Although it has been suggested that Aristotle all but set down a model of gene-based inheritance (Delbrück 1971), that view is strongly challenged as overly simplistic and mechanistic and attributing to DNA a much more controlling role by “posit[ing] a decidedly un-Aristotelian genetic vitalism” (Vinci and Robert 2005, p. 221). One of the most influential ideas in modern biology is epigenetics, first coined by Waddington and defined as “derived from the Greek word epigenesis, which Aristotle used for the theory that development is brought about through a series of causal interactions between the various parts” (Waddington 1956, p. 10). While no argument is being made here that Aristotle was responsible for the entire modern concept of epigenetics, Waddington considered that the Parts of Animals contributed to the development of that concept.
Further comment on Aristotle’s contributions to genetics comes from Kullmann, who sets himself “to point out some striking examples which show that Aristotle's thoughts may yet play a remarkable role in contemporary scientific discussion” (Kullman 1991, p. 137). Although most of his paper concentrates on Aristotle’s overall contributions,Footnote 12 such as his (unintended) taxonomy,Footnote 13 Kullmann makes a case for Aristotle as a proto-geneticist, even arguing that Aristotle took this role in ways that were superior to Darwin’s modelFootnote 14 because Aristotle argued that (in Kullmann’s words) “the purposeful structure of a living being depends on the programme pre-existing in the blood of the parents” (Kullman 1991, p. 146).Footnote 15
Henry discusses the question, What are the causal mechanisms behind the transmission of biological form? (Henry 2006, p. 426). He argues that the answer lies in the Generation of Animals, Book 4, where Aristotle describes the phenomenon of inheritance.Footnote 16 Aristotle maintains that there are a set of “movements”Footnote 17 that transmit the parents’ form to their offspring and that these movements “exist in the semen; potentially from remoter ancestors but in a higher degree from whatever individual is nearer.”Footnote 18
The purview of population biology includes “age structure,” and Egerton (1975, p. 307) considers that “almost all” of Aristotle’s biology was relevant to this construct. Egerton also argues that Aristotle’s History of Animals encompasses age structure in great detail, and uses the examples of mammals and birds to illustrate how Aristotle does this.Footnote 19
On Animals and Humans
Perhaps due to his experiences as a child (Shields 2012),Footnote 20 Aristotle developed a good understanding of native wildlife, exotic species, and farmed animals (Grumett 2019), and he devoted quite a lot of time to describing the care of farm animals.Footnote 21 Because he considered that animals have a soul similar to humans, and that animals’ telos is to confer their attributes and products onto their owners (for example, a cow’s milk, a sheep’s wool, a chicken’s eggs), then “a stockperson’s primary role is to promote the good of the animals in their care, ensuring that their needs, wants and desires are satisfied.”Footnote 22Footnote 23 Aristotle gave many examples of how this may be accomplished.Footnote 24
Aristotle asserted that, if a hen bird has mated with a cock and is pregnant, then if “she be trodden by another cock, the whole brood of chicks turn out like the second cock.”Footnote 25 Although this claim was said to be “very astonishing,” it has been verified (Birkhead and Møller 1998), and Brock notes that this is “another case where Aristotle’s empirical observations of biology, though apparently bizarre, have been vindicated by modern science” (Brock 2004, p. 278).Footnote 26
Gross (1995) describes how Aristotle broke from some of his predecessors such as Alcmaeon of Croton, Democritus, Anaxagoras, and Diogenes, to state that “the brain cannot be the cause of any sensations, seeing that it is itself as utterly without feeling as any of the excretions”Footnote 27 and that “it is the region of the heart that constitutes the sensory center.”Footnote 28 It has been argued that this error by Aristotle arose because of his lack of clinically-focused study and that “he never dissected a human” (Gross 1995, p. 249). Aristotle lived in an era when the budding scientific methodology did not include experimentation, which forbade him from engaging in the kind of clinically-focused research that Galen undertook six centuries later that described the function of the brain and the spinal cord (Galen 1962). However, Aristotle was active in establishing the Museum at Alexandria, where dissection was undertaken, leading to the accurate description of the human brain (Longrigg 1988).Footnote 29
Although it was published just before the search period (1970–2020), an earlier paper by Clarke and Stannard deserves mention because its authors present several arguments explaining why Aristotle reported that the brain occupied only the front of the head,Footnote 30,
Footnote 31 such as Aristotle’s desire to “create a synthesis of Pre-socratic and Platonic knowledge” (Clarke and Stannard 1963, p. 132).Footnote 32,
Footnote 33 Aristotle inaccurately described several human structures, including the cranial sutures, uterus, kidney, spleen, ribs, and heart, and “viewed biological phenomena from a philosophical standpoint,” with less attention to accuracy than is expected by biologists today (Clarke and Stannard 1963, p. 148).
Aristotle is considered by many as “the founder of comparative anatomy,” although much of his work was based upon animals (from which he generalized to humans) because he did not perform dissections of humans (Blits 1999, p. 59).Footnote 34 However, Malomo et al. describe Aristotle as having “laid the foundation of comparative anatomy and established embryology on a scientific foundation by his direct studies of the chick embryo” (Malomo et al. 2006, p. 100). These studies were detailed and undertaken by an ingenious methodFootnote 35 and influenced thinking in that field until well after the Renaissance.
Perhaps the strongest basis for the high opinion in which anatomists hold Aristotle is his focus upon function.Footnote 36 Thus Blits writes: “Form and function go together for Aristotle. Anatomy and physiology are integral components of the same science” (Blits 1999, p. 62). This position is amplified by Blits when she explains that Aristotle’s task “is to discover the principles of organization and function responsible for the various animal kinds and their relations,” which entailed Aristotle in defining the differences in form between animals and the underlying "causes" why those differences occur. Aristotle identified four causes: material, form, origin of motion (or efficient), and end (or final), and in doing so, provided a model of anatomy that went well beyond a simple description of parts, but also included the reasons for why those parts are as they are and how they might differ across species. This individual variety of animals’ form and function led Aristotle to state that “each and all will reveal to us something natural and something beautiful.”Footnote 37
In their historical article in Clinical Anatomy in 2007, Crivellato and Ribatti divert their discussion away from “many of his physiological concepts (that) turned out to be wrong” and instead focus on Aristotle’s development of a “precise topographical terminology” that cast the body into “a bipartite, symmetrical architecture,” including the front and back of the body, its top and what lay below, and its right and left sides (Crivellato and Ribatti 2007, pp. 477–479).Footnote 38 Crivellato and Ribatti’s message is clear: Aristotle set down the nomenclature for most body parts and then went on to provide detailed accounts of the anatomy of the heart, blood vessels, brain, respiratory system, digestive system, kidney and urinary tract, genitals, bones and joints, muscles, and sense organs. In doing so, “Aristotle’s contribution to the development of anatomy was enormous” (Crivellato and Ribatti 2007, p. 484), and he foreshadowed the basic principle of experimentation in modern science and developed an early the concept of an organ (organon) as an instrumental and functional part of the body (Crivellato and Ribatti 2007).Footnote 39 These ideas exerted “a sort of intellectual dictatorship on further generations of anatomists,” even to Renaissance thinkers (Crivellato and Ribatti 2007, p. 485) and William Harvey in the seventeenth century.Footnote 40 Aristotle’s ideas about ways of understanding nature, plus twelfth-century translations of the wider Greco-Arabic ancient science, have been recognized as one of the three major bases of the development of the scientific revolution during the last few centuries, along with universities and the emergence of theologian-natural philosophers (Grant 1997).
In terms of the heart, Shoja et al. (2008) remind us that Aristotle reported that it consists of three chambers.Footnote 41 In doing so, he omitted the right atrium, which he instead called a venous dilation (Shoja et al. 2008).Footnote 42 This error has been discussed at length and is attributed to the mystical tradition attached to the number three, which is probably in accordance with Plato's notion of the three corporeal faculties (mind, emotion, desire) (Lennox 2001; Van Praagh and Van Praagh 1983). Other modern scientific papers on Aristotle’s model of the heart include Shaw’s, who notes that Aristotle made “over one hundred references to cardiac anatomy and physiology” in the History of Animals and Parts of Animals and that his “main model for the heart is simple and entirely structural: the heart is a container.” (Shaw 1972, pp. 355, 385). Shaw argues that Aristotle’s model drifted away from a more modern understanding of the heart when he attempted to describe its physiology, perhaps because of the lack of adequate laboratory settings necessary to investigate the actual way the heart worked (Shaw 1972, p. 386).
In his defense against Francis Bacon’s sixteenth-century criticisms of Aristotle’s anatomical writing,Footnote 43 Cosans replicates Aristotle’s anatomical experiments by obtaining “anatomical material” from a Chicago meatpacking company (Cosans 1998, p. 311). This experience allowed him to understand the process used by Aristotle that “shows animals to consist of parts that are organized into wholes in virtue of dynamic forms” (Cosans 1998, p. 336). Cosans argues that, far from Bacon’s criticism, this kind of animal dissection “not only reveals the order within organisms but naturally led to Aristotle’s quest to understand the order amongst organisms” and thus contributed to the development of his more comprehensive philosophy (Cosans 1998, p. 336).
Frampton’s paper on the role of the heart in animal movement summarizes Aristotle’s explanation of movement as follows: “The general rule of locomotion is that there must be an unmoved mover, something that is moved, and an intermediate moved mover” (Frampton 1991, p. 310). Aristotle expanded upon this simplified model by identifying that movement is initiated by “thought and desire,”Footnote 44 and that there is “some one thing which moves” limbs, and that this is “the soul.”Footnote 45 Although apparently despite having observed that taste and touch, sight, hearing, and smell are “lodged as a rule in the head,” for Aristotle, the soul resided in the heart.Footnote 46