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Author | Topic: The Koala, Lamark and Epigenetics | |||||||||||||||||||||||||||||||||||||||
RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Again, welcome to the fray, LamarkNewAge.
... Wouldn't the data suggest that the most logical conclusion is that this narrow diet was acquired by behavior of a koala during his/her life and somehow (by say epigenetic means?) this trait got passed down into succeeding offspring and it got locked into the animals DNA later down the generational tree? ... My first impression is that modern evolutionary theory is sufficient. There are many example where plants evolve with specific animals\insects\etc to mutual benefit: the plant gets fertilized or seeds distributed in exchange for providing a special diet, and the consumer gets special food in exchange for assisting the plant to grow (fertilizer) and spread.
Could a bunch of random DNA mutations explain the koala diet. I'm asking if the "neo-Darwinian" theory (using Gregor Mendel theory to supplement Darmin's theory) really does best explain this situation.... Yes, because evolution involves selection as well as random variation. What I don't see is a reason to assume a neo-lamarkian explanation, why the data would suggest the diet isolation would be an acquired trait. Can you explain your thinking here? What would be the environmental chemical that would cause this and what would be the source for it? Enjoy Edited by RAZD, : No reason given. Edited by RAZD, : .by our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... A random mutation (or series of mutations) that lead to such a narrow diet that by coincidence only enables digestion of a single type of plant just doesn't seems to fit what must go on in nature (so my thinking goes anyway). ... Again you are forgetting selection. Selection is non-random, and it is the other part of evolution that leads to adaptation. I can go into more detail when I get home (my tablet not that friendly to posting linked information). Enjoy PS - type [qs]quotes are easy[/qs] and it becomes:
quotes are easy or type [quote]quotes are easy[/quote] and it becomes:
quote: by our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined:
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... I agree that there are many discoveries still to be made in the field of evolutionary biology and they will be incorporated into the theory as they are understood. ... Building on what has gone before ... Darwin's theory of origin of species via natural selection has not been invalidated, rather it has been expandedas we know more. Mendle's genetics was not known by Darwin, but were incorporated as the explanation of variation that were observed. With the melding with genetics in the 50's. Any new theory will need to explain all the evidence currdntly explained by the ToE - it will default to the current explanation for that evidence - and thenprovide testable predictions for new evidence. That is how science works. So far I see no testable proposition for a neo-Lamarkism as discussed here. Or any reason to consider one. Enjoyby our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
In the case of mammals, there are plenty of more conventional methods for passing along information. Mammals tend to spend time hanging out with mama which means that behavioral information can be passed on by teaching/learning. Indeed, and if such teaching/learning fails in one generation, it is lost. Without laguage such things can only be taugh through demonstration. Enjoyby our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined:
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Birds do a lot of training also, and apparently with some birds like parrots vocalization is also involved. Any species where the young follow and watch and imitate parents or older members would likely be learning behavior that has been beneficial or neutral to survival or reproduction. Any behavior that would be lethal or injurious would tend to be self eliminating. This is the only way I can see how purely behavioral traits can be passed from one generation to the next: there has to be a teaching\learning cycle. The classic lamarkian example of the giraffe neck elongating from use stretching for food fails to have a path to pass on that elongation (but selection for longer neck genes does have a path). Another classic lamarkian example of a blacksmith being big, brawny and muscular from use of muscles is not so clear cut, as learning the trade would involve (teaching\learning) muscle building, ... but there would also likely be some selection of apprentices for those with more natural (genetic) disposition to be muscular doing better at the job than those less naturally (genetic) endowed, so observed long term trends would see beefier and beefier blacksmiths. Stretching the neck out does not significantly change the length of the neck vertibrae, but continual body building can significantly alter the size of the muscles - one is bone and the other is tissue.
I am most fascinated by complex behaviors that are programmed into the genes of insects. They seem to work as cascade effects where a stimulus triggers a series sensory signals and behaviors. Many of these behaviors seem to be similar to complex "if > then" loops in computer programs. When I am in the field with other Odonatists we endlessly discuss dragonfly behavior and how it is programmed. The way I see this, is that such "programmed" behavior is "learned" by by the species through selection (genetic) of those who successfully (survived, improved reproduction) passed the stimulus reaction test, and over time the accumulation of such programmed behaviors become more complex. This would be comparable to "teaching" AI behavior to randomly programmed robots by providing a series of stimulation reaction test and selecting the programs that made the desired choice. Enjoyby our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Getting back to you as promised:
Selection for an animal going blind happens when the animal species will live in a (nearly or)100% dark environment. It takes a lot of molecular energy for eyes to (be able to) see so selection can and does lead to that gene-for-seeing getting turned off in increasingly large numbers of the species over time. Indeed, and there are many many many similar examples (fish, shrimp, cockroaches, spiders, etc etc etc).
But how can 1 million different types of food to possibly eat(represented in an animal by 1 million hypothetical genetic variants) out of 1,000,001 genetic variant possibilities in time get driven out of the gene pool of an animal. ... Each species occupies selected habitats, in that they become adapted to the ones that are available and choose among those by being better at surviving and reproducing in them. Each habitat has limited available resources rather than millions, and so species make the best of the resources available to them. Koalas cannot fly to North America, for instance, so they are limited to habitats near them, ones dominated by eucalyptus plants. In addition there is an ecological equilibrium distribution for habitats -- they can only support a relatively fixed number of grass grazers (resource limited) and a (smaller) relatively fixed number grass-grazer predators (also resource limited). It doesn't matter what species the grazers or predators are. This has been demonstrated by experiments on islands where all the existing species were documented and then removed, and new ones allowed to colonize the island: after a few years the same ratios of species in the habitat reached the same basic equilibrium as existed previously. (E.O.Wilson) So there are only a few available resources in a given habitat, and some will be more competitively guarded\accessed than others.
... know it CAN HAPPEN according to neo-Darwinian theory but how DOES it happen in practice? ... A slow moving herbivore with little aggressiveness or defensive ability (koala, sloth, etc) would tend to be driven to what would be marginal resources for the other species. This limits their access to types of resources even smaller. Adaptation over generations would improve their ability to use such resources and become specialists in it compared to other species.
... Eventually, the molecular mutations won't do what they might be capable of. They can but won't keep on eliminating all the various DNA codes except the one that allows just one (!) type of food to eat. ... What is to prevent it? There is no drive for mutations to occur just so they can benefit a species -- they are random. What causes the adaptation process to move in a direction of benefit to the species is selection of those mutations that offer the best ability to survive and reproduce. That selection process has no stop button. Evolution is a slow stagger towards adaption to any specific habitat:
Imagine walking across the US, starting in Boston with a "habitat goal" of getting to San Francisco. For each step you throw 3 dice, where the faces are marked with degrees azimuth (0°, 60°, 120°, 180°, 240°, and 300°) and you can select the one closest to your path to the "habitat goal" ... you will get there eventually even though you may have to take an occasional back-step and many side-steps. Your chances of getting there without selection is virtually zero.
... I agree that it might be molecularly efficient and AGAIN I agree that it is genetically possible. Indeed, it is possible with appropriate mutations to change a mouse into (something similar to) an elephant. Their basic genetics are the same, just different variations in the patterns of the DNA. But again, without selection the chances of this occurring is virtually zero.
(Lamarkian?) Epigenetics is far faster than the lone neo-Darwinian mechanism and might follow a pattern in nature we can picture if we imagine how a chicken learned how to cross the street (it just learned!). ... Epigenetics is not learned behavior either. Epigenetics is the effects of the environment on the development of the individual. For example the sex of an alligator is determined not by DNA but by the temperature of the nest during incubation (something monitored fairly closely by the mamma gator) where variations within the nest result in some males and some females. By contrast the female displays learned\imprinted\instinctive behavior in choosing the temperatures so that the average ration is 1 male to 5 females, a ratio that apparently provides for long term survival of the species (more males = fewer females = fewer alligators; less males = more females = more not reproducing = fewer alligators). Other epigenetic effects are more often observed with birth defects, such as the notorious Thalidomide drug effects circa 1957. Usually the epigenetic effects occur through hormone imbalance (too much or too little) and the (chemicals in the) environment is capable of altering the hormonal balance of the mothers during pregnancy. DDT and bird egg shell thickness\strength. The "taming" of the Siberian silver foxes that you mention occurred through a generations long experiment where the only actor selected for was relative tameness. The purpose was to develop a fox that was easier to raise to provide fur for the industry. The result was tame foxes, as intended, but with unintended changes to the ears, tail, voice and especially to the fur coloration (which rendered the "product" unusable for the fur industry). This is apparently because the amount of adrenaline was lower in the selected individuals and that affected their growth during development. Similar color\behavior patterns are seen in other domesticated animals.
... How do migratory birds know where to fly (even if their parents weren't around to teach them)? How do we learn anything? Random mutations? We just learn. We learn by what has been tested over generations to be better for survival. When we talk about basic instinct\reflex we say it gets imprinted into the species behavioral matrix through a series of random "tests" -- behavior that leads to fatality is eliminated, behavior that permits survival and reproduction continues. Over time this approach builds up quite complex behavioral patterns (dancing bees, mating cranes, etc) all being tested by multiple trial and error tests selecting what works from what doesn't. When we talk about learned behavior we say it is learned from another individual by observation and imitation, it is a conscious learning process, but it too is the result of a series of random "tests" -- behavior that leads to fatality is eliminated, behavior that permits survival and reproduction continues. Or the behavior is survival neutral but preferred: Blue Planet Biomes - Japanese Macaque
quote: New learned behavior requires innovators that add to the behavioral matrix those that are beneficial or neutral. If it works then "add to cart" and if it doesn't then discard it. Over time this approach also builds up quite complex behavioral patterns, and probably the most complex developed to date is our ability to record and compare results. Enjoyby our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Minor nitpick - bone is also tissue and, at least in mammals*, can also be altered significantly by training. I thought bone mass etc was more diet driven, but okay IB corrected. But in any case the changes are not passed to the offspring genetically, and can only be transmitted through learned behavior. Lose the trainer(s) and the changes will be lost. Thanks.by our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Curiously, I ran across this article the other day:
quote: Not affecting the genes but affecting the development of the phenotype. Enjoyby our ability to understand Rebel☮American☆Zen☯Deist ... to learn ... to think ... to live ... to laugh ... to share. Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
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