Does Darwin need a rethink?


The modern synthesis of evolutionary biology, which was developed in the 1930s and 1940s, is a well-established and widely accepted framework for understanding how evolution works. However, in recent years, there has been growing recognition that the modern synthesis does not fully account for all of the evidence that we have about evolution. As a result, there has been a call for an "extended evolutionary synthesis" (EES) that would incorporate new findings from fields such as evolutionary developmental biology, epigenetics, and population genetics.

The extended evolutionary synthesis (EES) is a new framework for understanding evolution that incorporates insights from developmental biology, ecology, and other fields. The EES emphasizes the role of developmental processes in shaping evolution, and it predicts that variation is more predictable and selection pressures less exogenous than hitherto thought.

The EES has three core assumptions:

  1. Development is not predetermined. The development of an organism is not simply a matter of following a pre-programmed set of instructions. Instead, development is influenced by a variety of factors, including the environment, the organism's genes, and its own behavior.

  2. Variation is not random. Variation in traits is not simply a matter of chance. Instead, variation is often caused by developmental processes, such as genetic mutation, gene expression, and epigenetic inheritance.

  3. Selection is not exogenous. Selection pressures are not simply imposed on organisms from the outside. Instead, organisms can actively modify their environments, which in turn can change the selection pressures they face.

The EES makes a number of novel predictions about evolution. For example, the EES predicts that:

  • Variation in traits will be more predictable than previously thought.

  • Selection pressures will be less exogenous than previously thought.

  • Evolution will be more rapid and flexible than previously thought.

  • Organisms will be more active participants in their own evolution than previously thought.

  • Constructive development: This is the idea that organisms are not simply passive recipients of evolution, but that they actively shape their own evolution through their behavior and interactions with the environment.

  • Reciprocal causation: This is the idea that the environment and the organism are constantly co-evolving, with each influencing the other.

  • Multilevel selection: This is the idea that natural selection can operate at multiple levels, including the individual, the group, and the population.

  • Evolvability: This is the ability of a population to change over time in response to selection.

Here are some additional details about the EES:

  • Developmental bias: Developmental bias is the tendency for organisms to develop in certain ways, even in the absence of direct selection pressures. For example, the development of the human hand is biased towards being opposable, even though there is no direct selection pressure for opposable thumbs.

  • Inclusive inheritance: Inclusive inheritance is the transmission of genes, traits, and information across generations, not just from parents to offspring. For example, the social learning of foraging techniques by young birds is an example of inclusive inheritance.

  • Niche construction: Niche construction is the modification of the environment by organisms. Niche construction can have a profound impact on evolution, as it can create new selection pressures and opportunities for adaptation.

It is a more comprehensive and integrated approach to evolution than the Modern Synthesis (NeoDarwinism),  and it has the potential to explain a wider range of phenomena. The EES is still under development, but it is already having a significant impact on evolutionary biology.

There are several reasons why an EES is needed. First, the modern synthesis focuses primarily on the microevolutionary process of natural selection, but it does not adequately address the macroevolutionary process of speciation. Speciation is the process by which new species arise, and it is a complex process that involves many factors, including natural selection, genetic drift, and gene flow. The EES would provide a more comprehensive framework for understanding speciation.

Second, the modern synthesis assumes that genes are the only important unit of inheritance, but recent research has shown that epigenetic factors, such as DNA methylation and RNA interference, can also play a role in inheritance. Epigenetic factors can affect the expression of genes, and they can be transmitted from parents to offspring. The EES would incorporate epigenetics into our understanding of evolution.

Third, the modern synthesis assumes that natural selection is the only important force driving evolution, but recent research has shown that other factors, such as niche construction and group selection, can also play a role. Niche construction is the process by which organisms modify their environment in ways that affect their own evolution. Group selection is the process by which natural selection can favor traits that benefit the group, even if they do not benefit the individual. The EES would incorporate these other forces into our understanding of evolution.

In 2014, a group of scientists published an article in Nature titled "Does evolutionary theory need a rethink?" The authors argued that the modern synthesis, the prevailing theory of evolution, is incomplete and needs to be updated to account for recent advances in biology.

The modern synthesis is based on the idea that evolution is driven by natural selection, which is the process by which organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits. The modern synthesis also recognizes the importance of other factors, such as genetic drift and gene flow, in shaping evolution.

The authors of the Nature article argued that the modern synthesis neglects several key processes that are important for understanding evolution. These processes include:

  • Developmental plasticity: The ability of organisms to change their phenotype, or physical appearance, in response to their environment.

  • Epigenetics: The study of how changes in gene expression can be inherited from one generation to the next, even without changes in DNA sequence.

  • Culture: The transmission of information between individuals through non-genetic means, such as imitation and teaching.

The authors argued that these processes are important for understanding how evolution works in the real world. For example, developmental plasticity can allow organisms to adapt to changing environments more quickly than natural selection alone. Epigenetic inheritance can allow organisms to pass on traits that are not encoded in their DNA, such as resistance to disease. And culture can allow organisms to evolve new traits much more rapidly than natural selection alone.

The authors of the Nature article called for a new theory of evolution that would incorporate these neglected processes. They called this new theory the "extended evolutionary synthesis."

The extended evolutionary synthesis has been met with mixed reactions from the scientific community. Some scientists have welcomed the call for a new theory of evolution, while others have argued that the modern synthesis is still a valid framework for understanding evolution.

The debate over the extended evolutionary synthesis is likely to continue for some time. However, the article in Nature has helped to raise awareness of the importance of these neglected processes for understanding evolution.

The question of whether we need a new theory of evolution is a hotly debated topic in the scientific community. Some scientists believe that the modern synthesis, which was developed in the 1930s and 1940s, is still the best explanation for how evolution works. Others argue that new discoveries in areas such as epigenetics, gene regulation, and evolutionary developmental biology (evo-devo) require a major overhaul of evolutionary theory.

One of the main arguments in favor of a new theory of evolution is that the modern synthesis does not adequately explain the role of genes in evolution. The modern synthesis assumes that genes are the only important factor in evolution, but new research suggests that genes are not the only players. For example, epigenetics is the study of how changes in gene expression can be passed down from parent to offspring, even without changes in the DNA sequence. This suggests that the environment can also play a role in evolution.

Another argument in favor of a new theory of evolution is that the modern synthesis does not adequately explain the rapid pace of evolution in some cases. For example, some species have evolved to become resistant to antibiotics in a very short period of time. This suggests that natural selection can sometimes operate at a much faster pace than previously thought.

The debate over whether we need a new theory of evolution is likely to continue for many years to come. However, it is clear that new discoveries in evolutionary biology are forcing scientists to rethink some of the basic assumptions of the modern synthesis. It is possible that a new theory of evolution will emerge in the near future, but it is also possible that the modern synthesis will be able to accommodate the new discoveries without major revision.

Here are some of the key points of the debate:

  • Supporters of the modern synthesis argue that it is a well-tested and successful theory that has explained a wide range of evolutionary phenomena. They also argue that there is no need to replace a theory that is working well.

  • Proponents of a new theory of evolution argue that the modern synthesis is not able to explain some of the most important aspects of evolution, such as the role of genes and the rapid pace of evolution. They also argue that the modern synthesis is too narrow in its focus and does not take into account other factors, such as the environment and development.

The debate is likely to continue as scientists continue to learn more about the process of evolution.



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