Lamarckism and Darwinism
Marco Parigi has posted this comment in response to my Brecht-Zitate post. It seems to me that is does not really belong there, so I put it here with the hope that it might initiate an interesting discussion on Lamarckism and Darwinism.
“Arguments for modern specific experiments for Lamarckism
I have been reading The Panda’s Thumb and there is a nice chapter devoted to the discussion of Lamarckism. Essentially the tenets of ‘Lamarckism’ is that evolution can be ‘directed’ by environmental factors, rather than by undirected genetic variation being winnowed out by death or lower reproduction rates of fellow individuals of the species allowing the remaining individuals to pass on genes appropriate to the environmental factors. Lamarckism has been rejected by biologists because ‘Darwinism’ explains all facets of evolution satisfactorily, and no direct evidence of Lamarckism has been discovered, as well as the fact that particular examples (giraffe necks etc.) oft quoted have been discredited as being both explainable by darwinism and having no measurable direct evidence of directed genetic change.
A new approach would be to look at it from a completely different angle as follows. If Lamarckism is a force in evolution, what are the best genetic strategies to follow given a pre-reproductive youth to experiment on what genes are useful and which not. The issue to me is that genes would have to predict what future environments will require. Genetic variation would hedge its bets on an environmental change being a temporary or permanent one. I would suggest that modern controlled experiments on a range of different animals over a large number of generations would demonstrate it. Essentially, almost no experiments have been done since the 1920’s and 1930’s. With a greater understanding of the complex role of RNA, more nuanced experiments, I believe would find a subtle but pervasive pathway for some direct/accelerated forms of evolution.
Neither the rat/maze learning experiments and antenna/amputation/regrowth experiments have natural environmental analogies, making them less explanatory than they appear. Direct adaptation would only happen where similar changes in environment had happened before in the distant ancestral history of the animal/plant in question. After all, the specific Lamarckian adaptation itself would have to evolve to suit probable dramatic shifts in environment (ie. selection pressures on species that had no Lamarckian adaptation vs species that did)
One particular experiment would be subjecting specimens to permanent darkness. It is a well known evolutionary theme that vision in a large range of beasts becomes impaired when adapted to permanent darkness. It also has reasonably common natural analogy where animals adapted to light have close relatives adapted to dark with common ancestry. Adaptation to permanently, cold, wet, hot or dry are similarly common natural events that lab experiments could weed out direct vs undirected variation.”
Just seven points which may be relevant for a discussion: 1) Darwin himself believed to a degree in a Lamarckian explanation of evolution, this explanation was finally discarded as the result of the theories of August Weismann; 2) The definition of Lamarckism above is somewhat ambiguous (”Essentially the tenets of ‘Lamarckism’ is that evolution can be ‘directed’ by environmental factors”; it is fairly obvious that evolution is to some degree “directed”, the important point is that acquired characters are passed on to the offspring); 3) Darwinism, as usually interpreted today, in my opinion puts too much emphasis on the importance of competition, particularly interspecific competition. Hence, it would be wise to contrast “intelligent design” with the theory of evolution and not with Darwinism; 4) Both Darwinism and Lamarckism have been misused by politicians, the former to justify eugenic and racist politics, the latter to justify suppression of scientific research because it supposedly led to racist conclusions; 5) Mutations may be constrained by their genetic environment, i.e. they are not entirely random, but this is no evidence for Lamarckism; 6) Reports have been published from time to time claiming evidence for the inheritance of acquired characters (one a number of years ago by an Australian microbiologist); I have not kept track of these reports and how valid they were; 7) Lamarckian ideas of “soft” evolution may still be useful in theories of cultural evolution such as memetics.
January 16th, 2008 at 1:42 pm
The definition of Lamarckism above is somewhat ambiguous …. the important point is that acquired characters are passed on to the offspring
I would like to analyse this from a thought experiment basis rather than a philosophical or search for proof/disproof basis. The thought experiment would go somethng as follows - If Lamarckism (as defined by the important point above) is possible, then would this be of critical adaptive advantage? This hinges on whether experiences within a lifetime suitably predict conditions for the offspring of well into the future. If there are *definitive* environmental signals of a long-term change in local habitat, then Lamarckism would be an advantage to species which develop a trigger for generating a portion of offspring with suitable genetic variance in a particular direction, set off by that signal. Since the future is never 100% predictable, a good strategy would be various mutations on the offspring, all of which have a good chance of surviving, and giving almost certainty that some will be ideally mutated to the new environment. Thus none of the mutations would be “Random” in the conventional sense, but environmental factors would direct that a certain percentage of offspring would have no mutations, while another percentage would have mutations that would be dominant if the habitat change happens to be longer-term (multi-generational).
If the answer is “Yes” this type of Lamarckism is almost certainly possible, and almost certainly gives critical adaptive advantage, one must assumes it exists in this form. One must then only devise experiments which seperate out the genetic variation due to environmental factors from random genetic variation you would see in ultra-stable environments, and find whether there is a direct connection.
January 16th, 2008 at 3:06 pm
“If Lamarckism (as defined by the important point above) is possible, then would this be of critical adaptive advantage?”
No doubt that this would have an enormous adaptive advantage, but not everything that has an advantage is possible. The critical point is whether a genetic mechanism in the Lamarckian sense is possible, and only experiments can show this.
“Thus none of the mutations would be “Random†in the conventional sense, but environmental factors would direct that a certain percentage of offspring would have no mutations, while another percentage would have mutations that would be dominant if the habitat change happens to be longer-term (multi-generational).”
One can imagine situations where past selection (in the conventional sense) has established a mechanism which leads to relatively fast evolutionary changes as an adaption to “anticipated” long-term changes indicated by certain environmental signals. This is not Lamarckism, but simply a “classical” adaptation to recurrent environmental changes.
January 17th, 2008 at 2:32 pm
The critical point is whether a genetic mechanism in the Lamarckian sense is possible, and only experiments can show this.
Recent experiments with RNA referenced in http://marcoparigi.blogspot.com/2007/06/lamarckism-returns.html do demonstrate the possibility. More experiments may determine more exactly what on earth RNA is doing in this regard. I think that this critical point has just recently been demonstrated to my satisfaction.
This is not Lamarckism, but simply a “classical†adaptation to recurrent environmental changes.
I see Lamarckism as a *Shortcut* mechanism that avoids completely mutations that say switch off all genes associated with eyes, unless a parent say falls into a cave. Or similarly for a frog in a very wet environment, genes that help in a very wet environment will very faithfully passed down, unless the watercourse changes and they become drier. Lamarckian shortcuts will always win over genetic mutations unrelated to environmental signals. This, of course will be found with other shortcuts, such as more general mutations when under stress, choosing mates with the right characteristics, and a reduction in population as in classical selection processes.
…
January 17th, 2008 at 3:24 pm
Thanks for the link to the references, which I have not read yet. In the meantime the following example of “vernalization”, which seems to be very relevant and has (mistakenly) been used as evidence for Lamarckism.
Vernalization is found in many temperate plants including important crops. It is the acquisition of the ability to flower in spring by exposure to the winter cold. Many species (such as winter cereals) cannot flower without such exposure; it results in seed production at the most favourable time, i.e. after winter in spring, although additional environmental “signals” may be required for “selecting” the optimal time.
Obviously, the ability to be vernalized has a genetic basis, but - in the Soviet Union under Stalin until Chruchtchev - it was claimed that the “state” of vernalization could be inherited (i.e., it was claimed that a character acquired during the vernalization process was inherited: Lysenko). In other words, it was thought that the offspring of a vernalized plants did not require renewed vernalization to flower in spring. No evidence for this - to my knowledge - has been provided to date.
January 17th, 2008 at 5:02 pm
Yes, I daresay vernalisation is mainly a dead end as far as Lamarckism goes.
January 19th, 2008 at 11:32 am
I had a look at the Economist article. Very interesting, but much too early to say anything definitive about implications for Lamarckism. Let’s wait and see.
January 19th, 2008 at 11:44 am
Another point: it has of course been known for a long time that “cytoplamic inheritance” via the cytoplasm of the egg cell is possible. Although cytoplasmic inheritance is extra-chromosomal and not governed by Mendel’s laws, it does not amount to Lamarckian evolution.
January 21st, 2008 at 5:45 pm
Work with me here:). After all Einstein didn’t wait for light speed to be proved constant to start calculating the ramifications - He made it an assumption and put it straight into his equations and thought experiments to see what the results would be. What we have here is similar. In certain circumstances, evolution appears too quick to be explained solely via mutations undirected by the environment directly. (Light speed did not seem to be relative to an ether, but absolute)
Lamarckian adaptations by my thought experiments are also quite counter-intuitive and often would go in an opposite direction to “training” adaptation. A training adaptation if immersed in darkness would be to have a dark-adapted eye. A Lamarckian adaptation would be to not bother with sight at all to save resources for all the other senses. The traditional Giraffe example is also wrong. A “training” adaptation would be to stretch a neck. Genes for a taller body is much more likely to be a Lamarckian response to starvation, than to constant reaching for higher food.
January 22nd, 2008 at 9:52 am
There are two components in your argument.
1. “This hinges on whether experiences within a lifetime suitably predict conditions for the offspring of well into the future. If there are *definitive* environmental signals of a long-term change in local habitat, then Lamarckism would be an advantage to species which develop a trigger for generating a portion of offspring with suitable genetic variance in a particular direction, set off by that signal.â€
This, I believe, would be possible only if past situations have occurred (in geologic history) which have “programmed†organisms to foresee such situations. In other words, the “situations†must be recurrent. This has nothing to do with Lamarckism.
2.) “In certain circumstances, evolution appears too quick to be explained solely via mutations undirected by the environment directly.â€
This is an important point. However, recent theoretical studies have shown that evolution can be very fast, because very few mutations are necessary for complex characters to evolve. I have discussed this in my book “Nonequilibrium Ecologyâ€. Here are brief extracts:
“The approach of NKS (”New Kind of Science”, Wolfram 2002), and in particular the use of cellular automata as applied by Wolfram (1986, 2002), is potentially very significant as well. The basic idea of NKS is to run many computer programs based on different “rules”, and to see how they behave. A cellular automaton consists of rows of cells; each cell has a state associated with it, for example, either black or white. Arbitrary rules specify how the automaton develops, i.e., how a cell evolves from one computational stage to the next, based on its previous state and that of its neighbours. Extensive studies have shown that very simple rules (as measured by the number of instructions) lead to simple repetitive patterns, but that a slight increase in a rule’s complexity may lead to very complex, apparently random (or better pseudo-random) patterns. Increasing the complexity of rules above a certain threshold does not lead to a further increase in the complexity of patterns. ………..
“The evolutionary process can be interpreted as random searches for programs carried out in order to maximise fitness. If rules are simple, iterative random searches may find the best solutions relatively fast, but if rules become even slightly more complex, an astronomical number of steps are necessary to even approach an optimal solution. Hence, most species (”programs”) are unlikely to be optimally adapted to their niche, they are trapped in suboptimal niches that were easy to find (Wolfram 2002).
The number of mutations in the course of evolution has been huge, and because relatively simple rules may lead to complexityâ€â€¦â€¦..
“ Furthermore,.such patterns closely correspond to patterns generated by randomly chosen cellular automata with simple rules (also suggesting that genetic programs for the patterns are short). Finally, the pigmented shell of certain species is covered (i.e., at least partially obscured) by living tissue, making it unlikely that natural selection is responsible for the evolution of pigmentation patterns……
The relative frequency of simple organisms, and the existence of organs that have some reasonably simple components, may be explained by the assumption that only simple features on which selection can act, can be optimised and have therefore survived. In toto, natural selection does not lead to complexity but tends to avoid it. The fact that evolution has led to many complex organisms, in addition to many simple ones, is a consequence of the random addition of more and more “programsâ€, many of which happen to lead to complex features.â€
“Kauffman (1993) doubted the overriding importance of natural selection and, like Wolfram, concluded that many traits of organisms have evolved not because but in spite of natural selection.â€
For further details see “Nonequilibrium Ecology“.
January 23rd, 2008 at 11:34 am
This, I believe, would be possible only if past situations have occurred (in geologic history) which have “programmed†organisms to foresee such situations. In other words, the “situations†must be recurrent. This has nothing to do with Lamarckism.
You are confusing me a little bit. I am saying that organisms are programmed to foresee situations, but in a directed mutation sense. You have mentioned that an organism under stress tends to have more mutations. I am saying that the range of mutations evident will be different depending on the particular environmental stress. I am saying that they will be *Appropriately* different depending on the stress one is talking about. I am theorising that the mechanism is programmed inside RNA rather than DNA. How does this not have anything to do with Lamarckism? The fact that I believe there is always a random component to mutations doesn’t change the fact that I believe there is always a non-random component. The non-random component of mutations is based on recurrence of events that may have last happened thousands of generations before.
The evolutionary process can be interpreted as random searches for programs carried out in order to maximise fitness
Maybe I’m talking about non-evolutionary mutations, or regressive evolution or something else rather than Lamarckism - But it sure feels like Lamarckism
January 24th, 2008 at 1:30 pm
From wikipedia - http://en.wikipedia.org/wiki/Inheritance_of_acquired_characteristics, it appears that I am not really talking about Lamarckism (mostly). My belief is that inheritance of acquired characteristics as described doesn’t generally happen, because an organism that does that would be in general genetically “unfit” - Not (I believe) because it is impossible. There are very few natural situations where a phisiological adaptation in an individual would be a signal that its offspring would be better off with that adaptation hard-wired. Much like in computing analogy, while it is entirely possible to hardwire wordprocessing into computers, but it makes no economic sense to. It is because conditions for offspring are likely to be much the same as for their parents, that their genetics are copied so faithfully.
What I am talking about more generally, could be more accurately described as regressive evolution. Essentially, the genes are already there. The guided mutations would in general just switch on or switch off certain functions with certain physiological stimuli. The strength of the link between the mutation and the stimuli would be the historical correllation between the signal and the usefulness of the mutation.
For instance, I would bet my left elbow that genetic eye defects would be hugely more common with progeny of individuals that have been in darkness their whole lives, compared to control groups with whatever other stresses applied. I would think that any biologist that proves such would get a Nobel Prize for it too!
January 29th, 2008 at 3:31 pm
This comment was, by mistake I assume, put under my post “Berühmte Zitate…..” by Marco Parigi.
Marco Parigi Says:
January 29th, 2008 at 3:06 pm e
I’m not sure if it was appropriate to comment here, but I’ve put together my thoughts on inheritance of acquired characteristics at http://marcoparigi.blogspot.com/2008/01/marconomic-theory-of-regressive.html
I’ve called it regressive evolution because of a lot of the falseness in associations with the “L†word. Some of my points might fit in with what you have researched in non-equilibrium biology. Some of them may or may not challenge current thinking in biological circles.
February 2nd, 2008 at 9:59 am
http://en.wikipedia.org/wiki/Adaptive_mutation
February 2nd, 2008 at 11:57 am
Very interesting and relevant
February 5th, 2008 at 3:29 pm
2nd draft “Marconomic Theory of Regressive Evolution”
Mainly for clarification, disambiguation and to match experimental evidence?
My theory, is concerned with “Macro mutations” and in its plainest form just expands on what is already known. I will use the term DNA subroutine for a gene that can be switched on or off to express the macro mutation in question.
Fact: an organism under stress exhibits considerably higher mutation rates.
Theory: Different types of stresses will confer different spectrum of mutation - ie. the mutations will favour more likely beneficial mutations for a predicted future requirement which the stress would signal.
The mechanism proposed is that over a window of genetic experience (say a million years) the DNA stores information regarding which mutations were more appropriate for the given stress and which ones weren’t. A “bank” of hundreds of thousands of DNA subroutines that has built up over time and proved their worth are either expressed or switched off to save metabolic resources. If a subroutine has been switched off long enough it can be relegated to “junk DNA” status and will not further be trusted in the field due to it being no longer valid in the new context (or from an orthodox perspective become unusable due to genetic drift)
A word on micro mutations:
Micro mutations are classified as completely random errors in duplication of genes. These are strongly evident and well studied. However, the orthodox view is that the only way for these micro mutations to avoid eventually destroying the function of the gene in question is for them to be field tested by natural selection. To put it another way, the whole organism has to die before reproducing to avoid one crucial micro mutation from being copied. I find this argument incomprehensible. It is like as if the only way to avoid errors in programming the oxygen intake valve of the space shuttle is to launch it anyway, let it crash and avoid using those blueprints again. I call it the crash, burn and learn concept. It might be alright for a virus with millions of launches every second, but I don’t think it would quite be so good for the Emperor Penguin.
This lends itself to my belief that there is something else at play other than natural selection. There must be some sort of error correction or testing mechanism on individual DNA subroutines, and if there is, they can just as easily apply to non-expressed genes.
April 8th, 2008 at 2:17 pm
I’ve found another interesting article regarding epigenetics and Lamarckism at: http://neuroanthropology.wordpress.com/2008/04/07/the-buzz-about-epigenetics-genes-behaviour-and-the-environment/