How was it proven that Lemarck was wrong?

[Laika]

i would like to pick the brains of a few science enthusiasts.

My understanding is that Lemarck was responsible for the theory of inheritance by acquired traits. In the 19th century it made a certain amount of sense as humans altered species for their own purposes: such as breeding cattle for higher milk and meat yields, fatter chickens that lay more eggs, breeding dogs and pigeons for ascetic qualities, etc.

This contrasted with Gregor Mandell who is responsible for the theory of inheritance of genetic traits (developed from experiments with peas I think).

Fast forward to 2016, and Lemarck is out of favour and Mandell is in favour. Whilst I understand this is to do with discoveries in genetics establishing the mechanism of inheritance I am unclear exactly how lemarkian views were disproven or whether they were simply discarded. Or is this 19th century debate still raging but in a new form?

Can anyone explain that bit for me?

 

[LuisDantas]

I take it you mean Lamarck and Mendel?

I am not well versed in the specifics, but it stands to reason that by now there is way too much observation and experimentation for any doubts about whether there is anything to Lamarckism to remain.

If I am not mistaken, Darwin actually believed in Lamarckism at first. But it turned out to be incompatible with observable facts almost from the get go, once people actually took the trouble to make observations and experimentation.

 

[Laika]

I take it you mean Lamarck and Mendel?

I am not well versed in the specifics, but it stands to reason that by now there is way too much observation and experimentation for any doubts about whether there is anything to Lamarckism to remain.

If I am not mistaken, Darwin actually believed in Lamarckism at first. But it turned out to be incompatible with observable facts almost from the get go, once people actually took the trouble to make observations and experimentation.

Yeah. My spelling is only as good as my memory as I am posting this on my mums iPhone.

It is right that Darwin did accept Lamarck and I believe there are some references to it in the origin of species (I wouldn't know these off hand).

As I said in my OP there are some observations which made Lamarckism views plausible. This may perhaps be a question about how Lamarck's views were superseded by Mandel and what observations were instrumental in doing so.

I may perhaps be confusing the issue as true/false and right/wrong distinctions are not absolutes in science given that information in old theories is incorporated into new ones.

 

[Helvetios]

Gregor Mendel discovered the specific mechanisms of inheritance, and Mendelian genetics is the most basic model for inheritance that we have. Dominant and recessive genes, independent assortment, many general principles are derived from his meticulous experiments and they are the first rules taught in any genetics course. Darwin's research was focused on how traits change; Mendel's focus was on which traits were passed on and how that was done. Mendel didn't actually know which substance was responsible for inheritance, since he lived before the discovery of DNA, but his findings were correct anyway.

Darwin and Lamarck had a different focus than Mendel. Inheritance was a part of their research, but they both proposed models of evolution (not inheritance, but change, although inheritance is a major factor). Lamarckian evolution was the generally accepted model in Darwin's time.

According to Lamarck, if an organism adapts to a changing environment during its lifetime, these changes are passed down to its offspring. A classic example is the giraffe's neck: Lamarck would have proposed that the giraffes stretched their necks more and more to reach the leaves on tree branches, and thus the offspring of these giraffes would have longer necks than their parents. Lamarck also said that body parts that are not used will disappear. For example, humans don't use their little toes for anything anymore, and he proposed that humans would one day be born without them. He believed that evolution proceeds according to a predetermined plan and that the results have already been decided (e.g. evolution's goal for elephants is that they be able to reach the fruit growing on trees, therefore elephants' trunks get longer and longer until that goal is achieved).

Darwinian evolution is quite different, and easily apparent to anyone studying inheritance. Darwin removed the idea of an evolutionary 'goal', and with it the notion that acquired traits can be passed down. If your parent lost one of their legs before they conceived you, that doesn't mean that you would be born without a leg as well. Some traits are encoded in DNA, RNA and preserved in the epigenome; these are passed down. Adaptations that are acquired during the lifetime of the parent, such as increased strength and endurance through exercise, are not inheritable by the offspring. The marriage of Darwinian ideas and genetics is responsible for modern evolutionary theory. Lamarck's ideas were based on false assumptions and are no longer taught, except as part of the history of science.

Lamarck had nothing to do with Mendel, by the way. Mendel was challenging the idea that parents' traits are simply blended into their offspring, and showed that some traits are dominant while others are recessive and hidden. He was not investigating evolution (change). Genetics and evolution are now tied closely together because mutation (changes in DNA) is the raw material that evolution acts upon. They are not the same thing. Inheritance is concerned with how traits are passed on to offspring, while evolution is concerned with how these traits change over time.

 

[beenherebeforeagain]

There was a Soviet biologist--can't recall the name off the top of my head--who was a Lamarckian...he was a high official in the government for many years as I recall, and did many things to revolutionize farming in the USSR, but that also led to many bad decisions as well.

 

[Laika]

Gregor Mendel discovered the specific mechanisms of inheritance, and Mendelian genetics is the most basic model for inheritance that we have. Dominant and recessive genes, independent assortment, many general principles are derived from his meticulous experiments and they are the first rules taught in any genetics course. Darwin's research was focused on how traits change; Mendel's focus was on which traits were passed on and how that was done. Mendel didn't actually know which substance was responsible for inheritance, since he lived before the discovery of DNA, but his findings were correct anyway.

Darwin and Lamarck had a different focus than Mendel. Inheritance was a part of their research, but they both proposed models of evolution (not inheritance, but change, although inheritance is a major factor). Lamarckian evolution was the generally accepted model in Darwin's time.

According to Lamarck, if an organism adapts to a changing environment during its lifetime, these changes are passed down to its offspring. A classic example is the giraffe's neck: Lamarck would have proposed that the giraffes stretched their necks more and more to reach the leaves on tree branches, and thus the offspring of these giraffes would have longer necks than their parents. Lamarck also said that body parts that are not used will disappear. For example, humans don't use their little toes for anything anymore, and he proposed that humans would one day be born without them. He believed that evolution proceeds according to a predetermined plan and that the results have already been decided (e.g. evolution's goal for elephants is that they be able to reach the fruit growing on trees, therefore elephants' trunks get longer and longer until that goal is achieved).

Darwinian evolution is quite different, and easily apparent to anyone studying inheritance. Darwin removed the idea of an evolutionary 'goal', and with it the notion that acquired traits can be passed down. If your parent lost one of their legs before they conceived you, that doesn't mean that you would be born without a leg as well. Some traits are encoded in DNA, RNA and preserved in the epigenome; these are passed down. Adaptations that are acquired during the lifetime of the parent, such as increased strength and endurance through exercise, are not inheritable by the offspring. The marriage of Darwinian ideas and genetics is responsible for modern evolutionary theory. Lamarck's ideas were based on false assumptions and are no longer taught, except as part of the history of science.

Lamarck had nothing to do with Mendel, by the way. Mendel was challenging the idea that parents' traits are simply blended into their offspring, and showed that some traits are dominant while others are recessive and hidden. He was not investigating evolution (change). Genetics and evolution are now tied closely together because mutation (changes in DNA) is the raw material that evolution acts upon. They are not the same thing. Inheritance is concerned with how traits are passed on to offspring, while evolution is concerned with how these traits change over time.

Many thanks. I will probably re-read that a few times as its so well written. It is much appreciated.

There was a Soviet biologist--can't recall the name off the top of my head--who was a Lamarckian...he was a high official in the government for many years as I recall, and did many things to revolutionize farming in the USSR, but that also led to many bad decisions as well.

It's Lysenko. He got official endorsement from Stalin in the 1930's and his thories dominated soviet biology until the 60's. It was the original context I was thinking about this in as neolamarckian theories fitted into materialist philosophy of Marxism. The political dimension was that genetics was banned because when applied to society it can lead to assumption of innate inequalities (mandellian genetics was used as part of nazi ideology but in linking racial and moral characteristic) whereas Lamarck doesn't have that issue because traits can change and "environment" takes precedence.

I decided to dump it though and go with Lamarck because it was be less about politics and more about the philosophical and scientific reasons Lamarck was wrong. Just simplified things a bit.

 

[Helvetios]

There was a Soviet biologist--can't recall the name off the top of my head--who was a Lamarckian...he was a high official in the government for many years as I recall, and did many things to revolutionize farming in the USSR, but that also led to many bad decisions as well.

That would be Trofim Lysenko, who claimed his ideas were distinct from Lamarckism despite sharing many similarities. He did not believe that DNA existed; instead, he believed that the entire body of an organism was capable of passing down information to the next generation (and yes, this includes acquired traits during the individual's lifetime, the same claim that Lamarck supported.) Like Lamarck, he also believed in evolutionary purpose: according to his beliefs, weaker plants died in order to nourish stronger ones - purposefully - and not because they lacked sunlight or water. He had a peculiar focus on selecting and supporting the strong, and discarding the weak, which isn't exactly what inheritance and evolution are about.

Lysenko's ideas went against Mendel's and Darwin's work, as well as all the new information that biologists were learning at the time. His hypotheses' inability to fully explain inheritance led other scientists to accuse him of pseudoscience. At the same time, his work was well-known in the USSR. Not only did Stalin praise his shoddy advances in agriculture, eventually all scientific criticism of his ideas was made illegal. I'd say he is an important factor in the backwardness of the USSR, although his influence was only made possible because the government saw parallels between his ideas and the New Soviet Man, and because he was born from a poor family with no connection to academia (fitting with Stalin's affection for the proletariat).

 

[Ouroboros]

Fast forward to 2016, and Lemarck is out of favour and Mandell is in favour. Whilst I understand this is to do with discoveries in genetics establishing the mechanism of inheritance I am unclear exactly how lemarkian views were disproven or whether they were simply discarded. Or is this 19th century debate still raging but in a new form?

The debate is over... kind'a, but a semi-lamarckian view has been introduced in epigenetics. Diet and environment for the parents can affect the offspring. It's not just DNA that is inherited.

Anyway, when the Russian revolution happened, Soviet adopted Lamarckian evolution while the West adopted the Mendelian. I'm not sure the reasons, but I suspect that some western scientists already had seen that inheritable traits can't be "trained". The reason Soviet didn't pick up the Mendelian and choose Lamarck, was because west picked Mendel. Mendelian darwinism was "obviously" driven by the capitalist west. I did read some articles with quotes from that time, but I can't even recall the quotes anymore. Too long ago.

So... anywho #2. Soviet decided to go Lamarck, which led to experiments like planting potato in the winter to "train" them to withstand cold... and it didn't work, and millions starved to death. While west, experimented to why and how the Mendelian traits were inherited, and discovered DNA. And the war between the two theories was over.

But... back to epigenetics, the DNA seems to not be the only carrier of traits. Not sure I can explain it all, but apparently obesity and medical sideeffects can be inherited, or something like that.

This is how I understand it happened after reading some books and articles some years ago, but don't quote me on these things. It's just my impression of these things.

 

[beenherebeforeagain]

The debate is over... kind'a, but a semi-lamarckian view has been introduced in epigenetics. Diet and environment for the parents can affect the offspring. It's not just DNA that is inherited.

Anyway, when the Russian revolution happened, Soviet adopted Lamarckian evolution while the West adopted the Mendelian. I'm not sure the reasons, but I suspect that some western scientists already had seen that inheritable traits can't be "trained". The reason Soviet didn't pick up the Mendelian and choose Lamarck, was because west picked Mendel. Mendelian darwinism was "obviously" driven by the capitalist west. I did read some articles with quotes from that time, but I can't even recall the quotes anymore. Too long ago.

So... anywho #2. Soviet decided to go Lamarck, which led to experiments like planting potato in the winter to "train" them to withstand cold... and it didn't work, and millions starved to death. While west, experimented to why and how the Mendelian traits were inherited, and discovered DNA. And the war between the two theories was over.

But... back to epigenetics, the DNA seems to not be the only carrier of traits. Not sure I can explain it all, but apparently obesity and medical sideeffects can be inherited, or something like that.

This is how I understand it happened after reading some books and articles some years ago, but don't quote me on these things. It's just my impression of these things.

The modern epigenetics part is just starting to take off--starvation, malnutrition, exposure to chemicals, radiation, even illnesses and parasites, (and apparently, not just negative things, either) can affect not just offspring, but the next several generations in at least some cases. At least some of these exposures/experiences affect the way that genes are expressed in the following generations. And that doesn't even get into the effects that our microfauna both external and internal can have on us and later generations. There was some recent study that suggests that cities have different microbiomes that literally change the way people experience the environment.

 

[beenherebeforeagain]

That would be Trofim Lysenko, who claimed his ideas were distinct from Lamarckism despite sharing many similarities. He did not believe that DNA existed; instead, he believed that the entire body of an organism was capable of passing down information to the next generation (and yes, this includes acquired traits during the individual's lifetime, the same claim that Lamarck supported.) Like Lamarck, he also believed in evolutionary purpose: according to his beliefs, weaker plants died in order to nourish stronger ones - purposefully - and not because they lacked sunlight or water. He had a peculiar focus on selecting and supporting the strong, and discarding the weak, which isn't exactly what inheritance and evolution are about.

Lysenko's ideas went against Mendel's and Darwin's work, as well as all the new information that biologists were learning at the time. His hypotheses' inability to fully explain inheritance led other scientists to accuse him of pseudoscience. At the same time, his work was well-known in the USSR. Not only did Stalin praise his shoddy advances in agriculture, eventually all scientific criticism of his ideas was made illegal. I'd say he is an important factor in the backwardness of the USSR, although his influence was only made possible because the government saw parallels between his ideas and the New Soviet Man, and because he was born from a poor family with no connection to academia (fitting with Stalin's affection for the proletariat).

Yes, Lysenko (both you and Laika). Used to know quite a bit about his beliefs and what happened; my memory is really getting spotty...can't answer the "Soviet Scientists for $500, Alex" questions any more...

 

[Ouroboros]

The modern epigenetics part is just starting to take off--starvation, malnutrition, exposure to chemicals, radiation, even illnesses and parasites, (and apparently, not just negative things, either) can affect not just offspring, but the next several generations in at least some cases. At least some of these exposures/experiences affect the way that genes are expressed in the following generations. And that doesn't even get into the effects that our microfauna both external and internal can have on us and later generations. There was some recent study that suggests that cities have different microbiomes that literally change the way people experience the environment.

Good points, especially about microbiomes.

I remember reading years ago that many of our fundamental gut flora comes from our parents, by cuddling and kissing on the cheek. Basically, close contact, care, nurturing, etc is part of a healthy gut, which also can be related to issues like allergies and other illnesses later in life.