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
Would they? So how one we have people around with genetic eyesight issues? For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
The beauty of the human race and what really sets us apart from the rest of the animals is our complex language and communications skills which allow us to cooperate with each other on very complex problems and share survival duties. The guy in the group who can't see particularly well may not be best placed on hunting d or guarding duty but another role in the community will be found for him, maybe he stays in the village banging the ladies whilst the men with good eyes are off hunting?
Wiccan of Darkness said:
Misconception: Evolution occurs gradually, over millions of years.
Reality: Evolutionary steps occur rapidly.
It's not universally accepted I think, unless I've missed the consensus. There are adherents for both camps. Whilst the great catastrophes gave rise to lots of new species and killed off any number, these are few and far between. The movement of the continents, on the other hand, is rather pedestrian - and that's over-rating it - so the changes that gave rise to are slower.Reality: Evolutionary steps occur rapidly.
There is/was an argument that the dinosaurs, at least a number of them, were dying out due to climate change at the time of tunguska event. Their departure was hurried, like an unwelcome guest in the wee small hours after a party.
I've been reading a report in New Scientist, entitled Outsmarting evolution. I'll have to read it again as it takes a long while for things to sink in with me, but whilst its arguments are interesting and logical, come the next tunguska, all will be for nowt it seems to me.
Beating evolution is a bit like believing you are beating gravity by being in an aeroplane. Sooner or later it will have to come back down to Earth.
Wiccan of Darkness said:
Misconception: Evolution occurs gradually, over millions of years.
Reality: Evolutionary steps occur rapidly.
You're talking about the selection process happening over short periods of time, but the process of random mutation of the genes that become beneficial to be selected, obviously still takes an incredibly long time. Perhaps I'm guilty of using the nomenclature incorrectly, I have not studied this topic for some time, but when people talk about "evolution", I have always understood that they include this period where the gene must first develop. If this is correct, then "evolution" cannot happen rapidly, it is incremental (I would not say gradual) and it can take millions of years (with exceptions). Reality: Evolutionary steps occur rapidly.
If I am using the terminology incorrectly, that is to say you cannot use the word "evolution" to include this period of mututation, what then do you call the process where genes first arise from random mutation and are then selected for? Because my understanding was this was "evolution", and what you have just described is instead "selection".
That was my point earlier, which I appreciate you may not have read, regarding selective breeding of dogs. The domestication and selection for traits in the modern dog happened over an incredibly short period, and has yielded much diversity, but the genes were already present in the population. The fifteen thousand years or so in which we have bred dogs is insuffficient for the genes to first mutate then be selected.
Derek Smith said:
It's not universally accepted I think, unless I've missed the consensus. There are adherents for both camps. Whilst the great catastrophes gave rise to lots of new species and killed off any number, these are few and far between. The movement of the continents, on the other hand, is rather pedestrian - and that's over-rating it - so the changes that gave rise to are slower.
There is/was an argument that the dinosaurs, at least a number of them, were dying out due to climate change at the time of tunguska event. Their departure was hurried, like an unwelcome guest in the wee small hours after a party.
I've been reading a report in New Scientist, entitled Outsmarting evolution. I'll have to read it again as it takes a long while for things to sink in with me, but whilst its arguments are interesting and logical, come the next tunguska, all will be for nowt it seems to me.
Beating evolution is a bit like believing you are beating gravity by being in an aeroplane. Sooner or later it will have to come back down to Earth.
The Tunguska Event is a recent (fairly minor) impact - 1908 - and has nothing to do with dinosaur extinction.There is/was an argument that the dinosaurs, at least a number of them, were dying out due to climate change at the time of tunguska event. Their departure was hurried, like an unwelcome guest in the wee small hours after a party.
I've been reading a report in New Scientist, entitled Outsmarting evolution. I'll have to read it again as it takes a long while for things to sink in with me, but whilst its arguments are interesting and logical, come the next tunguska, all will be for nowt it seems to me.
Beating evolution is a bit like believing you are beating gravity by being in an aeroplane. Sooner or later it will have to come back down to Earth.
I presume you mean the Chixilub Event which happened 65 million years ago and seems to have been influential in the disappearance of the dinosaurs - as well as about 75% of other higher animal species that existed at that time.
There is no genuine evidence that it was the asteroid impact of 65 million years ago that actually caused dinosaur extinction - but dinosaurs do disappear from the geological record around 65 million years ago.
That's assuming you don't include birds as dinosaurs - which they increasingly seem to be. In that case, dinosaurs never really did become extinct as they are still around.
Prof Prolapse said:
You're talking about the selection process happening over short periods of time, but the process of random mutation of the genes that become beneficial to be selected, obviously still takes an incredibly long time. Perhaps I'm guilty of using the nomenclature incorrectly, I have not studied this topic for some time, but when people talk about "evolution", I have always understood that they include this period where the gene must first develop. If this is correct, then "evolution" cannot happen rapidly, it is incremental (I would not say gradual) and it can take millions of years (with exceptions).
If I am using the terminology incorrectly, that is to say you cannot use the word "evolution" to include this period of mututation, what then do you call the process where genes first arise from random mutation and are then selected for? Because my understanding was this was "evolution", and what you have just described is instead "selection".
That was my point earlier, which I appreciate you may not have read, regarding selective breeding of dogs. The domestication and selection for traits in the modern dog happened over an incredibly short period, and has yielded much diversity, but the genes were already present in the population. The fifteen thousand years or so in which we have bred dogs is insuffficient for the genes to first mutate then be selected.
But it isn’t always a question of individual genes, it can be a combination of genes. If changing circumstances mean that those individuals who by chance have a particular combination of existing genes and therefore a particular characteristic, perhaps a long neck, start to have an advantage, then those genes and that characteristic will become more common. Once the average neck length has increased there will be more individuals with very very long necks who may turn out to have a greater advantage.If I am using the terminology incorrectly, that is to say you cannot use the word "evolution" to include this period of mututation, what then do you call the process where genes first arise from random mutation and are then selected for? Because my understanding was this was "evolution", and what you have just described is instead "selection".
That was my point earlier, which I appreciate you may not have read, regarding selective breeding of dogs. The domestication and selection for traits in the modern dog happened over an incredibly short period, and has yielded much diversity, but the genes were already present in the population. The fifteen thousand years or so in which we have bred dogs is insuffficient for the genes to first mutate then be selected.
It’s the characteristic, the phenotype, that’s being selected not the genes.
FredClogs said:
Gandahar said:
How do you judge long term evolution v modern day?
For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
Would they? So how one we have people around with genetic eyesight issues? For instance, just taking man for an example, in the old days people with poor sight would die out. Now we just get contact lenses.
The beauty of the human race and what really sets us apart from the rest of the animals is our complex language and communications skills which allow us to cooperate with each other on very complex problems and share survival duties. The guy in the group who can't see particularly well may not be best placed on hunting d or guarding duty but another role in the community will be found for him, maybe he stays in the village banging the ladies whilst the men with good eyes are off hunting?
We tend to be long sighted in youth and become progressive short sighted as we age. It is feasible that evolution selected for that (no idea if it's actually been studied), or it might not be a sufficient disadvantage to be deselected. We do know that women generally have a shallower depth of focus than men. Not a survival problem and perhaps an advantage given what we know of ancient gender roles, with women tending to be nurturers & gathers vs an ancient men tending to be hunters.
Evolutionary survival of the fittest resulted in that change? Plausible. Evolution might have selected that, or not found it a problem with fitness. The long sighted young being better equipped to hunt vs older crafters being better able to perform close up intricate work like napping spear tips. Yes it is a bit chicken and egg, but does seem to show the attribute of a positive feedback loop we see throughout evolution.
We do know that night hunting animals generally have more rods than cones, because rods are better at detecting outlines and movement in low light. While day hunters have better colour detection. Evolution is going to find a balance.
It is plausible that things like colour blindness are the same, perhaps somebody can answer the question; is colour blindness really a matter of a different advantage vs a disadvantage. It might be similar to cystic fibrosis or sickle cell.
Degenerative things like cataracts are probably a case of ancient ancestors never really living long enough for a predisposition to that to exert a strong selective pressure, compared to everything else.
Edited by 4x4Tyke on Wednesday 5th September 12:48
Dr Jekyll said:
But it isn’t always a question of individual genes, it can be a combination of genes. If changing circumstances mean that those individuals who by chance have a particular combination of existing genes and therefore a particular characteristic, perhaps a long neck, start to have an advantage, then those genes and that characteristic will become more common. Once the average neck length has increased there will be more individuals with very very long necks who may turn out to have a greater advantage.
It’s the characteristic, the phenotype, that’s being selected not the genes.
You're misunderstanding me, and I also believe you're incorrect in your closing statment, it's widely held that selection happens at the level of the gene, not the phenotype. That's quite important, and I believe the explanation is given in R.Dawkins book "The selfish gene", otherwise we would not see the distribution of genes and traits that we do, especially traits like altruism. It’s the characteristic, the phenotype, that’s being selected not the genes.
https://en.wikipedia.org/wiki/Gene-centered_view_o...
That aside, it doesn't matter in context whether it's a combination of genes, which themselves require expression, required for each phenotype, there's only about 20,000 genes, there's no where near enough for each to be associated with a characteristic in person, so we know it's complicated.
But whether or not you require genes A, B, and C, or just are waiting for gene C, you still need to wait for the gene coding errors to give rise to it. Which takes a very long time.
Think of it like pulling letters out of the scabble bag, which is your gene pool. You need to spell "ABC", but it's currently full of A's and B's only. So it doesn't matter how many letters you pull out of that bag, or how many points you'll get for that combination of letters, until nature puts a C in there by mutation, you'll never spell "ABC".
Maintaining the analogy, my point was that I understand, that the process of getting all the letters in the bag, and then spelling the letter. Is one process ("Evolution"), the process of just pulling out the existing letters and spelling words ("Selection"), is simply part of it.
If that makes sense?
ash73 said:
How do you square that with the Cambrian explosion? Obviously it's a question of how many million years is enough, but 25 Ma seems a very short period of time for virtually ALL body formats to evolve.
I'm not "that sort of biologist", so unfortunately I can't comment on specific examples, but the rate of evolution (if we are including mutation of genes) is comparitively slow compared with selection alone, but it is not fixed. I did caveat myself with that earlier.Just as an example of how the rate can change (not specific to the Cambrian explosion, I simply do not know) the mutations in your DNA happen for a number of reasons but transcription errors as result of part of the cell replication process are important. Too many errors however, and the cell will die, so there are cellular machinary which limit the error rate.
But what happened before that protective machinery evolved or if it became less effective? The mutation rate would increase, cellular death would presumably be higher, particularly in more complex organisms, but again just as a for instance, what if you had simple, robust organisms, which bred quickly and with little selective pressures? They could in theory have viable survival rates. Not just that but you'd presumably have a very diverse range of traits. Subsequent generations of these organisms could even then develop more accurate gene transcription, meaning such changes reduced in frequency, so now the diverse traits are effectively fixed in the population.
I'm not saying that's what happened, I'm just saying that even with a rudimentary understanding of DNA you can see how such rate changes are feasible. If increasingly unlikely as organisms become more complex.
Edited by Prof Prolapse on Wednesday 5th September 12:19
Edited by Prof Prolapse on Wednesday 5th September 12:21
Prof Prolapse said:
Wiccan of Darkness said:
Misconception: Evolution occurs gradually, over millions of years.
Reality: Evolutionary steps occur rapidly.
You're talking about the selection process happening over short periods of time, but the process of random mutation of the genes that become beneficial to be selected, obviously still takes an incredibly long time. Reality: Evolutionary steps occur rapidly.
I see evolution as the entire process, it includes both the big step changes seen in the fossil record between periods of relative equilibrium and with genetic drift. We also see evidence of genetic drift through speciation through the biological kingdoms. The big changes in kingdoms Animal/Plant for example are huge now, but in their earliest forms were far smaller. There are genes and mutations that exist across kingdoms which is how we know if they have a common source or know they arose independently/separately.
The thing about the fossil record is will only reveal the big changes easily, which is why it suggests punctuated equilibrium.
Genetic drift will reveal big changes but it will also reveal the small changes, which is why we see periods of relative stability as specific traits as optimised by survival of the fittest.
That's my understanding anyway.
Evolution can happen pretty rapidly even with a relatively low germline mutation rate, given enough individuals in a population, and a diverse range of selection pressures. There are loads of examples of adaptive stress resulting in evolutionary change in just a few generations.
The Cambrian explosion was probably an example of a number of rapid changes in the environment (O2 concentration, ozone levels, temperature etc) that created new biochemical space and therefore new ecological niches for organisms to exploit.
Even so 70-80 million years is quite along time. That's a lot of generations given that the reproductive rate for many Precambrian organisms was measured in hours.
Whenever I'm told that evolution is grindingly slow I remember that highly complex eyes have evolved many times independently, and current estimates are that even a complex eye like ours could evolve from a cluster of light sensitive cells in around 364000 years (that's the blink of an eye so to speak).
http://rspb.royalsocietypublishing.org/content/256...
The Cambrian explosion was probably an example of a number of rapid changes in the environment (O2 concentration, ozone levels, temperature etc) that created new biochemical space and therefore new ecological niches for organisms to exploit.
Even so 70-80 million years is quite along time. That's a lot of generations given that the reproductive rate for many Precambrian organisms was measured in hours.
Whenever I'm told that evolution is grindingly slow I remember that highly complex eyes have evolved many times independently, and current estimates are that even a complex eye like ours could evolve from a cluster of light sensitive cells in around 364000 years (that's the blink of an eye so to speak).
http://rspb.royalsocietypublishing.org/content/256...
Prof Prolapse said:
I'm not familiar with all of the terminology you're using but a change of "rate" is observably true as I understand it. I tried to provide a fictious explanation of that above.
If I disagree with Wiccan, it's only because of a semantic, but I believe an important one.
The terms I've used largely follow the natural language meanings, the value for me is in the discussion, but I'm happy to elaborate and be corrected because then I learn something new as well.If I disagree with Wiccan, it's only because of a semantic, but I believe an important one.
Gradual evolution - slow steady change from one to another, like the foxes example discussed earlier
Punctuated equilibrium - slow steady changes interspaced with a period of rapid change, the emergence of new biological kingdom like Plants for example. Equilibrium doesn't imply static but that all the key species are in a typical evolutionary 'arms race',
Genetic drift is the steady rate of mutation and distribution of those mutations, its a big topic though and I suspect Wiccan's knowledge of that area will far greater than mine given his previous revealed expertise. He will probably use the proper word for that, Alleles. In my less specialist understanding, Alleles are the collection of possible mutations that can occur on a specific gene. Some like hair colour have many variations, some like sickle cell few. We can determine from the number of mutations and their distribution how old these changes are.
The biological kingdoms are the main types of life Animal, Plant, Protozoa etc. and each punctuation is the emergence of a new branch in the tree. At the base of the tree the changes are slight, the higher up the tree the bigger the apparent difference and more evident in the fossil record. Imagine how hard it would be to distinguish a fossil protozoa from a bacteria, even with an electron microscope that has got to be in the realm of pretty damned hard.
Edited by 4x4Tyke on Thursday 6th September 08:45
Eric Mc said:
The Tunguska Event is a recent (fairly minor) impact - 1908 - and has nothing to do with dinosaur extinction.
I presume you mean the Chixilub Event which happened 65 million years ago and seems to have been influential in the disappearance of the dinosaurs - as well as about 75% of other higher animal species that existed at that time.
There is no genuine evidence that it was the asteroid impact of 65 million years ago that actually caused dinosaur extinction - but dinosaurs do disappear from the geological record around 65 million years ago.
That's assuming you don't include birds as dinosaurs - which they increasingly seem to be. In that case, dinosaurs never really did become extinct as they are still around.
Yes, that's the tunguska event I was talking about. I presume you mean the Chixilub Event which happened 65 million years ago and seems to have been influential in the disappearance of the dinosaurs - as well as about 75% of other higher animal species that existed at that time.
There is no genuine evidence that it was the asteroid impact of 65 million years ago that actually caused dinosaur extinction - but dinosaurs do disappear from the geological record around 65 million years ago.
That's assuming you don't include birds as dinosaurs - which they increasingly seem to be. In that case, dinosaurs never really did become extinct as they are still around.
I don't see how we can claim birds as dinosaurs. Surely they had evolved into a separate species before the Chixilub event. Whatever, the main point is that when there's no clutter, with animals not fighting for elbow room, evolution increases speed over its normal response.
There seems to be acceptance that the asteroid/comet was instrumental in the extinction of the dinosaurs although there's as much acceptance that the climate was changing due to volcanic activity as well. I'd charge both.
The fact that we know there already were obvious "birds" for quite a while before the asteroid impact does not mean that they were not just another type of dinosaur. The recognised first bird found (so far) is Archeoptryx - which is from 150 million years ago. Archeoptryx is really the first dinosaur we found that possessed feather. Because it had feathers, it was classified as a bird. In every other respect, it's a dinosaur. We now know many dinosaurs had feathers.
There is plenty of evidence that birds and dinosaurs are extremely close evolutionary speaking. Indeed, since the mid 1960s and the work of the late John Ostrom and many since, many paeleontoligists have come to the conclusion that there is not really a significant difference between certain dinosaurs and modern birds. Only last week there was a major news story that spoke about new genetic evidence that closens the links even more.
It must be remembered that "dinosaur" is actually a rather incorrect "catch all" name used for what was really a very wide variety of different lines. The two main groups of dinosaurs were the suarischia (lizard hipped) and the ornithisca (bird hipped).
It was spotted quite early on (mid 19th century) in the study of dinosaur physiology that there were two distinct groups which could be identified by their different types of hip structures. One group had a pelvis pretty much the same as modern birds. The other had hips closer to that of modern lizards. We now know that many dinosaurs had the following features -
bird type pelvises
feathers (which we can now see were pretty much identical to modern bird feathers)
hollow bones filled with air sacs
four chambered hearts (something associated with endothermic control of body temperatures - an avian characteristic)
lack of teeth
beaks
All of these characteristics are very typical of birds. Indeed, if some small dinosaurs were still around today, they would probably be classified as flightless birds. Every time I look at a blackbird darting across my lawn, it screams "dinosaur" at me.
I do agree that what caused the "extinction" of the dinosurs (notwithstanding that they aren't all extinct as per above) is attributable to multiple causes with an asteroid impact impact being just one factor rather than the only one.
There is plenty of evidence that birds and dinosaurs are extremely close evolutionary speaking. Indeed, since the mid 1960s and the work of the late John Ostrom and many since, many paeleontoligists have come to the conclusion that there is not really a significant difference between certain dinosaurs and modern birds. Only last week there was a major news story that spoke about new genetic evidence that closens the links even more.
It must be remembered that "dinosaur" is actually a rather incorrect "catch all" name used for what was really a very wide variety of different lines. The two main groups of dinosaurs were the suarischia (lizard hipped) and the ornithisca (bird hipped).
It was spotted quite early on (mid 19th century) in the study of dinosaur physiology that there were two distinct groups which could be identified by their different types of hip structures. One group had a pelvis pretty much the same as modern birds. The other had hips closer to that of modern lizards. We now know that many dinosaurs had the following features -
bird type pelvises
feathers (which we can now see were pretty much identical to modern bird feathers)
hollow bones filled with air sacs
four chambered hearts (something associated with endothermic control of body temperatures - an avian characteristic)
lack of teeth
beaks
All of these characteristics are very typical of birds. Indeed, if some small dinosaurs were still around today, they would probably be classified as flightless birds. Every time I look at a blackbird darting across my lawn, it screams "dinosaur" at me.
I do agree that what caused the "extinction" of the dinosurs (notwithstanding that they aren't all extinct as per above) is attributable to multiple causes with an asteroid impact impact being just one factor rather than the only one.
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