The Illusions of the Modern Synthesis - review
The Illusions of the Modern Synthesis Unveiling the Cracks in Evolutionary Theory
In his 2021 article published in Biosemiotics, Denis Noble, a renowned British cardiologist and cell physiologist, argues that the Modern Synthesis, the dominant evolutionary theory of the 20th century, is riddled with fundamental flaws. He identifies four key illusions that have underpinned the Modern Synthesis, each rooted in misinterpretations of molecular biology:
The Illusion of Natural Selection: Noble contends that natural selection, as traditionally understood, is insufficient to explain the complex and coordinated features of living organisms. He argues that selection operates on pre-existing functional systems, not on random mutations, and that cooperation and self-organization play crucial roles in evolution.
The Illusion of the Weismann Barrier: This barrier, proposed by August Weismann in the 19th century, posits a strict division between germline and somatic cells, preventing the inheritance of acquired traits. Noble challenges this notion, citing evidence of epigenetic modifications and intercellular communication that blur the lines between germline and soma.
The Illusion of Darwin's Gemmules: Charles Darwin's hypothetical gemmules, particles carrying inheritable information, were rejected by the Modern Synthesis in favor of purely genetic inheritance. Noble, however, argues that recent discoveries in epigenetics and cell signaling via Extracellular vesicles (EVs) lend credence to the idea of non-genomic inheritance mechanisms, reviving the concept of gemmules in a modified form.
The Illusion of the Central Dogma: Francis Crick's Central Dogma, which dictates a one-way flow of information from DNA to RNA to protein, is another cornerstone of the Modern Synthesis. Noble criticizes this dogma as overly simplistic, highlighting the dynamic interplay between genes, environment, and cellular processes that shapes development and evolution.
These illusions, Noble argues, have led to a reductionist view of life, neglecting its inherent complexity, dynamism, and organismal autonomy. He calls for a new synthesis, one that integrates insights from molecular biology, biosemiotics, and other fields to create a more comprehensive understanding of evolution.
Beyond the Illusions: Embracing a New Synthesis
Noble's critique has sparked a lively debate among evolutionary biologists. Some have dismissed his claims as unfounded or overly speculative. Others, however, acknowledge the limitations of the Modern Synthesis and welcome the call for a broader framework.
Several promising avenues are emerging for a new synthesis:
Evo-Devo (Evolutionary Developmental Biology): This field bridges the gap between genetics, development, and evolution, exploring how genes interact with the environment to produce diverse phenotypes.
Epigenetics: The study of heritable changes that don't involve alterations in DNA sequence is shedding light on non-genomic inheritance and its potential role in evolution.
Biosemiotics: This field examines the role of signs and communication in living systems, offering a framework to understand how organisms interpret and respond to their environment, shaping their evolution.
A Paradigm Shift in the Making?
The Modern Synthesis has served as a framework for understanding evolution for decades. However, Noble's critique and the emerging research in Evo-Devo, epigenetics, and biosemiotics suggest that it may be time for a paradigm shift.
A new synthesis, informed by these fields, could lead to a more nuanced and dynamic understanding of evolution, one that recognizes the inherent complexity of life, the interplay between genes and environment, and the organism's active role in shaping its own destiny.
The Illusions of the Modern Synthesis: A Call to Action
Noble's article is not merely a critique; it is a call to action. He urges biologists to move beyond the limitations of the Modern Synthesis and embrace a more holistic and inclusive understanding of evolution. This requires collaboration between diverse disciplines, openness to new ideas, and a willingness to challenge long-held assumptions.
The journey toward a new synthesis will not be easy. It will require overcoming ingrained biases, reconciling seemingly contradictory findings, and forging new paths of inquiry. But the potential rewards are immense: a deeper appreciation for the wonder and complexity of life, a more accurate understanding of our place in the universe, and perhaps even the key to unlocking the mysteries of human evolution and development.
In conclusion, Denis Noble's "The Illusions of the Modern Synthesis" is a thought-provoking and timely intervention in the ongoing debate about evolution. It challenges us to re-examine our fundamental assumptions and embrace the complexities that lie beyond the illusions. The pursuit of a new synthesis is not about abandoning the valuable insights of the past; it is about building upon them, expanding our horizons, and ultimately, arriving a a new synthesis.
Article Snippets
The Modern Synthesis has dominated biology for 80 years.
When first formulated in the 1950s these discoveries and concepts seemed initially to completely justify the central genetic assumptions of the Modern Synthesis.
the Central Dogma was viewed as supporting the Weismann Barrier, so excluding the inheritance of acquired characteristics.
It may be hard to believe that science itself could be taken in by illusions and by its own use of language. Yet, that is precisely what I think happened in the development of the Modern Synthesis.
. I believe all the distinguished scientists involved were genuinely convinced of their facts and theories.
we can all be taken in by our culturally-inherited illusions without realising that is what they are. Metaphors and analogies can become linguistically ‘dead’
In the case of “the Selfish Gene” (Dawkins 1976, 2016), its author, Richard Dawkins, even stated initially that he thought it was “the literal truth” (Dawkins 1981). I don’t think he believes that now.
I am not accusing anyone of deliberately trying to mislead people. All the people involved are leading scientists. My argument is that language itself contained the seeds of the problem. That makes it even more important to re-examine the language of biology. The four illusions are: 1. Natural Selection; 2. The Weismann Barrier; 3. The Rejection of Darwin’s Gemmules; 4. The Central Dogma.
major discoveries of molecular biology undermined the Modern Synthesis, even though that was not appreciated at the time.
Since its original formulation there have been proposals to extend the Modern Synthesis: the Extended Evolutionary Synthesis, EES
The illusions to which I refer stem from the original 1942 Modern Synthesis, as they are presented in textbooks and popularizations even today
There is no actual selection carried out by natural ‘selection’. Nature – in this case the different rates of survival – is simply a passive filter. Yet it is often presented as the active driver of evolution.
There are active drivers of evolution, to which I will return later, but it is an illusion to think that ‘blind’ natural selection is really ‘selecting’ or could be an ‘active’ driver
It is an illusion with important consequences because it can lead people to think that real selection, by organisms themselves with the power to do so, cannot even exist.
That idea is itself an illusion generated by a conceptual mistake, which is to confuse the metaphor of selection with reality.
If all evolutionary change is produced by natural (unintended) selection, then no organisms can have the power of real, intended selection
have been one of the drivers of the Cambrian Explosion. If so, one of the most important transitions in evolution was actually driven by organism agency, not by natural selection
Genes, for example, or any other molecules, certainly cannot carry intentionality. Organisms and groups of organisms do that.
The illusion here is that this disproves what the French biologist, Jean-Baptiste Lamarck, thought. But Lamarck didn’t think that at all! That is a straw man in this case. What he really thought was that changes developed during life that were a functional advantage to an organism could be inherited precisely because they were a functional advantage.
The way to test that idea was pioneered by Conrad Waddington over 50 years ago
EES or EIS referred to in the Introduction. Both seek to include trans-generational epigenetic inheritance in evolutionary theory. That transgresses a foundational feature of the Modern Synthesis, which was based on combining the Weismann Barrier with Mendelian genetics
Charles Darwin was a slow but deep thinker. Since he thought, like Lamarck, that functional changes in organisms could be inherited,
Darwin used a similar logic to Harvey. He supposed that very tiny particles in the body, which he called gemmules (Darwin 1868), could communicate between the body and the germline
we are now able to see what we call extracellular vesicles (EVs, sometimes also called exosomes) pouring out of living cells.
packets of chemicals including DNAs and RNAs that give a snapshot of the regulatory state of the cells from which they come.
Are they Darwin’s gemmules, communicating with the germline? Well, they can pass straight through Weismann’s so-called barrier and carry their information to the germ cells.
If he were alive today he would be celebrating the vindication of his 1868 idea
So also would Lamarck with his idea of “subtle fluids
The Central Dogma of Molecular Biology has a claim to be the greatest illusion ever created in biology.
It is so important and, as its name suggests, central to neo-Darwinist thought
That can be done only by realising that there is a very deep illusion here. The illusory straw man was built in stages by various people at different times. I don’t think any one of them fully intended the complete illusion. Each step became fully embedded in the standard story until it was no longer questioned
There seems therefore to be a direct clash between the McClintock and Shapiro’s work and the standard interpretations of the Central Dogma.
A multi-level view of biology that avoids necessarily privileging any level also avoids the relevant linguistic traps.
“The Central Dogma: A Joke that Became Real.”
The scientists who developed the Modern Synthesis were brilliant and they were amongst the most influential scientists of the twentieth century.
The Modern Synthesis was perceived to fit extremely well with the early discoveries of molecular biology.”
Gene-centrism is an important legacy of the Modern Synthesis, which has had influence way beyond the subject of evolutionary biology
Many of the biological facts I have noted in this article have been known for many years. Yet the illusions that they undermine have nevertheless been strongly maintained as part of the orthodoxy of evolutionary biology.
A collaboration between philosophers and scientists is necessary to tidy up the language of biology and make it fit for the twenty-first century.
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