This Dialogue has proved very interesting and I appreciate both the invitation from TheBestSchools.org to take part, and the intelligent and courteous way in which it has been conducted, both by the moderator (who was also the interviewer) and by Professor Wilson. I also appreciate some boof the criticism of my position in the latter’s Response and his suggestions for further reading.
In this final contribution I will not attempt to answer all the questions that arise. I will focus my remarks on what I see as the central issues on which to sum up my reactions to the Dialogue as a whole.
A.Can neo-Darwinism be redefined as Tinbergen’s “four questions”?
1. Neo-Darwinism as originally defined by Weismann and Wallace was a specific theory of evolution, capable of empirical falsification.
Neo-Darwinism as defined by its nineteenth-century founders, August Weismann and Alfred Russel Wallace (right), was an experimentally testable theory of evolution. Tinbergen’s “four questions” do not express the specific empirical predictions of neo-Darwinism and, as questions, they are not empirically testable. If neo-Darwinism is to be redefined as Tinbergen’s four questions, as Wilson proposes, then it would no longer be a theory of evolution and therefore would not be what neo-Darwinism was about when it was formulated.
That theory has been falsified. It also seems to me that Wilson agrees that this is the case, when he says in his Statement:
Anything that smelled of directed evolution was branded with the label “Lamarckian” and declared impossible, much as group selection was declared impossible during the 1960s and ’70s. Backing away from this dogmatic position is an important part of the Extended Evolutionary Synthesis.
2. What can questions do?
Questions might imply theories, and even be theories masquerading as questions, for example when the questions are rhetorical. But Tinbergen’s four questions are clearly not rhetorical. Nor do they form a specific theory of evolution. As I argued in my Response, instead they form a valid framework within which specific theories can be developed.
They are based on Aristotle’s “four causes,” on which I elaborate in Dance to the Tune of Life. I show there that the four causes require extension to include attractors, coding, and reasons, but I don’t see those extensions as fundamental. An attractor can be seen as an evolved final cause, coding can be seen as a formal cause, and reasons can also be seen as a final cause.
As a framework for research, I therefore agree with Wilson that Tinbergen’s four questions are sufficient.
3. How does neo-Darwinism differ from Darwinism?
Neo-Darwinism was formulated by Weismann and Wallace explicitly to correct what they thought was the incorrect acceptance of the inheritance of acquired characteristics in Darwin’s work. If neo-Darwinism is now to be redefined as accepting the inheritance of acquired characteristics, then we no longer have the original reason for distinguishing it from Darwinism.
Modern theories of evolution can then be seen as deriving from Darwinism, rather than from neo-Darwinism. It seems to me that the time has come to drop the prefix “neo-.” Following the lead of Waddington, I am perfectly happy with describing my view of evolutionary biology as originating with Darwin (and with Lamarck), but I don’t see it as originating with neo-Darwinism.
4. What do people generally understand by neo-Darwinism?
Professional philosophers of science, popularizers of science, and the public at large naturally and almost universally understand this to be the original definition of neo-Darwinism.
It is impossible to read, for example, the recent book Mind and Cosmos by the distinguished philosopher Thomas Nagel (right) as a philosophical attack on Tinbergen’s four questions. He doesn’t even refer to Tinbergen. The book is clearly a sustained and fundamental attack on original neo-Darwinist theory as formulated by Weismann and Wallace and subsequently developed into the Modern Synthesis.
Similarly, Mary Midgley’s articles and books criticizing neo-Darwinism, in response to The Selfish Gene, also clearly deal with the original theory, not Tinbergen’s four questions, which are not even referenced.
As another example, John Dupré in his excellent book, The Disorder of Things, is very critical of the neo-Darwinist perspective (although not by name), but I suspect that he would be happy enough with Tinbergen’s four questions.
Lamarck, probably the greatest biologist in history, turned that ladder of explanation (starting with the supreme mind, followed by man and then down to the infusoria) upside down. He was the man who said that it starts with the infusoria and that there were changes leading up to man. His turning the taxonomy upside down is one of the most astonishing feats that has ever occurred. It was the equivalent in biology of the Copernican revolution in astronomy.
This could not possibly have been written from a neo-Darwinist perspective. Lamarck was the bête noire of neo-Darwinism. Bateson (right) knew of Tinbergen’s work, but does not refer to or criticize the four questions.
In fact, looking through my own collection of books and articles that discuss neo-Darwinism, I simply can’t find any that criticize the four questions.
5. Does it matter?
I remain puzzled by what I see as a completely new definition of neo-Darwinism. I am therefore forced to conclude that Professor Wilson must see the original definition of neo-Darwinism as no longer tenable.
As he says himself in his Statement, the hypothesis of the Weismann Barrier has been demonstrated to be wrong:
Rigid adherence to Weismann’s doctrine should be declared thoroughly obsolete, along with rigid rejection of group selection.
The implications of this development are too important to be subsumed into a new definition carrying the name of “neo-Darwinist” theory since they contradict the original, and usual, version of that theory.
Moreover, they contradict it in ways that fundamentally change our view of the nature of living organisms. I enlarge on this point in section C.
B.Evolution itself evolves.
The key difference between hard-line neo-Darwinism and the position that both Wilson and I favor, albeit in somewhat different ways, is whether the evolutionary process is directed.
Wilson writes in his Statement:
Since James Mark Baldwin . . ., we have known that directed behaviors that are a product of undirected evolution can double back to influence the evolutionary process. What the organism chooses to do by learning alters the selection pressures operating on the genes of the organism. This was celebrated as a major insight at the time — a form of directed evolution that was fully consistent with Weismann’s doctrine . . .
I agree with the majority of this statement, although, following Patrick Bateson (right), I prefer to give the credit to Douglas Spalding (1841–1877), who had the idea before Baldwin.
As I have already explained in this Dialogue, the part of this quotation that I don’t understand is the idea of consistency with Weismann’s doctrine. I cannot see how directed evolution could be consistent with Weismann’s ideas of everything being generated by blind chance.
There is a deep misunderstanding about the role of blind chance in evolution. As any good physicist will tell you, stochasticity at low (e.g., molecular) levels is perfectly consistent with order at higher levels, as for example described by thermodynamics. Everything, including organisms, must live with the existence of stochasticity at low levels. Organisms must therefore harness stochasticity to generate functionality. It is functionality — and its ability to constrain what happens at lower levels — that is a necessary prerequisite of directed evolutionary change.
Blind chance was therefore necessarily involved in the evolution of processes that enable directed evolution. The evolution of cells in the immune system in response to challenges from new antigens illustrates one of the main processes involved. Faced with a new antigen challenge, the mutation rate in the variable part of the genome can be accelerated by as much as one million times. So far as we know, those rapid mutations occur randomly. If we focus our attention on just that part of the genome, the process will appear to be neo-Darwinian. But the location in the genome is certainly not random. If such a high rate of random mutations were to occur throughout the genome the organism would almost certainly not survive. Necessary functionality in the fixed parts of the proteins involved would be lost. The functionality in this case therefore lies precisely in the targeting of mutation at the relevant (variable) part of the genome and the preservation of the fixed part. The mechanism is directed, because the binding of the antigen to cell receptors in the secondary lymphoid organs (spleen and lymph nodes) itself activates the proliferation process. Organisms can therefore respond to environmental challenges by rapidly and selectively mutating just parts of their genomes. In so doing, they use targeted stochasticity to achieve the goal.
This example shows that the process can occur in the lifetime of an individual organism. There is no reason why this kind of mechanism should not be used in evolutionary change, and it is.
A well-known, functionally driven form of genome change is the response to starvation in bacteria. Starvation can increase the targeted reorganizations of the genome by five orders of magnitude, i.e., by a factor of over 100,000. Again, the location of the mutations is targeted. This is one of the mechanisms by which bacteria can evolve very rapidly and in a functional way in response to environmental stress by triggering rapid mutation in selected parts of the genome without disturbing the rest.
These hypermutation mechanisms have been investigated by Richard Moxon and his colleagues who use the term “contingency locus” to characterize the targeted loci of hypermutable DNA. Since “mutation rates vary significantly at different locations within the genome,” they propose that “it is precisely in the details of these differences and how they are distributed that major contributions to fitness are determined.” In an earlier article, Moxon and Thaler write:
This phenotypic variation, which is stochastic with respect to the timing of switching but has a programmed genomic location, allows a large repertoire of phenotypic solutions to be explored, while minimizing deleterious effects on fitness.[emphasis added]
I have emphasized the last phrase because it is the key to understanding such goal-directed processes in organisms. What is random (blind chance) when one considers the generation in time in the hypermutation regions is consistent with directed evolution when one considers the spatial targeting of the activation of hypermutation.
So, blind chance and natural selection may well have been sufficient to allow the emergence of directed hypermutation. But once it has done so, evolution itself evolves. There is a kind of bootstrapping here. There is no going back. Organisms that have directed, functionally significant hypermutation will clearly win out and will pass that ability on to subsequent generations.
Evolution is not therefore a single parsimonious process. There have been many such bootstrappings, each of which changes the subsequent evolutionary process by adding new directional mechanisms to the armory of mechanisms used by nature. The neo-Darwinist mechanism itself is also in this category. Before the evolution of multicellularity, the Weismann Barrier could not and did not need to exist. And when it did arise, nature found ways of circumventing it so that it is a relative rather than an absolute barrier.
So was the watchmaker really blind? This is not now as easy a question as it may have seemed when Richard Dawkins wrote The Blind Watchmaker. The mechanisms that underpin directed evolution have evolved. Having done so, the genie cannot be put back into the bottle. Perhaps we should say that the Watchmaker may have started off blind, but she has become one-eyed. Subsequent evolution is not pure chance. The implications of that change in view are profound, as I lay out in the final section.
The existence of directed evolution is the key. And I believe that both Wilson and I see it as such, although we may have different ways of spelling out the implications. He sees it as another extension of what he chooses to call neo-Darwinism.
My view is that there could not be a more important difference between the neo-Darwinist Modern Synthesis as usually defined and the new trends in evolutionary biology leading towards the acceptance of forms of directed evolution. Whether we see the world as governed by pure chance or at least partially by directed change is fundamental to the humanities and social sciences at least as much as (if not more than) to physics, chemistry, biology, and engineering.
Many in the humanities and social sciences view the original and dogmatic forms of neo-Darwinism — restricting evolutionary change to blind chance and natural selection — with at least suspicion and sometimes with outright hostility. The humanities in particular find it much more conducive to think that there is genuine purpose. Mere belief or wishful thinking are not valid reasons of course for ignoring whatever scientific investigation tells us, if that really is that there is no purpose. But it is nevertheless obvious that a version of evolutionary biology that includes directed change is of more than casual interest. And if Wilson and I are right that there is directed evolution, then it is important to the humanities and social sciences to make this absolutely clear. It is a fundamental change in evolutionary biology.
Moreover, the social science and humanities implications do not really depend on whether directed evolution originally arose from purely chance events or whether it should be viewed as an inevitable feature of the universe. Once directed evolution has emerged it takes over, just as an attractor takes over once it has formed in complex systems.
This property of attractors is not just a property of biological systems. The air molecules of a tornado obey the same physicochemical equations as other air molecules, but once they are drawn into the tornado, they also conform to the high-level dynamics of the tornado. So, to take an example at a vastly bigger scale, do the particles, planets, stars, and other components of a rotating spiral galaxy. Similarly, at a micro-scale, the channel proteins, membrane lipids, and charged ions in heart cells obey the standard laws of chemistry, but are also constrained to behave as a coordinated ensemble when generating the electrical rhythm of the heart.
How this can happen is explained by the mathematics of Biological Relativity. There is nothing fuzzy or mystical about the forms of causation involved. They can be represented rigorously in mathematical form. For those who know enough mathematics to appreciate the point, the constraints of the components by the whole enter into the solutions of the differential and related equations by determining the initial and boundary conditions that are essential for there to be particular solutions of the equations.
If the reader finds any of these ideas interesting, even exciting, there is much more on the same theme in Dance to the Tune of Life.
1. As an example, Richard Dawkins’s question to Lynn Margulis in their 2009 debate is clearly rhetorical: “It [Neo-Darwinism] is highly plausible, it’s economical, it is parsimonious, why on earth would you want to drag in symbiogenesis when it’s such an unparsimonious uneconomical [theory]?” Margulis’s reply was simply, “Because it’s there.” (See D. Noble, Dance to the Tune of Life: Biological Relativity, Cambridge: Cambridge University Press, 2017; p 138.)
2. D. Noble, Dance to the Tune of Life: Biological Relativity. Cambridge: Cambridge University Press, 2017; pp. 176–181.
3. C.H. Waddington, The Strategy of the Genes: A Discussion of Some Aspects of Theoretical Biology. London: Routledge, 2014. (Originally published in 1957.)
4. T. Nagel, Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature is Almost Certainly False. Oxford: Oxford University Press, 2012.
6. J. Dupré, The Disorder of Things: Metaphysical Foundations of the Disunity of Science. Cambridge, MA: Harvard University Press, 1993.
7. G. Bateson, Steps to an Ecology of Mind. Chicago: University of Chicago Press, 1972; p. 433.
8. See ibid., p. 181.
9. P. Bateson, “The Adaptability Driver: Links between Behavior and Evolution,” Biological Theory, 2006, 1: 342–345.
10. This was the main point of my lecture at the Physiological Society on 21 November, 2016 (which was a longer version of the lecture given at the recent Discussion Meeting of the Royal Society and the British Academy, 7–9 November, 2016).
11. R. Moxon, C. Bayliss, and D. Hood, “Bacterial contingency loci: the role of simple sequence DNA repeats in bacterial adaptation,” Annual Review of Genetics, 2006, 40: 307–33.
12. E.R. Moxon and D.S. Thaler, “The tinkerer’s evolving tool-box,” Nature, 1997, 387: 659–62.
13. “Evolution evolves” is the title of a focused issue of the Journal of Physiology devoted to physiology and evolution: Journal of Physiology, 2014, 592: i–iv, 2237–2438.
14. R. Dawkins, The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design. New York: Norton, 1986.
15. I am indebted to the philosopher Sir Anthony Kenny for suggesting this expression for treating the Blind Watchmaker issue in the light of new trends in evolutionary biology.
16. Some cosmologists consider that the fine tuning of the cosmological constants might suggest that much of what has emerged during the evolution of the universe and of life may be an inevitable consequence of the fine-tuning, however that came about. To avoid this conclusion some cosmologists propose the existence of multiple universes, or a “multiverse,” but at this stage in our knowledge that can best be described as pure metaphysical speculation. It is hard to see how any empirical test of the “multiverse” hypothesis could be formulated, let alone performed.
17. D. Noble, Dance to the Tune of Life: Biological Relativity. Cambridge: Cambridge University Press, 2016; Chapter 6.
18. Ibid.; Chapters 7–9.