Posted: Feb 16, 2012 3:18 pm
Inheritance of Acquired Characteristics
Intro
The inheritance of acquired characteristics, or Lamarckism, was a leading hypothesis explaining the passing on of physical traits from individuals into its offspring. This hypothesis was popular since Ancient Greece, was held to be true by Aristotle and Hippocrates, and was believed to be biological fact up until Charles Darwin did his research and developed his Hypothesis of Natural Selection. In 1809, biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck, today known as Lamarck, developed his hypothesis which clarified and defined Lamarckism. [1]
Lamarck having studied invertebrates and botany for most of his life was intrigued by the vast diversity of life around him. In fact, Lamarck is a forerunner to defining modern evolutionary theory and although wrong in his hypothesis would be a major influence on Darwin and his research into evolutionary mechanisms. [2]
What the Hypothesis Stated
Lamarck’s hypothesis in his book, Zoological Philosophy, held several key points or “laws” explaining the reasoning how physical traits were passed from parent into offspring.
“[First Law] In every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears.
[Second Law] All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which their race has long been placed, and hence through the influence of the predominant use or permanent disuse of any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired modifications are common to both sexes, or at least to the individuals which produce the young.”
These laws would be simplified in textbooks as 1) use and disuse and the 2) inheritance of acquired traits.
Lamarck concluded that nature was the designer of animals, plants and their diversity. He also concluded, in accordance with his laws, that it was the environment which caused species to inherit traits. Lamarck in his Zoological Philosophy writes, “Nature (or her Author) in creating animals, foresaw all the possible kinds of environment in which they would have to live, and endowed each species with a fixed organization and with a definite and invariable shape, which compel each species to live in the places and climates where we actually find them, and there to maintain the habits which we know in them” In simpler words, Lamarck believed that all creatures’ traits were best suited to a specific environment from “creation” and that when changes to the environment occurred; the individual animals in the species would adapt physical traits to allow it to survive.
Lamarck also had his individual conclusion which stated that there was an increasing complexity occurring in nature with regards to life, “Nature has produced all the species of animals in succession, beginning with the most imperfect or simplest, and ending her work with the most perfect, so as to create a gradually increasing complexity in their organization; these animals have spread at large throughout all the habitable regions of the globe, and every species has derived from its environment the habits that we find in it and the structural modifications which observation shows us” [3]
An example of Lamarckism would be the giraffe stretching its neck, thus strengthening the muscles around its neck, thus using the organ which increases its function. This giraffe would pass on its acquired, stronger muscles into its offspring and that giraffe would stretch its neck until you had a modern giraffe. This example follows both of Lamarck’s laws of Use and Disuse and the Inheritance of Acquired Traits. However, in modern biological science we know this example is wrong.
Falsification of the Hypothesis
Unfortunately for Lamarck, immediately after his death, two rising scientists almost shattered the hypothesis of Lamarckism. These scientists were the Austrian friar Gregor Mendel and the British naturalist Charles Darwin.
• Gregor Mendel
Gregor Mendel is well known for his experiments with pea plants, among other species, and recording his observations of inheritable traits among the species. Mendel cross-bred a white flowered pea plant with a purple flowered pea plant expecting the outcome to result in the, at the time, accepted hypothesis of blended inheritance; Mendel expected a light purple flower. Instead Mendel was given a purple flower offspring. Mendel discovered that on a consistent basis a white flowered plant bred with a white flowered plant would yield a white flowered plant, a purple flowered plant bred with a purple flowered plant would yield a purple flowered plant, and a purple flowered plant bred with a white flowered plant would yield a purple flowered plant. To continue his experimentation, Mendel bred the offspring purple flowered plants and was again astonished. Instead of getting a consistent purple flower, it would yield a 3:1 ratio purple flowered/white flowered plant. Meaning out of every four plants there was a likelihood one would be white. These experiments not only on the flower but on the pea shape and pea colour and other traits of the plant would lead Mendel to create his inheritance hypothesis.
This hypothesis had three main points. The first was inheritance of traits is factored by “units” (we call them genes, but Mendel did not know they existed), the second was one unit for each trait is inherited from each parent, and the third was a trait may not show in the individual but can show up in a later generation. Today Mendel’s experiments can be summarized by two principles (or laws): The principle of segregation and the principle of independent assortment. [4]
Wikipedia says that the law of segregation states that, “Every individual possesses a pair of alleles (assuming diploidy) for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring. The offspring then receives its own pair of alleles for that trait. Whichever of the two alleles in the offspring is dominant determines how the offspring expresses that trait (e.g. the color of a plant, the color of an animal's fur, the color of a person's eyes).”
Relating this back to Lamarckism, Lamarck argued that it was the environment which caused the individual species to adapt. Mendel discovered this was not the case, but rather the units or genes which contain the trait are responsible for the trait to show. Using the giraffe example, Mendel would have argued there was a unit which contained a trait for the long neck of the giraffe which would have been passed from parent to offspring until the long neck unit was a dominant trait. Remember Mendel did not have knowledge of DNA and unfortunately did not have communications with his contemporary, Charles Darwin.
Wikipedia also explains that the law of independent assortment states that, “Separate genes for separate traits are passed independently of one another from parents to offspring. That is, the biological selection of a particular gene in the gene pair for one trait to be passed to the offspring has nothing to do with the selection of the gene for any other trait.” This is not always the case, because modern genetics show that some genes are linked, but for the purpose of inheritance this is generally the rule.
So how does this relate to Lamarckism? Well Lamarck’s second law was that the acquired traits of the parent would pass down into the offspring. Again Mendel’s experiments show this is not the case. If Mendel were to cut off the petals of the parent flower, the offspring would not be born without petals. This flaw in Lamarckism is shown in the classic example of a Doberman Pinscher. A Doberman traditionally would have its ears cropped and its tail docked. But, its offspring would have normal, uncropped ears and a normal, undocked tail, and would grow into adult with those traits.
Not only does this show that Lamarck’s inheritability law was wrong, it shows that there has to be something beyond the physical outwardly traits that caused inheritability. Mendel’s experiments and hypothesis show that there is a “unit” which contains information of a specific, individual trait and Mendel’s experiments also show how these traits get passed and the ratio they occur within generations.
• Charles Darwin
The famous Charles Darwin is largely responsible for the coining of two modern evolutionary terms. The first is natural selection and the second common descent. Both of these refute Lamarck’s hypothesis of Inheritance of Acquired Characteristics.
Darwin, while studying at the Galapagos Islands, noticed small variations of traits within the finches on each island. Each finch seemed to be suited for the habitat and local environment it dwelled in. Lamarckism would hold that the finch adapted to the environment and passed on its trait to its offspring. Example, a finch that had a sharper beak for drilling holes into the bark obtained that sharper beak by some means, either repeated attempts to get food, or it sharpened it, and that acquired beak was passed on to its offspring whom would obtain a better beak for getting food.
Darwin would disagree. After visiting renowned ornithologist John Gould, Darwin realized that each individual species of finch are so related it is as if small changes had occurred within an original species to create the diversity. He would go on to form his hypothesis of natural selection. From Origen of Species:
“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.” [6]
In short, Darwin believed that species acquired traits which would best suit that species more and the likelihood of that species surviving would increase. In layman’s terms this is survival of the fittest. Now Darwin knew nothing about genes, although he guessed there had to be something that triggered these changes within species. Lamarck’s idea of inheritance of physical traits was unsatisfactory for Darwin at this time.
Furthermore, Darwin did not believe each species was created by nature as fitted to its environment and would adapt, but rather believed that each species shares a common descent with another species. Darwin was so bold as to suggest all life on the planet was connected through a tree of ancestry. Of course with modern genetics we know this to be true.
To summarize, Darwin proposed two alternatives to Lamarckism. The first is natural selection as the means of inheritability and diversity of species. Instead of use and disuse, it was the possession of a stronger trait which increased chances of survival and subsequent healthy breeding. The second was that all life can be traced in an ancestry.
Conclusion
Today we have advanced, clarified and combined both Mendel’s hypothesis and Darwin’s hypotheses and filled the gaps with knowledge of DNA and genetics. Through stochastic mutations, which occur during DNA replication, specific proteins are changed and result in either a change in the trait or nothing life changing. If the result is a change than the change is either beneficial or harmful for the individual; either way selection will affect the organism. With our knowledge of various genomes and the gems of the fossil record, Darwin’s hypothesis of common descent was shown to be fact and that all animals, plants, fungi, protozoa, and bacteria share a biological relationship with each other. In short, the two premises of Lamarckism are refuted with today’s understanding of how species acquire traits.
Why is this important?
Several main reasons why the refuting of Lamarck’s claims are important:
1) Modern Biology would not be as conclusive.
2) Modern Germ Theory and subsequently medicine would not be as advanced
3) Many intellectually dishonest apologetics still cling to a Lamarckism-esque philosophy when debating modern evolution.
Modern biology includes a vast amount of individual subjects, but because of our knowledge of evolutionary theory, scientists know that everything in biology is connected at the molecular level and is very consistent science.
Without the knowledge of how traits are acquired, germs, bacteria, and viruses could arguably be more potent since pharmaceutics would have a weak basis of inheritance to counter the pathogen.
Creationists oftentimes claim evolution occurred in small stages of adaption (microevolution) but that God (or Nature) created the species as they were and had just adapted. Although this is not exactly what Lamarck believed, Creationists tend to think this is what the science supports.
Although Lamarckism is an insufficient explanation for the inheritance of traits in Eukaryotic life, today scientists have discovered that RNA prokaryotes can acquire traits in a fashion similar to what Lamarck proposed. In fact, epigenetics studies this. [7]
Index
1. http://en.wikipedia.org/wiki/Inheritanc ... cteristics
2. http://www.ucmp.berkeley.edu/history/lamarck.html
3. Zoological Philosophy: An Exposition With Regard to the Natural History of Animals by Jean-Baptiste Lamarck. p. 113, 126 (1984).
4. http://www.bioinformatics.nl/webportal/ ... linfo.html
5.http://en.wikipedia.org/wiki/Mendelian_inheritance
6. On the Origin of Species by Charles Darwin. p. 80-81. (2011).
7. http://www.sciencedaily.com/releases/20 ... 102713.htm
Intro
The inheritance of acquired characteristics, or Lamarckism, was a leading hypothesis explaining the passing on of physical traits from individuals into its offspring. This hypothesis was popular since Ancient Greece, was held to be true by Aristotle and Hippocrates, and was believed to be biological fact up until Charles Darwin did his research and developed his Hypothesis of Natural Selection. In 1809, biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck, today known as Lamarck, developed his hypothesis which clarified and defined Lamarckism. [1]
Lamarck having studied invertebrates and botany for most of his life was intrigued by the vast diversity of life around him. In fact, Lamarck is a forerunner to defining modern evolutionary theory and although wrong in his hypothesis would be a major influence on Darwin and his research into evolutionary mechanisms. [2]
What the Hypothesis Stated
Lamarck’s hypothesis in his book, Zoological Philosophy, held several key points or “laws” explaining the reasoning how physical traits were passed from parent into offspring.
“[First Law] In every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears.
[Second Law] All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which their race has long been placed, and hence through the influence of the predominant use or permanent disuse of any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired modifications are common to both sexes, or at least to the individuals which produce the young.”
These laws would be simplified in textbooks as 1) use and disuse and the 2) inheritance of acquired traits.
Lamarck concluded that nature was the designer of animals, plants and their diversity. He also concluded, in accordance with his laws, that it was the environment which caused species to inherit traits. Lamarck in his Zoological Philosophy writes, “Nature (or her Author) in creating animals, foresaw all the possible kinds of environment in which they would have to live, and endowed each species with a fixed organization and with a definite and invariable shape, which compel each species to live in the places and climates where we actually find them, and there to maintain the habits which we know in them” In simpler words, Lamarck believed that all creatures’ traits were best suited to a specific environment from “creation” and that when changes to the environment occurred; the individual animals in the species would adapt physical traits to allow it to survive.
Lamarck also had his individual conclusion which stated that there was an increasing complexity occurring in nature with regards to life, “Nature has produced all the species of animals in succession, beginning with the most imperfect or simplest, and ending her work with the most perfect, so as to create a gradually increasing complexity in their organization; these animals have spread at large throughout all the habitable regions of the globe, and every species has derived from its environment the habits that we find in it and the structural modifications which observation shows us” [3]
An example of Lamarckism would be the giraffe stretching its neck, thus strengthening the muscles around its neck, thus using the organ which increases its function. This giraffe would pass on its acquired, stronger muscles into its offspring and that giraffe would stretch its neck until you had a modern giraffe. This example follows both of Lamarck’s laws of Use and Disuse and the Inheritance of Acquired Traits. However, in modern biological science we know this example is wrong.
Falsification of the Hypothesis
Unfortunately for Lamarck, immediately after his death, two rising scientists almost shattered the hypothesis of Lamarckism. These scientists were the Austrian friar Gregor Mendel and the British naturalist Charles Darwin.
• Gregor Mendel
Gregor Mendel is well known for his experiments with pea plants, among other species, and recording his observations of inheritable traits among the species. Mendel cross-bred a white flowered pea plant with a purple flowered pea plant expecting the outcome to result in the, at the time, accepted hypothesis of blended inheritance; Mendel expected a light purple flower. Instead Mendel was given a purple flower offspring. Mendel discovered that on a consistent basis a white flowered plant bred with a white flowered plant would yield a white flowered plant, a purple flowered plant bred with a purple flowered plant would yield a purple flowered plant, and a purple flowered plant bred with a white flowered plant would yield a purple flowered plant. To continue his experimentation, Mendel bred the offspring purple flowered plants and was again astonished. Instead of getting a consistent purple flower, it would yield a 3:1 ratio purple flowered/white flowered plant. Meaning out of every four plants there was a likelihood one would be white. These experiments not only on the flower but on the pea shape and pea colour and other traits of the plant would lead Mendel to create his inheritance hypothesis.
This hypothesis had three main points. The first was inheritance of traits is factored by “units” (we call them genes, but Mendel did not know they existed), the second was one unit for each trait is inherited from each parent, and the third was a trait may not show in the individual but can show up in a later generation. Today Mendel’s experiments can be summarized by two principles (or laws): The principle of segregation and the principle of independent assortment. [4]
Wikipedia says that the law of segregation states that, “Every individual possesses a pair of alleles (assuming diploidy) for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring. The offspring then receives its own pair of alleles for that trait. Whichever of the two alleles in the offspring is dominant determines how the offspring expresses that trait (e.g. the color of a plant, the color of an animal's fur, the color of a person's eyes).”
Relating this back to Lamarckism, Lamarck argued that it was the environment which caused the individual species to adapt. Mendel discovered this was not the case, but rather the units or genes which contain the trait are responsible for the trait to show. Using the giraffe example, Mendel would have argued there was a unit which contained a trait for the long neck of the giraffe which would have been passed from parent to offspring until the long neck unit was a dominant trait. Remember Mendel did not have knowledge of DNA and unfortunately did not have communications with his contemporary, Charles Darwin.
Wikipedia also explains that the law of independent assortment states that, “Separate genes for separate traits are passed independently of one another from parents to offspring. That is, the biological selection of a particular gene in the gene pair for one trait to be passed to the offspring has nothing to do with the selection of the gene for any other trait.” This is not always the case, because modern genetics show that some genes are linked, but for the purpose of inheritance this is generally the rule.
So how does this relate to Lamarckism? Well Lamarck’s second law was that the acquired traits of the parent would pass down into the offspring. Again Mendel’s experiments show this is not the case. If Mendel were to cut off the petals of the parent flower, the offspring would not be born without petals. This flaw in Lamarckism is shown in the classic example of a Doberman Pinscher. A Doberman traditionally would have its ears cropped and its tail docked. But, its offspring would have normal, uncropped ears and a normal, undocked tail, and would grow into adult with those traits.
Not only does this show that Lamarck’s inheritability law was wrong, it shows that there has to be something beyond the physical outwardly traits that caused inheritability. Mendel’s experiments and hypothesis show that there is a “unit” which contains information of a specific, individual trait and Mendel’s experiments also show how these traits get passed and the ratio they occur within generations.
• Charles Darwin
The famous Charles Darwin is largely responsible for the coining of two modern evolutionary terms. The first is natural selection and the second common descent. Both of these refute Lamarck’s hypothesis of Inheritance of Acquired Characteristics.
Darwin, while studying at the Galapagos Islands, noticed small variations of traits within the finches on each island. Each finch seemed to be suited for the habitat and local environment it dwelled in. Lamarckism would hold that the finch adapted to the environment and passed on its trait to its offspring. Example, a finch that had a sharper beak for drilling holes into the bark obtained that sharper beak by some means, either repeated attempts to get food, or it sharpened it, and that acquired beak was passed on to its offspring whom would obtain a better beak for getting food.
Darwin would disagree. After visiting renowned ornithologist John Gould, Darwin realized that each individual species of finch are so related it is as if small changes had occurred within an original species to create the diversity. He would go on to form his hypothesis of natural selection. From Origen of Species:
“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.” [6]
In short, Darwin believed that species acquired traits which would best suit that species more and the likelihood of that species surviving would increase. In layman’s terms this is survival of the fittest. Now Darwin knew nothing about genes, although he guessed there had to be something that triggered these changes within species. Lamarck’s idea of inheritance of physical traits was unsatisfactory for Darwin at this time.
Furthermore, Darwin did not believe each species was created by nature as fitted to its environment and would adapt, but rather believed that each species shares a common descent with another species. Darwin was so bold as to suggest all life on the planet was connected through a tree of ancestry. Of course with modern genetics we know this to be true.
To summarize, Darwin proposed two alternatives to Lamarckism. The first is natural selection as the means of inheritability and diversity of species. Instead of use and disuse, it was the possession of a stronger trait which increased chances of survival and subsequent healthy breeding. The second was that all life can be traced in an ancestry.
Conclusion
Today we have advanced, clarified and combined both Mendel’s hypothesis and Darwin’s hypotheses and filled the gaps with knowledge of DNA and genetics. Through stochastic mutations, which occur during DNA replication, specific proteins are changed and result in either a change in the trait or nothing life changing. If the result is a change than the change is either beneficial or harmful for the individual; either way selection will affect the organism. With our knowledge of various genomes and the gems of the fossil record, Darwin’s hypothesis of common descent was shown to be fact and that all animals, plants, fungi, protozoa, and bacteria share a biological relationship with each other. In short, the two premises of Lamarckism are refuted with today’s understanding of how species acquire traits.
Why is this important?
Several main reasons why the refuting of Lamarck’s claims are important:
1) Modern Biology would not be as conclusive.
2) Modern Germ Theory and subsequently medicine would not be as advanced
3) Many intellectually dishonest apologetics still cling to a Lamarckism-esque philosophy when debating modern evolution.
Modern biology includes a vast amount of individual subjects, but because of our knowledge of evolutionary theory, scientists know that everything in biology is connected at the molecular level and is very consistent science.
Without the knowledge of how traits are acquired, germs, bacteria, and viruses could arguably be more potent since pharmaceutics would have a weak basis of inheritance to counter the pathogen.
Creationists oftentimes claim evolution occurred in small stages of adaption (microevolution) but that God (or Nature) created the species as they were and had just adapted. Although this is not exactly what Lamarck believed, Creationists tend to think this is what the science supports.
Although Lamarckism is an insufficient explanation for the inheritance of traits in Eukaryotic life, today scientists have discovered that RNA prokaryotes can acquire traits in a fashion similar to what Lamarck proposed. In fact, epigenetics studies this. [7]
Index
1. http://en.wikipedia.org/wiki/Inheritanc ... cteristics
2. http://www.ucmp.berkeley.edu/history/lamarck.html
3. Zoological Philosophy: An Exposition With Regard to the Natural History of Animals by Jean-Baptiste Lamarck. p. 113, 126 (1984).
4. http://www.bioinformatics.nl/webportal/ ... linfo.html
5.http://en.wikipedia.org/wiki/Mendelian_inheritance
6. On the Origin of Species by Charles Darwin. p. 80-81. (2011).
7. http://www.sciencedaily.com/releases/20 ... 102713.htm