Evolutionary theory is in growing ferment. And few people are paying attention. At least two biologists have shouted from megaphones. Biologist Robert Reid in his 2007 book screamed about the need for a new synthesis. He talked about how many issues across biology at that time that he listed as “[p]ost-Lamarckism, structuralism, complexity theory, the lucky-strike paradigm of neo-catastrophism, evo-devo, and symbiosis studies.” He then went on to warn that: “But their individual adherents, whether modern mutineers or postmodern privateers, lack the resolve to escape the vortex of Darwinism. If they do not all hang together in a new synthesis they will all hang separately, to be scavenged by the Modern Synthesis, stuck in the hold, and forgotten.” (Reid 2007, p. 422).
Another biologist, Scott Turner, in 2017 is equally distraught. He states that: “I have come to believe that there is something presently wrong with how we scientists think about life, its existence, its origins, and its evolution” (Turner 2017, p. xi).
Yet another biologist, Denis Noble, calls for a replacement for the current theory rather than just a slight modification. He justifies this as: “The reason is that the existence of robust mechanisms of trans-generational inheritance independent of DNA sequences runs strongly counter to the spirit of the Modern Synthesis (Noble 2015, p. 7).
Much more common than these biologists who are strongly embracing change are a larger group of biologists that I will call the moderates. They lead a discussion calling for an “extended synthesis,” or, just a slight modification. There are several books and numerous articles on this topic (e.g., Pigliucci & Mueller 2010). It appears to be a stalled disagreement. Within this discussion are several theoretical disagreements. A principle one concerns a renewed sense of the important role of developmental biology within evolution in a movement known as “evo-devo.” This has a big literature and a diverse basket of criticisms of how development supersedes the genetics (e.g., Moczek et al 2015). Within this discussion are the related concepts of niche construction and epigenesis. An example of niche construction might be where beavers begin building dams and stick houses, which then has the effect that these environmental structures then change what genes are selected in these artificial environments. Development, or in this case dam-building, has changed the evolutionary trajectory of a species now adapted to lives with dams. The genes are not independent but follow how beavers grow developmentally into their environment. Some people think that this portends a major change in the evolutionary perspective. For example, biologist Sean Carrol thinks that evo-devo is important enough to qualify it as a “third major act” for evolutionary theory after Darwin’s book and after the Modern Synthesis of the 1930s (Carrol 2006). The point here is not to weigh in on these debates but only to note that evo-devo, niche construction, and epigenesis are three areas of debate that have garnered a title of a potential, moderate change in evolutionary theory, or an “extended” synthesis.
There is also a new addition to theory in the form of cultural evolution, which is prevalent with humans. This involves how animals can learn from one another so that they acquire new capabilities (e.g. a chimpanzee using a stick to extract honey from a hive) in what is seen as “inheritance” that can be passed across generations or between acquaintances. Cultural evolution is sometimes included as a related challenge within the discussion of an extended synthesis. Animals and especially humans inherit what we learn from others.
Moving on from the cluster of issues around the importance of development as opposed to genetics in evolution is the large wind from systems biology (Alon 2007). This is systems in the sense of complex adaptive systems. It has moved powerfully into biology with the discovery that many emergent patterns find stabilities of their own within biological networks. For example, gene-protein networks are found not to be simple “instructions” from genes to proteins but to be elaborate and even circular patterns of effects between many genes and proteins. One gene is transcribed as a particular protein which then attaches to a second gene which then goes active or inactive to determine yet a second protein which then … and on it goes until a stable pattern is found for the cell and the gene-protein network. A group of biologists that includes Denis Noble concludes that this alone calls for “a replacement of gene reductionism by systems principles” (Noble et al 2014, p. 2241). More generally complex systems and systems thinking has moved into most academic fields now from theories of weather patterns to how the brain works with neuronal systems. It could itself be a general shift in thinking in addition to revealing a different view of how living organization works.
Also widespread, the theme of self-organization has become prevalent in biological thought (Camazine 2001; Karsenti 2008). The implication is that there is an aspect of self-organization among molecules and components that is independent of the genetic control. Is this true? Does it challenge the current synthesis? So far there is just silence for these questions.
And related to self-organization are the widespread signs that evolutionary forms converge on particular patterns. For example, insects, birds, and mammal lines have produced species that all used the pattern of wings for flight. This notion of evolution going repeatedly into preferred forms or convergence of forms has much evidence (Morris 2009; McGhee 2011). But does it too indicate self-organization in particular directions independent of what the genes do?
Another seeming challenge to our current evolutionary synthesis is the phenomenon of symbiogenesis (Kozo-Polyansky & Margulis 2010). This occurs when two separate species live such tightly coupled lives that they merge to form a new, composite species. The notable examples here come from the formation of nucleated cells that were formed by different types of bacteria living together or inside each other to the point that they merged and their genes merged. This is also called endosymbiogenesis to designate the cases where one species is inside the other as the two merge.
Organisms also apparently have a looser way to live in confederacies, where the survivors are not necessarily the fittest but that are fit by integrating into networks of other species. Bapteste and Huneman (2018) explore these scaffolds for species and submit that it could be a unifying principle for evolutionary theory. And the issues that challenge or could be patches for evolutionary theory continue to multiply.
There is another view of evolution that looks at large scale trends and their abrupt changes as a pattern that needs explanation. Darwinism and genes have never been able to explain these. Two attempts to fill this void deserve mention. Punctuated equilibria was a model of how macroevolution proceeded (Eldredge 2015). The surviving founder of this theory has reformulated his view of macroevolution as hierarchy theory. Niles Eldredge and co-workers (2016) see that evolution occurs not with species but with ecosystems and especially the species component of ecosystems. Another view, major transitions in evolutionary theory (Smith & Szathmary 1999), sees qualitative shifts as part of the big changes over evolutionary history. For example, shifting from single celled species to multicellular species is such an enormous shift in species size, quality, and capabilities that it calls for its own explanation beyond simple genetic mutations. They find eight such major transitions that deserve another explanation of which the current response is to use multi-level selection where selection shifts from the individual organisms to the group. This does not appear to be the last word on this major transitions question.
In addition to these many issues brewing separately across the biological archipelago there are also several large-scale criticisms that remain unanswered. These come from our first two biologists-with-megaphones at the top of this post. For Robert Reid the basic problem is that Darwinism gave a selective account of evolution but left out any generative account that could explain how living forms arose (Reid 2007, p. 15). For Scott Turner the basic problem is that Darwinism covers the inheritance channel of how forms were passed across generations but left out any account of adaptation to form successful whole patterns (Turner 2017, pp. 97, 110, 124, 292). The larger issue from both these critiques is that biology lacks any concept of the nature of life (Smith & Morowitz 2016). This can be seen more clearly from within the ongoing research on the origin of life and that will be taken up in my next post.
This brief overview of some of the bubbling issues within evolutionary theory is meant to give a sense of diverse, under-reported challenges that are also seeds for potential theory modification. My sense of the issues is that there will be a change that will introduce a theory that is more encompassing of such divergent phenomena as listed above. And this possibility deserves more attention and support. The current state where issues bubble without open discussion or integration is not healthy for anyone. An opportunity awaits.
Alon, Uri. 2007. An Introduction to Systems Biology: Design Principles of Biological Circuits. Chapman & Hall/CRC.
Bapteste, Eric & P. Huneman, “Toward a Dynamic Interaction Network of Life to unify and expand the evolutionary theory,” BMC Biology 16(2018):56.
Camazine, S., J-L. Deneubourg, N. Franks, J. Sneyd, G. Theraulaz & E. Bonabeau. Self-Organization in Biological Systems. 2001. Princeton University Press.
Carrol, Sean. 2006. Endless Forms Most Beautiful: The New Science of Evo Devo. W.W. Norton.
Eldredge, Niles. 2015. Eternal Ephemera: Adaptation and the Origin of Species from the Nineteenth Century Through Punctuated Equilibria and Beyond. Columbia University Press.
Eldredge, Niles, T. Pievani, E. Serrelli & I. Temkin. 2016. Evolutionary Theory: A Hierarchical Perspective. University of Chicago Press.
Karsenti, Eric. 2008. “Self-organization in cell biology: a brief history.” Nature Reviews/Molecular Cell Biology. March. V. 9. Pp. 255-262.
Kozo-Polyansky, B. & L. Margulis. 2010. Symbiogenesis: A New Principle of Evolution. Harvard University Press.
McGhee, George. 2011. Convergent Evolution: Limited Forms Most Beautiful. MIT Press.
Moczek, Armin, K. Sears, A. Stollewerk, P. Wittkopp, P. Diggle, I. Dworkin, C. Ledon-Rettig, D. Matus, S. Roth, E. Abouheif, F. Brown, C. Chiu, C. Cohen, A. Tomaso, S. Gilbert, B. Hall, A. love, D. Lyons, T. Sanger, J. Smith, C. Specht, M. Vallejo-Marin & C. Extavour. 2015. “The significance and scope of evolutionary developmental biology: a vision for the 21st century,” Evolution & Development. 17:3, 198-219.
Morris, Simon Conway. “The predictability of evolution: glimpses into a post-Darwinian world.” 2009. Naturwissenschaften. 96:1313-1337.
Noble, Denis, E. Jablonka, M. Joyner, G. Mueller & S. Omholt. 2014. “Evolution evolves: physiology returns to centre stage.” The Journal of Physiology. 11: 2237-2244.
Noble, Denis. 2015. “Evolution beyond neo-Darwinism: a new conceptual framework.” The Journal of Experimental Biology. 218: 7-13.
Pigliucci, Massimo & Gerd Mueller. 2010. Evolution, the Extended Synthesis. MIT Press.
Reid, Robert. Biological Emergences: Evolution by Natural Experiment. 2007. MIT Press.
Smith, Eric & H. Morowitz. 2016. The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere. Cambridge University Press.
Smith, John Maynard & Eörs Szathmary. 1999. The Origins of Life: From the Birth of Life to the Origin of Language. Oxford University Press.
Turner, J. Scott. 2017. Purpose and Desire: What Makes Something ‘Alive’ and Why Modern Darwinism has Failed to Explain It. New York: HarperOne.