Naked Science Forum
General Science => General Science => Topic started by: Ozze on 11/03/2008 05:50:54
-
Im having problems with Darwin and Lamarck. Ive been researching On darwin's and Lamarck's theory but, every site seems to be complicated to read.
Can anyone please help me seeing as i am very clueless on this topic.
I am suppose to Compare and contrast Darwin and lamarck's theory of evolution aswell as lineus's ideas of classification.
-how are these ideas connected.
how are they different?
Why is it important to study humans + human evolution?
-
Darwin based his idea of evolution on sex (i.e. he suggested that evolution went about because males and females selected sexual partners that were beneficial to their children, either through deliberate choice, or because those without the beneficial traits simply did not survive).
Lamarck suggested that as organisms (e.g. animals) lived their lives, they changed their physique throughout their lives, and the offspring would inherit the changes that occured during the parents life.
As an example:
Suppose one had a proto giraffe that lived in an environment where he had to reach up high to get the best food.
Lamarck said that the proto-giraffe would have had to stretch its neck, so when its children were born they would have long necks.
Darwin said that no matter whether the proto-giraffe spent all its life stretching its neck or not, its offspring would have the same length neck. On the other hand, those proto-giraffes that naturally had shorter necks would not be able to feed as well, so they would either die young, or not have as many children, so those proto-giraffes that naturally already had slightly longer necks would have more children, so the average length of the next generation of proto-giraffes would have had slightly longer necks through selective breeding, rather than by inheritance of life experience.
-
I guess you didn't read the text books either.
Darwin is not based on sexual attraction - it is survival of the fittest or theory of natural selection (Ever hear of those before?) I.E. Those critters of a species best adapted to a certain environmental niche will survive to reproduce and pass on the traits that allow their progeny to survive. Lamarck idea is that the inheritance of acquired traits is passed on to that critters offspring. It wasn't until Mendel's work was finanally widely accepted by the scientific community that evolution, as we now understand it, was finally synthesized into what we now are taught - Mendel's works were published in 1865 & 1866 but were not widely accepted until about the turn of the century.
-
Giraffe's necks may, in fact, not have grown long in order for them to reach high into trees. If they developed long legs in order to run fast (and they do run fast) and found that size was an advantage (lions think twice before tackling a giraffe) then they would have needed long necks so that they could reach the ground / water without a lot of trouble and presenting a soft target when kneeling. Needless to say, if you find you are tall enough to reach nice green leaves, you will make use of the ability.
Ignore the slight anthropomorphism in the above - you know what I mean; I am referring to advantageous characteristics etc.
Take nothing for granted that you were told at School!
-
Darwin is not based on sexual attraction
If that comment refers to what I wrote, I did not say anything about sexual attraction, but spoke of sexual selection, which is not the same thing.
On the other hand, some traits are not at all to do with a benefit to the survival of the individual, but wholly about attracting a mate (the peacock's tail is one that comes to mind, as is birdsong).
OK, in both cases you might argue that it is a display of fitness, but an exaggerated display to show that the individual has so much excess fitness that it can even afford to mount conspicuous displays that actually put its life in peril (a little like the risk taking behaviour in many human male adolescents).
-
Darwin based his idea of evolution on sex
That is totally inaccurate - it is only those who, because of subtle advantageous characteristics, survive to produce. Please don't quibble when you make a blanket statement such as this. Darwin was not on about sex in any way shape or form. It was about natural selection. There is a vast difference.
-
Darwin based his idea of evolution on sex
That is totally inaccurate - it is only those who, because of subtle advantageous characteristics, survive to produce. Please don't quibble when you make a blanket statement such as this. Darwin was not on about sex in any way shape or form. It was about natural selection. There is a vast difference.
You might argue a distinction in the case of an asexually reproducing organism, but I don't believe Darwin studied asexual reproducing organisms when developing his theory, and would probably have had trouble explaining how variability would have occurred in an asexually reproducing organism. In fact, in the absence of Mendel's understanding of genetics, it is not clear how Darwin's ideas could have explained asexual evolution, since the whole point about Darwin's ideas was the mixing of the traits of the two surviving parents in order to provide sufficient diversity in the next generation to be able to apply selection to that diversity.
That you have yourself indicated that the key factor is "survive to produce", i.e. to reproduce, which for a sexually reproductive organism, means sexual reproduction.
As I have indicated above, in fact sexual attraction (e.g. the peacock's tail) is also a factor in this, but I was never trying to suggest that Darwin actually regarded sexual attraction the major issue, and it is more recent evolutionists who have more extensively modelled that side of evolution.
-
That is not the argument Darwin made. Sexual attraction had nothing to do with it and was never mentioned in his arguments. I am quite familiar with "On the Origin of Species." This was published in 1859. It was not until 1871 that Darwin addresses how his theory was related to sexual selection. You are just wrong.
-
http://en.wikipedia.org/wiki/The_Origin_of_Species
Darwin used comparison to selective breeding and artificial selection as a means for understanding natural selection. No such connection between selective breeding and natural selection was made by Wallace; he expressed it simply as a basic process of nature and did not think the phenomena were in any way related. On Wallace's own first edition of The Origin of Species, he crossed out every instance of the phrase "natural selection" and replaced with it Spencer's "survival of the fittest."
-
'Best able to find food', 'best able to avoid being eaten', best able to deal with climate change' AND 'best able to reproduce' are all examples of 'fitness'.
If a peacock can get his end away more often by having a big sexy tail then it is a 'fitness' criterion.
Whether or not Darwin included it as an example in his theory is hardly very relevant, is it?
-
If we are talking about how Darwin originally framed his theory, it is.
Artificial selection or selective breeding has nothing to do with sexual attraction. Your quote is about selective breeding and the dispute over natural selection and survival of the fittest. What on God's green earth does this have to do with sexual attraction? Sexual attraction as a means of selection was not even introduced into the thought process until the almost the 20th century!
-
If we are talking about how Darwin originally framed his theory, it is.
Artificial selection or selective breeding has nothing to do with sexual attraction. Your quote is about selective breeding and the dispute over natural selection and survival of the fittest. What on God's green earth does this have to do with sexual attraction? Sexual attraction as a means of selection was not even introduced into the thought process until the almost the 20th century!
But I stated clearly in my earlier reply to you that the term 'sex' in my earlier comment only was ever intended to apply to sexual reproduction, not, I repeat not, to sexual attraction.
Sexual attraction has been an issue in later, post-Darwinian development, but I never regarded it as part of anything that Darwin was considering.
-
'Best able to find food', 'best able to avoid being eaten', best able to deal with climate change' AND 'best able to reproduce' are all examples of 'fitness'.
If a peacock can get his end away more often by having a big sexy tail then it is a 'fitness' criterion.
Whether or not Darwin included it as an example in his theory is hardly very relevant, is it?
The difference is whether one is looking at fitness within the context of an external environment, or fitness with regard to an environment that is itself generated by the species itself, rather than external to the species.
Both are valid issues to consider (particularly when we are talking about highly social species that substantially modify the environment in which individuals within the society survive), but they are different perspectives, and I don't believe that Darwin would have considered social selection as a criteria, although we do now recognise it as a criteria.
-
Darwin based his idea of evolution on sex (i.e. he suggested that evolution went about because males and females selected sexual partners that were beneficial to their children, either through deliberate choice, or because those without the beneficial traits simply did not survive).
"males and females selected sexual partners"- from above
Walks like a duck, squawks like a duck, looks like a duck.
-
Darwin based his idea of evolution on sex (i.e. he suggested that evolution went about because males and females selected sexual partners that were beneficial to their children, either through deliberate choice, or because those without the beneficial traits simply did not survive).
"males and females selected sexual partners"- from above
Walks like a duck, squawks like a duck, looks like a duck.
OK, it was ambiguous, but the second half of that statement included "because those without the beneficial traits simply did not survive" - so what kind of duck is that?
The phrase "deliberate choice" was, I agree, inappropriate for Darwin (although not his successors), but not the second part.
The fact that I used both caveats should have made it clear that the term 'sex' was not being used synonymously with 'sexual attraction', but both caveats taken together did indicate that it could include 'sexual attraction', whereas you are correct that in Darwin's own theory, it should have been explicitly excluded from the definition.
On the other hand, if we are getting picky, your statement:
survival of the fittest or theory of natural selection
The term 'survival of the fittest' originated with Spencer, and was not in the first edition of 'Origins of Species'.
-
Why can't you just say that the statements, even with caveats, were grossly misleading.
-
http://en.wikipedia.org/wiki/Sexual_selection
Sexual selection is the theory proposed by Charles Darwin that states that the frequency of traits can increase or decrease depending on the attractiveness of the bearer.
The theory of sexual selection was first proposed by Charles Darwin in his book The Origin of Species, though it was primarily devoted to natural selection. A later work, The Descent of Man and Selection in Relation to Sex dealt with the subject of sexual selection exhaustively, in part because Darwin felt that natural selection alone was unable to account for certain types of apparently non-competitive adaptations, such as the tail of a male peacock. He once wrote to a colleague that "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!" His work divided sexual selection into two primary categories: male-male competition (which would produce adaptations such as a Bighorn Sheep's horns, which are used primarily in sparring with other males over females), and cases of female choice (which would produce adaptations like beautiful plumage, elaborate songs, and other things related to impressing and attracting).
Darwin's views on sexual selection were opposed strongly by his "co-discoverer" of natural selection, Alfred Russel Wallace, though much of his "debate" with Darwin took place after Darwin's death. Wallace argued that the aspects of it which were male-male competition, while real, were simply forms of natural selection, and that the notion of "female choice" was attributing the ability to judge standards of beauty to animals far too cognitively undeveloped to be capable of aesthetic feeling (such as beetles). Historians have noted that Wallace had previously had his own problem with "female choice": he had been left at the altar by a woman of a higher social class.
Wallace also argued that Darwin too much favored the bright colors of the male peacock as adaptive without realizing that the "drab" peahen's coloration is itself adaptive, as camouflage. Wallace more speculatively argued that the bright colors and long tails of the peacock were not adaptive in any way, and that bright coloration could result from non-adaptive physiological development (for example, the internal organs of animals, not being subject to a visual form of natural selection, come in a wide variety of bright colors). This has been questioned by later scholars as quite a stretch for Wallace, who in this particular instance abandoned his normally strict "adaptationist" agenda in asserting that the highly intricate and developed forms such as a peacock's tail resulted by sheer "physiological processes" that were somehow not at all subjected to adaptation.
Though Darwin considered sexual and natural selection to be two separate processes of equal importance, most of his contemporaries were not convinced, and sexual selection is usually de-emphasized as being a lesser force than, or simply a part of, natural selection.
The sciences of evolutionary psychology, human behavioral ecology, and sociobiology study the influence of sexual selection in humans, though these are often controversial fields. The field of epigenetics is broadly concerned with the competence of adult organisms within a given sexual, social, and ecological niche, which includes the development of mating competences, e.g., by mimicking adult behavior.
So, in retrospect, I was right to include both criteria in my original comment.
-
The difference is whether one is looking at fitness within the context of an external environment, or fitness with regard to an environment that is itself generated by the species itself, rather than external to the species.
Why do you draw a distinction?
As far as the 'selfish gene' is concerned it just needs the best chance of success. Both male and female are 'fitter' if she has the sense to choose a 'fit' male. In this case, 'fitness' represents the ability to produce a fancy display and to be capable of surviving and the ability to recognise that as a way of promoting the female genes.
Good old Richard Dawkins makes this point and I agree with him. (He must be very pleased about that.)
-
The difference is whether one is looking at fitness within the context of an external environment, or fitness with regard to an environment that is itself generated by the species itself, rather than external to the species.
Why do you draw a distinction?
As far as the 'selfish gene' is concerned it just needs the best chance of success. Both male and female are 'fitter' if she has the sense to choose a 'fit' male. In this case, 'fitness' represents the ability to produce a fancy display and to be capable of surviving and the ability to recognise that as a way of promoting the female genes.
Good old Richard Dawkins makes this point and I agree with him. (He must be very pleased about that.)
To Darwin, it would have made a significant difference, because Darwin was not a geneticist, and his book was on the 'Origin of Species', not on the survival of genes.
There is a total difference in perspective between looking at individual genes and looking at species.
To what extent it makes a difference to an individual gene is an interesting question, not least because it leads to questions as to whether, from a genetic perspective one can say that either a multicellular organism, or a species, actually exist. Insofar as one regards a species to exist, then clearly forces external to that species, and acting upon the species, are qualitatively different from forces that are internal within the species; but if one argues that genes do not know about species, then you could argue that it makes no difference to them whether the forces acting upon them are internal to the species or external to the species.
Going back to JimBob's argument of survival of the fittest, the fittest gene is not by any means necessarily the fittest (for survival) of the individual animal - the difference is that a short lived but highly reproductive animal may improve the survival of the species, but will not necessarily benefit the survival of the individual animal, hence sexual advantage is more critical than mere survival (but, again, you can argue that reproduction of the gene is superior even to the sexual advantage of the organism).
-
Referring to the original question (always worth while, occasionally) all that is necessary is to to contrast the idea of Lamarck's idea of passing on some 'learned' characteristic directly to the next generation and the Darwinian idea that effectiveness in survival and reproduction governs the success or failure of some characteristic to turn up in future generations.
Trying to decide exactly what Darwin did or did not think or what he meant by what he wrote is not part of the original brief. And who can tell, in any case?
BTW, Is there any actual evidence to support the Lamarck view, these days?
And, as for Linnaeus, his classification system hangs almost entirely on visible structure. Nowadays there is a possibly 'better' way, based on DNA comparisons. A number of species now find themselves in a very different place in their family tree.
-
Referring to the original question (always worth while, occasionally) all that is necessary is to to contrast the idea of Lamarck's idea of passing on some 'learned' characteristic directly to the next generation and the Darwinian idea that effectiveness in survival and reproduction governs the success or failure of some characteristic to turn up in future generations.
Trying to decide exactly what Darwin did or did not think or what he meant by what he wrote is not part of the original brief. And who can tell, in any case?
BTW, Is there any actual evidence to support the Lamarck view, these days?
No
And, as for Linnaeus, his classification system hangs almost entirely on visible structure. Nowadays there is a possibly 'better' way, based on DNA comparisons. A number of species now find themselves in a very different place in their family tree.
Correct.
It is important to be precise when comparing the original work to the body of the work for some one asking a specific question as this student does. The question asked was to compare Darwin to Lamarck, not what is understood today.
Darwin's full title is "On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life."
From Chapter 4 - Subchapter - Sexual Selection
"Inasmuch as peculiarities often appear under domestication in one sex
and become hereditarily attached to that sex, the same fact probably
occurs under nature, and if so, natural selection will be able to
modify one sex in its functional relations to the other sex, or in
relation to wholly different habits of life in the two sexes, as is
sometimes the case with insects."
"Sexual selection is, therefore, less rigorous
than natural selection."
The section on sexual selection is three paragraphs long and is just a comment, not amplified on until 1871.
"SUMMARY OF CHAPTER.
If during the long course of ages and under varying conditions of
life, organic beings vary at all in the several parts of their
organisation, and I think this cannot be disputed; if there be, owing
to the high geometrical powers of increase of each species, at some
age, season, or year, a severe struggle for life, and this certainly
cannot be disputed; then, considering the infinite complexity of the
relations of all organic beings to each other and to their conditions
of existence, causing an infinite diversity in structure,
constitution, and habits, to be advantageous to them, I think it would
be a most extraordinary fact if no variation ever had occurred useful
to each being's own welfare, in the same way as so many variations
have occurred useful to man. But if variations useful to any organic
being do occur, assuredly individuals thus characterised will have the
best chance of being preserved in the struggle for life; and from the
strong principle of inheritance they will tend to produce offspring
similarly characterised. This principle of preservation, I have
called, for the sake of brevity, Natural Selection. Natural selection,
on the principle of qualities being inherited at corresponding ages,
can modify the egg, seed, or young, as easily as the adult. Amongst
many animals, sexual selection will give its aid to ordinary
selection, by assuring to the most vigorous and best adapted males the
greatest number of offspring. Sexual selection will also give
characters useful to the males alone, in their struggles with other
males." This last "males alone" reflects a very poor understanding of the subject and the whole of the work shows a poor understanding of this subject of sexual selection.
The words "sexual selection" is found only 9 times in the book of some 157,000+ words - It is by no means the foundation of the book and is a secondary subject addressed fully in 1871 by Darwin. It is an afterthought only in "On the Origin of Species By Means of Natural Selection."
Sexual Selection is always secondary to Natural Selection by the environment and is to this day. Studies of Coleoptera in the Amazon Basin come to mind as an example.
-
Referring to the original question (always worth while, occasionally) all that is necessary is to to contrast the idea of Lamarck's idea of passing on some 'learned' characteristic directly to the next generation and the Darwinian idea that effectiveness in survival and reproduction governs the success or failure of some characteristic to turn up in future generations.
Trying to decide exactly what Darwin did or did not think or what he meant by what he wrote is not part of the original brief. And who can tell, in any case?
BTW, Is there any actual evidence to support the Lamarck view, these days?
The trouble is that actually it is no easier to say what Lamarck did or did not think, and the lines between Lamarck and Darwin are not always as clear cut as modern thinking would have us believe. The additional problem with Lamarck is that we (and Darwin) as English speakers have to translate the French of Lamarck, and some have question whether the translation is true to the original intent.
http://en.wikipedia.org/wiki/Lamarckism
Lamarckism or Lamarckian evolution refers to the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as based on heritability of acquired characteristics or "soft inheritance"). It is named for the French biologist Jean-Baptiste Lamarck, who incorporated the action of soft inheritance into his evolutionary theories and is often incorrectly cited as the founder of soft inheritance. It proposed that individual efforts during the lifetime of the organisms were the main mechanism driving species to adaptation, as they supposedly would acquire adaptive changes and pass them on to offspring.
After publication of Charles Darwin's theory of natural selection, the importance of individual efforts in the generation of adaptation was considerably diminished. Later, Mendelian genetics supplanted the notion of inheritance of acquired traits, eventually leading to the development of the modern evolutionary synthesis, and the general abandonment of the Lamarckian theory of evolution in biology. In a wider context, soft inheritance is of use when examining the evolution of cultures and ideas, and is related to the theory of Memetics.
So, at very least, Lamarckism is not the invention of Lamarck, but rather just something he inherited (in the memetic sense).
http://en.wikipedia.org/wiki/Lamarckism#Lamarck.27s_theory
The identification of "Lamarckism" with the inheritance of acquired characteristics is regarded by some as an artifact of the subsequent history of evolutionary thought, repeated in textbooks without analysis. Stephen Jay Gould wrote that late 19th century evolutionists "re-read Lamarck, cast aside the guts of it ... and elevated one aspect of the mechanics - inheritance of acquired characters - to a central focus it never had for Lamarck himself." He argued that "the restriction of "Lamarckism" to this relatively small and non-distinctive corner of Lamarck's thought must be labelled as more than a misnomer, and truly a discredit to the memory of a man and his much more comprehensive system"
http://en.wikipedia.org/wiki/Lamarckism
Darwin's Origin of Species proposed natural selection as the main mechanism for development of species, but did not rule out a variant of Lamarckism as a supplementary mechanism.
-
BTW, Is there any actual evidence to support the Lamarck view, these days?
No
Nobody would dare use the word 'Lararckism' to describe anything in their theory, but there is various ongoing research in what is known as epigenetic inheritance, but as yet this is still not clear what the mechanisms are, or whether you could stretch the term 'Lamarckism' to cover them.
Another interesting argument seems to be that the distinction between the Darwinian model and Lamarckism is only really applicable to multicellular organisms, since it is only in multicellular organisms that you can make a distinction between the germ cells and the body of the organism, and if they are one and the same thing (which they must be for a single celled organism), then a change to the single cell is also a change to the germ cells that define its offspring.
-
Ozze; what level is your assignment aimed at?
I suspect it may be 'School' level, in which case you may be needing a much more concise answer than you have been given so far.
-
let me settle this arguement that seems to have gone on too far.
another_someone is correct.
JimBob is correct EXCEPT in asserting that another_someone is wrong.
Nothing was ever said about sexual attraction, although this wouldn't have even neccesarily made the statements wrong.
Darwinian evolution deals with REPRODUCTIVE FITNESS, this encompases EVERYTHING from the ability to survive, the ablity to attract a mate, the ability to mate, the ability to secure the suvival of one's offspring and MANY more factors.
-
talking of natural selection; I wonder if modern students are evolving a successful characteristic or and unsuccessful characteristic by learning to rely on some of the ravings they can read in these posts. (Mine included).
Are they weeded out in the exam selection process?