Changes In The So Called "Darwinism": A Response To The Article From The Conversation
Today I am not focusing on a creationist claim, article nor video - quite the opposite, actually. Recently I stumbled across the article: Updating Darwin: biologists are returning to an older theory to explain anomalies in evolution. The article is dedicated to a thesis that modern evolutionary theory requires changes as new mechanisms previously not known to exist are being discovered and they're heavily to previously rejected ideas of inheritance known as Lamarckism. This indeed is the case and these mechanisms are gradually incorporated into our current understanding of evolutionary processes. Initially (and especially to a person not educated on the topic), it looks like a standard article about science that may be at best slightly oversensationalized. However, at a closer look it becomes more clear that it contains some information that is either misleading or incorrect.
Fortunately, it isn't written to discredit evolution as the article starts with a line: "Evolution is a fact of life". The first piece of misleading claim comes from this line: "Darwin’s ideas were built around natural selection, which says that some individuals within a species are born with differences that lead them to perform better and therefore reproduce more than others." On the surface level this claim seems fine unless we dig a bit and focus on the last part. This sentence claims that natural selection favors individuals who have more offspring. Technically, it is true. If we understand it to mean that favored genotype will eventually produce more offspring over many generations than the unfavored one, then yes, it is indeed true. However, it can be easily misunderstood. You see, some people may take it to mean "if a given individual gives birth to more offspring at once or during lifetime it will be favored". Unfortunately, that is not true. Natural selection typically favors organisms that possess greater reproductive success which means how many offspring that organism produces but also how many of these offspring will reproduce themselves. It is also important to mention that a better measurement of which trait is favored by this mechanism is fitness since unlike reproductive success of an individual it is not affected by random events but rather is a quantitative representation of adaptive strength. This allows evolutionary theory to explain phenomena such as sex differentiation and heavy offspring investment.
Simple graphic explanation of natural selection
In comparison to organisms such as bacteria that reproduce asexually, sexually reproductive species produce fewer offspring. The same thing is true in regards to sex differentiation and heavy offspring investment. If evolutionary theory was indeed predicting that adaptations leading to a smaller amount of offspring were always discouraged this would be a direct contradiction to evolutionary theory. However, it isn't as these traits can in certain contexts allow individuals to reach greater success. For instance, imagine a species X with two different phenotypes: phenotype A produces 10 000 offspring per breeding event but only 1 individual offspring survives and phenotype B that produces 100 offspring but 10 of those offspring survives. Which of these phenotypes will be favored? The answer is obviously B as it will quickly dominate the gene pool of species X because there will be much more successfully reproducing individuals with B phenotype than with A phenotype despite the fact that individuals with phenotype A will at once produce 100 times more offspring. Surely, increasing the number of offspring can be beneficial as well but it isn't an inherently beneficial pattern to every single niche or environment.
That's why the previously mentioned sentence should end with something closer to: "therefore reproduce more effectively than others" or "therefore produce more offspring that can survive long enough to reproduce". This allows us to lower the chance of misunderstanding and this article being used as a tool of promoting pseudoscience. The latter scenario is more important here as I personally witnessed creationists claiming that existence of sexually dimorphic species is a BIG PROBLEM for evolution since males don't give birth. This implies that increase of number of offspring is always favored by natural selection regardless of fitness landscape which is simply objectively false (as explained above). Because of that I can absolutely envision creationists using this article as a quote mine to prove that "EVOLUTION HAS BIG BAD PROBLEMS". Even though the author clearly doesn't even imply that.
Next piece of incorrect information is even more subtle, but nevertheless worth discussing. The author writes: "Over time, Lamarck’s idea was discredited. A key moment was an experiment performed by Germany’s August Weismann in 1904. He surgically removed the tails of adult rats before allowing them to reproduce, expecting to see this change inherited by their offspring". The experiment did indeed happen but rats were not the subject of it. August Weismann in fact used white mice in his experiment. The text continues with following: "But it never happened, despite him removing the tails of many generations of rats. Lamarckism as understood then would have predicted that the offspring should have been born with no tails, so for many years biology textbooks presented his theory as a firmly refuted hypothesis". I certainly remember learning about this experiment during my biology class focused on the development of evolutionary thought. It may seem as a nitpicking but this experiment can be considered a bit problematic in relation of refuting of Lamarckism. You see, Lamarckism assumes the existence of the mechanism of "use and disuse". This means that beneficial traits emerge or improve during lifetime of an organism and are later passed down into the offspring while detrimental traits are subjected to the opposite effect. The problem is that the way by which traits are under control is dependent upon solving a certain environmental obstacle due to internal goals of a given individual. Simply put, artificially cutting out an animals body part is an external factor and not something that is meant to solve a certain problem due to specific goals of a given organism.
It is absolutely true that this experiment was and is still used to discredit Lamarckism (especially in school textbooks) but as explained above it is not that great of evidence than many people think it is. Does that mean that Lamarckian modes of inheritance can still realistically be at least a main driver of evolutionary adaptation? Absolutely not! There are actually other experiments that take into consideration the mechanism of use and disuse and... reveal that Lamarckism is contradicted by the results. The one I'll present here was carried out by W. E. Agar and coworkers as an attempt of replication of the famous McDougall's experiment.
Representation of McDougall's experiment on a YouTube video's thumbnail
The original experiment involved putting rats in an enclosure filled with water. Rats were able to escape via two different gangways: one with no light which is safe and an illuminated one which releases electric shock upon entering. Rats had to learn which route is safe to follow. This actually created a clear setting in which the mechanism of use and disuse could hypothetically work - rats had an internal goal of finding safe exit as they just as many other animals desire to avoid pain and thus by the logic of Lamarckian mechanism they should gradually develop neuronal structure that would improve their learning skills over generations. McDougall claimed that his experiment proved that rats had evolved to learn to find safe gangways much more quickly than their ancestors without the work of natural selection (as there was supposedly no selective breeding involved which would be Darwinian in nature).
However, when W. E. Agar's team carried out their experiment (which actually consisted of control and trained sublines while original experiment only consisted of trained line) they found no valid evidence of Lamarckian method of inheritance. It turned out that after around 5 generations rats didn't show any signs of improved learning over generations. After around 20 years of the experiment the rats actually showed improved learning skills but this effect was:
1. not persistent in contrast to the mechanism of use and disuse which would dictate that this adaptation would persist in this setting
2. also shown by untrained (control) sublines which meant the mechanism behind such seeming adaptation was not Lamarckian as it was equally expressed by lineages that were inclined to adapt and those who weren't.
The authors concluded that alleged Lamarckian adaptation was actually a result of... fluctuating population health - rat colonies are subjected to periods of deterioration and healing. This (and other such experiments) showed that supposed inherited learning enhancements were merely statistical artifacts and reliable observations showed no correlation between rat lineages/sublines being trained or not. In conclusion, more reliable experiments showed no basis for validity of Lamarckian mechanism of inheritance. So while the author is correct in the notion that the Weismann's experiment has historically largely discredited Lamarckism in the scientific community I decided to use imperfections of that experiment as a learning opportunity for readers of this article.
And now comes the time to mention the main reason why I decided to write this article. Namely, the section title: Where Darwinism falls short. The reason I dislike this title is due to the usage of the term "Darwinism". While some people may think that this is a standard term for modern evolutionary theory, it really isn't. The term was historically used to describe evolutionary theory but currently it is considered to be outdated and it thus makes more sense to use "Darwinism" to describe earlier theories which predate modern evolutionary theory (including modern synthesis). The term is, however, frequently used by creationists as a standard description of modern evolutionary theory. It is also used by them to describe unrelated concepts such as abiogenesis or cosmic evolution. It allows them to more easily perpetuate a notion that "atheists" (even though atheists don't even form majority of people who accept evolution) simply believe in something merely because of what Darwin said and thus anything immoral or incorrect that was presented by him must be equally believed by them and because of that evolution must be rejected alongside these outdated ideas. In that sense Darwinism is conceptually similar in their minds to atheism, nazism, communism, satanism, Marxism, transgenderism, islamism or evolutionism - just another "ism" they can more easily ignore by associating it with concepts they already view as baseless, ridiculous or immoral. Due to this phenomenon it is important to avoid misusing this term in describing modern evolutionary theory. The article should then use other terms such as "current evolutionary theory", "Modern Synthesis", "modern evolutionary theory" or "standard evolutionary understanding" since they avoid the possibility of being misused by groups propagating pseudoscience. Another term that is actually more frequently used in scientific context is "Darwinian evolution". It also makes more sense to use it in such article as Darwinian evolution is an umbrella term that encompasses Darwin's theory and later theories that stem from Darwin's work (including modern evolutionary concepts).
Elderly Charles Darwin
Next we stumble upon this line: "Beyond epigenetics, the passing down of learned skills from one generation to another is also a form of Lamarckism". That is simply not true. Learned behaviors are not and have never been considered to be a part of Lamarckism. Lamarckism mainly focuses on inheriting acquired physical traits. Learned behaviors don't fit into that category as learning from parents is not considered a form of evolution and thus can't be treated as a form of Lamarckian inheritance as well. Evolution is defined as changes of heritable characteristics of organisms in populations over generations (for further clarification on what evolution is and isn't visit What does 'evolution' even mean?).
Heritable characteristics usually encompass traits that are directly inherited epigenetically and genetically. Because of that classification learned skills are not considered to be heritable. The only way passing down learned skills could be considered Lamarckian if a parent learned a given skill and later passed it down to offspring without that offspring needing to learn this skill independently. So for example if some kind of change in epigenetic markers would trigger an automatic development of a skill in the offspring this would be considered Lamarckism. I also want to point out that this specific part refers to specific learned behavior and not to the capacity to learn and changes of it. If a jackdaw chick receives a mutation from a parent that makes it better at learning that's evolution but if it is just a regular chick and learns a skill from a parent it has nothing to do with evolution.
Next section of the article is focused on combining Lamarckism with modern Darwinian evolutionary theory. The only problem I want to point out here is a bit of semantic one. The author accurately explains why Lamarckian mechanism or inheritance is compatible with natural selection - if passing down certain mechanisms that can allow for Lamarckian inheritance of traits is beneficial (such as the example of Caenorhabditis elegans that can pass beneficial RNAs to its offspring) it will be favored and thus can evolve as an adaptation. That is certainly the case as natural selection is a standard mechanism used to explain existence of adaptive traits. The author, however, uses the term "prediction": "In other words, Darwinism actually predicts that this Lamarckian capacity should evolve". This implies that we should expect these adaptations to emerge. And in fact one user apparently understood it to mean exactly that as he wrote in the comment section: "As the article says ‘In other words, Darwinism actually predicts that this Lamarckian capacity should evolve.’ So if Darwinism predicted it, it sounds like a win for Darwin". This user misunderstood that fragment as meaning something contradictory towards the main theisis of that article. That is in my opinion problematic as it makes it sound like us not finding Lamarckian mechanisms in nature would falsify the modern theory of evolution. That is simply incorrect as there is no basis to predict that these mechanisms HAD to emerge. They certainly could and are explainable but it doesn't mean they are an inherent result of natural selection. Similarly, we observe that organisms routinely adapt to their environments on a microevolutionary scale thus we should see adaptive traits on macroevolutionary scale as it is usually just microevolution working "long enough". However, this doesn't mean that we predict that birds or whales with their unique adaptations would have to exist and if they didn't we would have to reject the theory. Origin of Lamarckism (as a form of inheritance and not in previously mentioned form of hypothesis) is certainly explainable by natural selection but natural selection does not necessitate its emergence.
Last problematic segment I want to bring up is found at the very end. As the author concludes: "The same goes for conservation: scientists in Australia are already exposing coral to heat stress in the laboratory to trigger epigenetic responses that make them more resilient to heatwaves. And if human parental behaviours can influence obesity or addiction in their children, then prevention programmes help not only the people that receive them but also future generations". The part about obesity and addiction appears right after example of experiment focusing on transgenerational epigenetic inheritance and thus ties them together. To some it may seem as if inheriting predisposition to obesity or addiction in general is primarily a product of Lamarckism since these conditions result from behavioral patterns and these are somewhat associated with Lamarckian form of inheritance. While the author clearly doesn't claim that passing down predispositions to these conditions is purely due to parental behavior it still may facilitate misunderstandings. Obesity (or more precisely predisposition to obesity) is inherited genetically as well without any Lamarckian mechanisms and many mutations related to inheritance of predisposition to obesity have been identified. Exact same mechanisms are involved in the case of addiction which can be inherited via epigenetic modifications but a large impact on addiction vulnerability comes from genetic factors as well. Another mechanism in addiction may be problematic to ascribe to Lamarckism and that is exposure to addictive substances during prenatal development. While this exposure can be frequent in children of mothers that are addicted it doesn't have to be necessarily the case as exposure (for example resulting in Neonatal Abstinence Syndrome) to substances can occur in children whose mothers were not addicted but merely used addictive substances during pregnancy.
This hardly constitutes a form of Lamarckian inheritance as it does not involve acquisition of these traits during lifetime of parents but rather their independent occurrence in offspring. A better term that could be used here is quasi-Lamarckian inheritance as it has already been used in scientific literature to describe other mechanisms of transgenerational inheritance such as CRISPR-Cas adaptive immunity system in archae and bacteria that produces random variation and involves major contribution from natural selection which selects individuals with highest fitness. CRISPR-Cas is also interesting since it does not involve production of new traits or improvement of previous ones via mechanism of use and disuse but rather uses pre-existing DNA or RNA fragments from viruses by incorporating them (always in a form of DNA) into prokaryotic genome which later allows bacteria or archaea to recognize specific viral genomic sequences during infection and pass this ability to its progeny.
Coming back to obesity and addiction at least in my opinion it would be better to add a fragment regarding other mechanisms of inheritance of predisposition to them. For example: "And if human parental behaviours ASIDE FROM OTHER FACTORS SUCH AS GENETICS can influence obesity or addiction..." would be a more precise way to convey the concept of transgenerational inheritance related to these pathological states.
In my final conclusion of my article I'm asking the author to possibly correct certain mistakes and remove incorrect information since it may mislead typical readers or feed disingenuous internet trolls. Unfortunately, such trolls have already stumbled upon this article as the comment section already has comments spreading misinformation including accusations of using learning of skills as evidence of universal common ancestry by the author which he clearly never even attempted let alone actually did. I also want to point out that my article is not meant to be a form of attack on the author but rather an occasion to avoid issues in future articles.
And here's a picture of Binturong since I recently stumbled upon a drawing resembling this animal.
Sources:
1. Updating Darwin: biologists are returning to an older theory to explain anomalies in evolution: https://theconversation.com/updating-darwin-biologists-are-returning-to-an-older-theory-to-explain-anomalies-in-evolution-276549
2. Natural selection: https://en.wikipedia.org/wiki/Natural_selection
3. Reproductive success: https://en.wikipedia.org/wiki/Reproductive_success
4. Fitness: https://en.wikipedia.org/wiki/Fitness_(biology)
5. Lamarckism: https://en.wikipedia.org/wiki/Lamarckism
6. A First Report on a Test of McDougall'S Lamarckian Experiment on the Training of Rats: https://scispace.com/papers/a-first-report-on-a-test-of-mcdougall-s-lamarckian-2ej2t4upny
7. Fourth (Final) Report on A Test of McDougall's Lamarckian Experiment on the Training of Rats: https://ui.adsabs.harvard.edu/abs/1954JExpB..31..307A/abstract
8. Darwinism: https://en.wikipedia.org/wiki/Darwinism
9. Evolution: https://en.wikipedia.org/wiki/Evolution
10. Obesity: https://en.wikipedia.org/wiki/Obesity
11. Genetics of obesity: https://en.wikipedia.org/wiki/Genetics_of_obesity
12. Addiction: https://en.wikipedia.org/wiki/Addiction
13. [7-6000] Neonatal Abstinence Syndrome (NAS): a modern public health crisis: https://www.judcom.nsw.gov.au/publications/benchbks/children/CPM_NAS.html
14. Does the central dogma still stand?: https://pmc.ncbi.nlm.nih.gov/articles/PMC3472225/
15. CRISPR-Cas immunity in prokaryotes: https://www.nature.com/articles/nature15386
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