Aristotle, DNA, and The Unmoved Mover
This blog honors Aristotle as both the greatest of western philosophers, and as the first biologist. His work on describing the development of the chick as it passes through its many stages from embryo to hatchling is a moving demonstration of his dedication to biological science and its empirical methods. Beyond his work on embryology, Aristotle was the first scientist to identify the nature of semen as a substance containing a plan for the development of a new biological instance of its kind.
Prior to Aristotle, all of recorded Greek natural philosophy, attempting to explain the mechanism of animal reproduction, embraced the doctrine of ‘spermism’, which held that the male contributed to the future offspring the form (in the sense of structure and configuration), whereas the female contributed only the nourishment (embodied in the egg).
Pythagoras is one of the earliest thinkers credited with ideas about the origin of form in the biological production of offspring. It is said that he originated “spermism”, the doctrine that fathers contribute the essential characteristics of their offspring while mothers contribute only a material substrate. – Preformationism in Wikipedia
Distinct from spermism is the doctrine of preformationism. Many centuries after Aristotle during the Renaissance preformationism was still widely embraced; the human sperm was assumed to host a miniature version of its adult form (for humans, the homunculus, for animals, the animunculus) which developed by implanting itself in the female and simply growing by enlarging itself to the size of a newborn baby. More specifically, through the sperm, the father deposited a tiny instance of the organism representing in miniature the essential structure of the newborn. Reproduction was thus conceived as essentially a process of growth from tiny parts to larger parts. The drawing below was made by Nicolaas Hartsoeker in 1695. The implications of preformationism included the idea the homunculus must itself contain nested within it yet another homunculus. This was an attempt to account for the origin of the preformed homunculus. The argument was that homunculi must originate from homunculi, otherwise, their origin must be magical or supernatural.
Aristotle was the first to oppose the notion of the homunculus as a contradictory idea, in that it implies an infinite regress of nested homunculi. For if the homunculus is truly a miniature of the man, it must itself contain another even tinnier homunculus, and so on ad infinitum. Aristotle wrote extensively on the subject of infinity, holding that infinity can only apply to methodology or potentiality and never to actualities. (This was his famous answer to Zeno’s Paradoxes).
Rather than a preformed homunculus, Aristotle saw the sperm as containing a principle for directing the actualization or realization of the sperm’s potentiality for the creation of a new life form after its own, through the execution or unfolding of a plan, guiding its actualization from seed to new organism. Aristotle’s attempt to explain the details of the process of the realization of the ‘plan’ in the sperm, was mistaken in many ways, but his basic and absolutely original idea that the sperm carried a plan and not a miniature form of the adult was exactly right, and fundamental to his unique view of animal reproduction.
From the perspective of modern genetics, Aristotle’s key ideas regarding the nature of the ‘plan’ the notion that the plan was used to create a copy of the parent through the plan of the parent is vindicated. Modern genetics holds, however, that the plan itself is a material structure whose molecular sequences constitute ‘information’ that is used to direct the development and differentiation of the fertilized egg into the newborn organism. What is preformed, then, is not the miniature organism, but a plan for its creation from the material in which the plan is embedded.
The genetic material carries specific form, not by containing little whole animal or parents of animals, but as information that under the proper circumstances can proceed to direct the stepwise construction of the co-specific offspring; this affects the form of the offspring not by developing into any ordinary constituent part of it, but by its influence on the physio-chemical processes that bring the construction about; it is also not consumed in the process, but is passed on intact (though stored on different material parcels in distinct individuals) from generation to generation. – from Substance, Form and Psyche: an Aristotelian Metaphysics (1988), by Montgomery Furth, p. 119.
The important point here is that the genetic material (DNA), containing the plan or code for the building up of the organism, is not itself the material constituting the final form of the organism. That material is supplied through molecular biological processes, whereby the genetic material is used as a complex set of templates (conceptually analogous to a set of blueprints) to copy and finally fabricate (through various forms of RNA) the proteins that constitute the body of the organism at the level of each cell for each form of tissue.
Max Delbrück Honors Aristotle
Max Delbruck, the great 20th-century biologist, was a great admirer of Aristotle, whose unique biocentric view of the world was deeply productive, informative, and sadly forgotten by the modern science that has replaced it. Delbruck wrote, in his Nobel Lecture:
At the very beginnings of science the striking dissimilarities between the behavior of living and nonliving things became obvious. Two tendencies can be discerned in the attempts to arrive at a unified view of our world. One tendency is to use the living organism as the model system. This tendency is exemplified by Aristotle. For him, the son of a physician and the keen observer of many forms of life, it was obvious that things develop according to plans. Every animal and plant is generated in some definite way, runs through a cycle of development in which it unfolds its inherent plan, and succumbs to death and decay. For Aristotle, this very obvious feature of the world which surrounds us is the model for understanding our (sublunar) world. – from The Nobel Prize in Physiology or Medicine, Nobel Lecture, December 10, 1969
Recognizing the profound significance of Aristotle’s original idea of the sperm as carrying a plan and not a miniature replica or copy of the parent, and the direct relevance of this idea of the passing-on-of-a-plan to the modern concept of DNA, the great molecular geneticist Max Delbrück, wrote of Aristotle’s work on reproduction, the following:
Just so one should approach the study of any animal with reverence, in the certainty that any of them are natural and beautiful. I say “beautiful” because in the works of nature and precisely in them there is always a plan [emphasis added] and nothing accidental. The full realization of the plan, however, that for which a thing exists and towards which it has developed, is its essential beauty. Also one should have it clearly in mind that one is not studying an organ or a vessel for its own sake but for the sake of the functional whole. One deals with a house, not with bricks, or wood. Thus the natural scientist deals with the functional whole, not with its parts, which as separate entities have no existence. – quoted from Aristotle by Max Delbrück, in Aristotle – totle – totle, 1971
Soon after delivering that Nobel lecture, Max Delbrück, in 1971, wrote a paper in homage to Aristotle’s brilliant theory, entitled ‘Aristotle – totle – totle‘ (and later in a personal letter to a dear relative with the title: “How Aristotle Discovered DNA.”), recommended that Aristotle be awarded the Nobel prize in biology for his discovery of the principle underlying DNA, i.e., a plan as the causal principle for the creation of a new organism. Thus the plan is used to guide the future development of the newborn, but is itself unchanged in the process. Delbrück argued that it is from his work on embryology that Aristotle first came to the insight of ‘the unmoved mover’, which he later applied to physics and cosmology. On the idea of the unmoved mover, Delbrück wrote:
I should like to suggest, furthermore, that the reason for the lack of appreciation, among scientists, of Aristotle’s scheme lies in our having been blinded for 300 years by the Newtonian view of the world. So much so, that anybody who held that the mover had to be in contact with the moved and talked about an “unmoved mover” collided head-on with Newton’s dictum: Action equals reaction. Any statement in conflict with this axiom of Newtonian dynamics could only appear to be muddled nonsense, a left over from a benighted, prescientific past. And yet, “unmoved mover’ perfectly describes DNA: it acts, creates form and development and is not changed in the process. – Max Delbrück, ‘Aristotle–totle–totle‘ , Reprinted from “Of Microbes and Life” J. Monod and E. Borek, eds. Columbia University Press, 1971, p. 55.
Cellular Dynamics not Reducible to Physics
Biogenesis, the development of entire organisms from strands of DNA containing the ‘plans’ for all possible protein molecules needed to create and to continuously sustain the life of a given species, is a dramatic case of emergence. Life cannot be reduced to the molecular properties of DNA alone. What is needed is to explain the dynamics of biogenesis and the incredibly intricate coordination and synchronization of complex activities within each individual living cell that bring about the emergence and maintenance of life itself. For a dramatic presentation of the profound complexity, and intricate orchestration of life processes within each of the 120 trillion cells in each of our bodies, view the 7-part series: Secret Universe The Hidden Life of the Cell.
Organisms versus Machines
Living organisms are not machines, they are both the self-referencing manifestation and product of the uniquely biological process called metabolism. The organism is wholly a metabolizing system and at the same time the continuous product of that same metabolizing system. In The Phenomenon of Life: Toward a Philosophical Biology Hans Jonas teaches us the contradiction of regarding this metabolizing system as a machine:
Metabolism thus is the constant becoming of the machine itself — and this becoming itself is a performance of the machine: but for such performance there is no analogue in the world of machines. [page 76]
What makes metabolism so remarkable and ontologically unique, it that the resulting form, the living organism, exists independently of its constituent matter, for this matter is dynamically undergoing replacement while the form remains constant (or invariant):
The basic freedom of organism was found to consist in a certain independence of form with respect to its own matter. According to a strictly material world-account such independence is either an absurdity or a deceptive appearance. Its emergence with emerging life indeed marks an ontological revolution in the history of “matter”; [page 81]
DNA, Blueprints, Encoded Copying, and Perception
Aristotle seems to have anticipated and articulated the idea that a plan is a form of an object in the sense that each relevant property of the object (each element that is of interest to the ‘copier), is represented structurally in the plan. This approach, it has been argued, is intended by Aristotle when he argues that perceptions are ‘like’ copies of their object without taking in their matter. Thus they are formally like their objects. They resemble their objects with respect to their formal encoding of those objects. Discussing Aristotle’s theory of perception, one student of Aristotle writes:
On one alternative approach, which may be called the intentionalist interpretation, the sense organs become like their objects without actually coming to exemplify the sensible qualities perceived. Instead, they become like them by coming to symbolize them in one way or another. In its simplest form, this approach regards the likeness involved in perception as akin to the likeness obtaining between a house and its blue print. If an architect has three blue prints on her desk, one of a house, one of a church, and one of a factory, then exactly one of them has the same structure as the house built according to its specifications. She may say with all linguistic propriety, when pointing to one set of the blueprints, ‘This one is a house.’ That set of blue prints ‘is a house’ not because it exemplifies the property of being a house, but because it somehow encodes that property. So, to begin, two things can be like each other with respect to the same property without their both exemplifying that property. As applied to Aristotle’s theory of perception, then, a sensory organ can be made like its object, can receive its sensible property, without actually exemplifying that property. – from Controversies Surrounding Aristotle’s Theory of Perception by Christopher Shields in Stanford Encyclopedia of Philosophy
Aristotle: Plans as the Mechanisms for Likeness
Here then we see two examples of Aristotle thinking in terms of plans as the vehicle for transmitting likeness: one of life and one of perception. I suggest that this mode of grasping complex life processes was entirely unique to Aristotle and has been appreciated by his modern interpreters. We have already seen how Aristotle’s idea of reproduction being the product of a biological plan transmitted from parent to child (at both the organismic level of child breeding and at the cellular level of cell reproduction through mitosis, which we now know is DNA).
What has never (to my knowledge) been discussed is the intriguing relationship between Aristotle’s use of (attention-driven, a la Brentano) encoding of object attributes into perceptual forms. The connection that I have in mind is that suggested by The Perception of a Permanent World by J. J. Gibson, Cornell University, that the features of perception are psychophysically dynamically mapped to the encoded invariance of energy gradients such that the dynamic invariants under transformation of these energy gradients, when detected by the sensory system yield the direct perception of the existence and properties of the object.
I would argue further that it is only in this sense and not in the Lockean sense that sensory qualities are copies of their object qualities. I would also note that the DNA plan is static while the sensory encoding mechanism and process is fully dynamic, thus, unlike DNA, the sensory encoding is not ‘left behind as a repository’ but is constantly being updated in real-time, and never stored, because, as J. J. Gibson pointed out in The Senses Considered as Perceptual Systems, ‘it is always out there to look at.’ This is why Aristotle’s realist theory of perception, extended, in by view, by Gibson’s realist theory, by requiring dynamic changing encoding of environmental features (including environmentally existing objects, of course), do not require (and in fact deny) any representational theory to account for the encoded dynamic structures whose detection by the perceptual system causes the direct experience of the object and object properties that they encode.
References (in the order cited)
- Preformationism in Wikipedia
- Furth, Montgomery, Substance, Form and Psyche: an Aristotelian Metaphysics, Cambridge University Press, New York, 1988.
- Delbrück, Max, The Nobel Prize in Physiology or Medicine, Nobel Lecture, December 10, 1969
- Delbrück, Max, Aristotle – totle – totle, 1971.
The Hidden Life of the Cell, Daily Motion, May 1, 2013.
- Jonas, Hans, The Phenomenon of Life: Toward a Philosophical Biology , Harper & Row; 1st edition (1966)
- Shields , Christopher Controversies Surrounding Aristotle’s Theory of Perception, Stanford Encyclopedia of Philosophy, 2016.
- Gibson, James J. The Perception of a Permanent World Cornell University, November 1969.
- Gibson, James J. The Senses Considered as Perceptual Systems, Allen & Unwin, May 1968.
Copyright © 2014 by bioperipatetic.
Published on April 19, 2014 @ ,3:55 pm
Latest revision: May 15, 2019 @ 6:07 pm