the textbook example of evolution is the elongation of the goat/whatever’s neck into that of a giraffe, as over subsequent years descendents adapted to leafs being at heights in certain areas.
evolution is directed, over generations, fine tuning species to its environment.
the way I see it working (very crudely) is that experience of the environment cause the animals to learn certain features that they would desire (by instinct) their successors to have.
this makes sense to me. but how is this information transmitted? presumably through genes, because any other form of learning would happen after birth, and thus would not result in physical mutation.
but arent one’s genes like one’s fingerprints? Uniquely our own? A sample at birth would be the same as a sample on death. There is no increase/decrease of information that is transmitted.
How then is experience transmitted over generations?
Who knows? As far as I'm aware, this process has yet to be discovered and documented. There's, of course, the idea that, by normal amounts of mutation, offspring are produced that have a certain characteristic that makes their lives easier, or possible. The ones that don't have this trait, die off, unable to breed and so the new trait is the only one that carries through. The success of the more advanced creature causes its traits to sweep through the population. So, rather than an intelligent creation of the ideal, adapted offspring, a lot are produced, and ones that can adapt, live on, adn those that can't, die off. And if the parents have favourable traits, they're more likely to produce more offspring than those that don't. Natural Selection, survival of the fittest. Hit and miss, essentially. Who knows, though, it's all theory. :)
So, as far as I'm aware, the idea isn't that a certain trait is (sub)consciencely put into offspring, but rather, the ones with favourable traits survive to carry it onwards.
My understanding is similar to RTs. Species are not genetically homogenous. In other words, you can be in the same species but not be genetically identical. Sub-groups within a species may have certain genetic characteristics that are unique to them. In some cases, those unique genetic differences make it easier or harder to cope with the environment. Those with the positive genetic traits survive and those with the negative ones don't. Then, mutations also occur within the gene pool of the survivors. The same thing happens again. Over millions of years, this process of mutation, survival, mutation, survival changes the characteristics of the species.
So it's not so much that the environment causes the mutation. It's that the population that has the mutation survives in the environement.
A classical example of this that is drummed into peoples' heads (precisely what i am going to do right now) is that of Gypsy moths at the time of industrial England (circa mid-1800s). The majority of moths were light-coloured; there was a minority that happened to be coloured of a dark grey variety (these ones were at a disadvantage due to their dark grey colour and inability to blend in with their environment). At the time of the industrial revolution in England, the pollution levels all over the region increased to such an extent that the bark on the trees started to be covered with soot and ash. The light-coloured moths, that previously had been in abundance and were considered the dominant species, started to experience a sharp decline in their numbers, because their colour (that previously had been an asset) was now a liability. Even though they were the predominant species, that didn't help. The dark grey moths, that happened to possess this different adaptive characteristic, were the ones who started to flourish because their colour allowed them to blend in with the soot and ash on the tree barks.
blah blah blah. What i am trying to say is that it doesn't really matter which species is really the strongest, so much as which individual members of the species possess those quirky characteristics that can help them to adapt. The animal most suited to "fit" in its natural environment, will be the one that survives.
Anyways...blah blah just wanted to add that in to tie it in with what MyVoice stated regarding It's that the population that has the mutation survives in the environement.
I never heard that story Nadia. Thanks. It's a great example.
Evolution also makes you wonder about certain things that we call mutations.
One that's always interested me is the sickle cell trait in blacks and the Tay Sachs trait in Jews. It's conventional wisdom that these traits are harmful and negative to those who have them based upon todays environment. But why does such a relatively good size percentage have these genetic traits? Maybe the sickle cell or Tay Sachs traits actually could be positive in some future generations because they allow those who possess them to better cope with the environment of the time.
In trying to wipe these things out today are we perhaps unintentionally interfering with natural evolutionary stages that would ensure survival in some future environment.
well, till short i used to be inclined towards the evolution theory and its assests. However, i've been reading through some recent literature by scientists and philosophers (D. Berlinski and co.) have made me question the theory. And i have to say the role of 'natural selection', and 'survival of the fittest' etc are quite peculiar. I don't think they exist, or at least in the form they are put forward classically. It would take too long to bring forward all the arguments against these phenomena, but I'd say that it's about time the evolution theory is subjected to new scrutiny and evaluation. Curiously enough, this is one of the few theories which hasn't shown and progress or criticism for a long time
There isn't one accepted evolutionary theory, you have your natural selection of Darwin and others, then punctuated equlibria then all the stuff that came out of the Ediacara fauna find.
What we do know is that not all species around today were around in the Geological past and not all from the past are around today.
Variations on the above theories with a few new ideas thrown in will keep this debate active and no doubt there is an element of more than one process in action.
hey Thap, I was implicitly hoping you would show up. i was interested in ur opinion about this. Have you read literature of Berlinski??? I can try to send you the article im talking about. or try to outline the major points here
This is not really my field these days, but I have colleagues very much involved.
Although I have read some of Berlinski's stuff from the late 90's published in the Commentary magazine.
He seems to sum up what's going on pretty well but fails to get a clear emphasis across on what he's actually purporting. Maybe it was his commentaries only, he reads like a movie critic with failed aspirations of being a director.
I must admit I got pretty lost in his semantics; maybe he has improved and unified his thought.
All I'll say is that the theory of evolution is very much evolving and adaptation should not be ruled out and Eldridge and Gould's punctuated equilibria are also key, IM humblest of HO.
However, I always find in such discussions ones own interpretation and resulting precis are always more useful than the trusted established example of memorising by rote and repeating, so fire away.
RTWolf, MV, Nadia, you're right. And I should've known this since its basic evolutionary theory.
What confused me though was the progressive elongation over generations of the goat/whatever's neck instead of short->long. Is that because over time the giraffe got to mate with more hybrids, causing the hybrids to get longer necks?
a long neck in a population of normal-necked animals occurs as a genetic abberation (mutation). if having a longer neck enables the animal to be more healthy/viable, it would have more offsprings than the average animal in its population. the genetic abberation gets transmitted to its offsprings. over time, animals with longer necks dominate the population since they are more healthy/viable and the "normal-necked" animals lose out.
in the case of giraffes, longer necks enabled grazing off trees, as opposed to just shrubs at body height.
also, its true that everyone's genetic makeup is unique. but thats only half the truth. you share half your genes with your dad and the other half with your mom identically (well almost identically - during gamete formation, something called crossing over takes place in chromosomal pairs, which leads to some added differences in your genes from those of your parents). so thats where the information transfer lies. mutation/crossover adds changes to the information.
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One that's always interested me is the sickle cell trait in blacks and the Tay Sachs trait in Jews. It's conventional wisdom that these traits are harmful and negative to those who have them based upon todays environment.
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MV there have been studies linking the heterozygous sickle cell trait with reduced incidence of Malaria in African countries. It has to do with the life cycle of Plasmodium falciparum the malaria causing parasite. I don't know about Tay-Sachs trait...will read up to see if any links have been found so far.
MV there have been studies linking the heterozygous sickle cell trait with reduced incidence of Malaria in African countries. It has to do with the life cycle of Plasmodium falciparum the malaria causing parasite. I don't know about Tay-Sachs trait...will read up to see if any links have been found so far.
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Thanks for that info. It's fascinating that we have a genetic mutation that I guess has positive effects in the population if they live in one part of the world where Malaria is prevalent. The trade-off is that you might die younger in places that don't have malaria.
ravage i've wondered that myself many times as well...the exact same thing...
i don't know if i really believe in the theory of evolution...specially for humans...for example now with geographical dislocation of human populations all over the globe to places with different physical and climatic conditions, with different resultant needs for humans respective to their location, will natural evolution not become a very haphazard process with debatable usefulness?
I am more interested in the geological processes have occurred that are supported by various evolutionary niches.
For example, look at the types of paleo-flora and fauna fossils found on the various continents. The classic example is Glossopteris, an ancient plant that existed during the Palezoic, the same time when Pangea was supposed to have existed. Geologists have found this tropical plant fossil on such continents as South America, Africa, India (it was its own continent at one time), and recently it was discovered in Antarctica! That is freaking amazing to me. Obviously, Antarctica was once located much closer to the equator.
The point I am actually trying to make in accordance with the thread ;) is that there has always existed variation in the locations of plants and animals. Evolution is not a purposeful event. (I am a fan of Steven J. Gould, as well) It seems to be no more than accidental mutations that re-occur in a population. The mutation may be successful or not. We either have survival or extinction. Thank Heavens evolution is not instantaneous ;)