Written by Alex Pinsk

1§1 “[A] phlegmatic person [may] be born of a phlegmatic” according to Hippocrates who made this first revolutionary observation of its kind. Heredity is understood in greater detail today than it ever has been in the past; however, rarely is its timeline traced back to its primary origins. Medical theories changed and developed throughout the Classical Era as new views and perspectives emerged. New discoveries advanced science and brought in new ideas, causing various concepts and definitions to undergo significant shifts. There is a clear progression of medical thought throughout history, forming a timeline that can be traced back to the Pre-Socratics who developed the first definitions of genetic concepts. As society advances and new technologies emerge, theories surrounding heredity and inheritance also develop. Throughout this paper, I will explore the concept of genetics as defined by Democritus, Empedocles, Hippocrates, Plato, Aristotle, Theophrastus, and Galen—discussing their personal beliefs and the ways in which their thoughts influenced each other.

1§2 When discussing the progression of the concept of genetics, it is important to recognize the pertinence of rationality and methodological reasoning. Many ancient theorists and doctors looked to organization and classification for the purpose of making sense of science and of the world around them. Most early theories came in the form of comparisons and analogies used to explain environmental and medical problems. The “guess and test” method was commonly used in order to explain, complicate, or treat an issue because many people were starting from scratch when testing their theories. Additionally, many of these philosophers challenged the ideas of their predecessors and contemporaries in order to shift the premises of existing views or to develop new theories  based upon changing intellectual thought, new “data” and new discoveries. The idea of heredity, specifically, was a new concept which required serious thought and examination for those exploring genetics as well as eugenics.

1§3 One initial major figure who influenced the study of genetics was Democritus (460-370 BCE)[1]. Democritus was a physicist and the “founder of atomism” (Mayr 86). He researched the building and forming of structures as they related to science. He thought that there was an inevitable order and certain mechanism that made up all things. Democritus provided the key to the development of the concept of heredity by pioneering the idea that there was a science involved with human creation.  Was it possible that there were specific objects or occurrences that fit together in order to create everything, including humans?  The idea that human creation might be explained by concrete facts rather than divine intervention was novel and likely provided the impetus for further thinking on heredity. Thus, Democritus lay the groundwork for his successors to formulate ideas within these atomist theories and to ultimately form a developing definition of heredity.

1§4 Another major philosopher, Empedocles (490-430 BCE), also influenced the idea of genetics. Empedocles followed the ancient atomists’ theory that “life could be explained using basic concepts from physics” (Everson 4). However, Empedocles thought that “attraction (love)” and “repulsion (hate)” also played a key role. Essentially, Empedocles envisioned that various pieces of matter randomly attached in order to form different objects, body parts, and other cohesive (or non-cohesive) figures. Only a few of these formations are strong enough and sufficiently-structured to survive and to reproduce (Everson 4). While he did not specifically discuss genetics, Empedocles mentioned the idea of offspring coming from live beings, implying that pieces of matter coming from live beings might create another live being. Thus, the concept of heredity—of passing down traits or matter from one life form to another—is developed further.

1§5 The idea of heredity further evolves with Hippocrates (460-375 BCE). In fact, he uses the word hereditary in order to discuss the relationship between parent and offspring. Hippocrates, in Section 5 of On the Sacred Disease, explains that:

“origin is hereditary, like that of other diseases. For if a phlegmatic person be

born of a phlegmatic, and a bilious of a bilious, and a phthisical of a phthisical,

and one having a spleen disease, of another having disease of the spleen, what

is to hinder it from happening that where the father and mother were subject to

this disease, certain of their offspring should be so affected also…”

This passage is vital to understanding the process of development of genetic theory overtime in that it clearly suggests that children acquire traits from their parents. If a parent is “bilious” or has a “spleen disease,” it is possible and often likely that the child of that parent would be susceptible to those same conditions. While Empedocles discusses the idea of reproduction and of the forming of matter, Hippocrates emphasizes the passing down of traits from one person to another.

1§6 During the time of the pre-Socratics, many people in ancient Greece and Rome from all walks of life—common people, slaves, royalty—believed to some degree in the influence of deities in everyday life. They believed that gods controlled various aspects of life and had authority over people and fate. However, starting around the time of Plato (428-348 BCE), philosophers began to think that perhaps gods were not the sole governing forces in their lives. They considered that “the world…life, or specific organisms, [were] not the products of the action of a god, as was universally believed in the prephilosophical period” (Mayr 303). As people—or at least philosophers and theorists—began to consider the possibility that gods were not the cause of everything, there was more room for scientific, logical thinking. People, rather than merely gods, seemed to have some effect on the outcome of situations—by means of medicine, they could successfully treat certain diseases and illnesses. Thus, studying the workings of the human body became more of a priority. There was a greater understanding of order and of planning, and factual information became more valuable and viable. This new way of looking at things—with an arguably more rational perspective—was a major influence and ultimately formed new theories regarding the study of heredity. If the gods were not always in complete control and people could be saved using medicine, then doctors needed to know about the workings of the human body, and to develop theories about the origin of disease.  In order to do this, some understanding of genetics or heredity became increasingly important.

1§7 With this new mindset, Plato discusses the idea of conception, exploring the idea of the womb and how it relates to genetics. While Plato is more focused on geometry than anything else, he does provide theories which explore conception, an inevitable subset of the concept of heredity. Specifically, Plato explains in Section 91 of the Timaeus that males “sow in the womb, as in a field, animals unseen by reason of their smallness.”[2] In other words, men do have an influence on the children that they produce because they sow the seeds in the womb. The idea of men physically implanting something inside a woman demonstrates Plato’s knowledge that a piece of the father lays inside the child. While “it is not clear that he believes that the female contributes seed to the formation of the embryo” (Preus 67), evidently, Plato understands that the man plays a key role. This represents another step forward in the development of the theory of heredity.

1§8 While genetics and the concept of heredity are both major subjects of research for Plato, he also references the idea of eugenics. Eugenics, the idea of passing down only the best traits in order to maintain characteristics of the highest standard, has been a major subject for many doctors and theorists throughout time. Plato is one of the first to mention this concept in his Republic. He “depicts a society where efforts are undertaken to improve human beings through selective breeding” (Wilson). While he does not describe the science behind heredity or the concept of genetic theory, Plato does reference the passing-down of traits, namely here, the best traits. This is significant in the timeline of the definition of genetics because it establishes a subsection of heredity. Not only did Plato study conception, but he also studied eugenics.

1§9 While Plato’s theories do not demonstrate knowledge of a woman’s role—regarding heredity—in conception, Aristotle (384-322 BCE) builds on Plato’s theory and does, in fact, provide an explanation for the role of the female. Aristotle not only believes that  “‘the seed is generated by the male, and the female provides the place’” (Preus 67), but also believes that both men and women have different fluids that mix together during conception. He explains in On Generation and Corruption[3] that both the female and the male pass traits down, i.e. there are pieces of both the mother and father in the resulting offspring. Evidently building on theories of philosophers before him, Aristotle adds various aspects to the concept of genetics. Of supreme importance is the idea of a seed. Aristotle explores the fact that there is something inserted into a woman that does what a seed does, i.e. grows and develops. Additionally, “Aristotle also [points] out that peculiarities of hair and nails, and even of gait and other habits of movement, may reappear in offspring,” going on to say that, “[c]haracters not yet present in an individual may also be inherited—such things as gray hair or type of beard from a young father—even before his beard or grayness develops” (Sturtevant 1). The notion that children physically acquire these traits from parents is new in that Aristotle notices the physical appearance of the parent and is able to relate it to that of the offspring. Habits and identities associated with the mother or father are, too, associated with the offspring, expanding further on genetics in ancient times.

1§10 Many philosophers examined genetics with regard to the human body; however, Theophrastus (372-287 BCE) was more interested in plant genetics. Theophrastus spends much of his time discussing properties and environments of various plants and animals in his works. In his History of Plants,[4] Theophrastus discusses flowers, classifying them as “male” and “female.” He makes the claim that a female flower is only able to grow and ripen with the aid of a male flower. Again, the idea that it takes two to produce an offspring—be it an animal or a plant—is evident. Theophrastus studied under both Plato and Aristotle, applying their ideas to his own research on plants. While Theophrastus investigated plants rather than people, many of his ideas relate to heredity as it is understood with regard to human beings. Namely the application of his theories onto human beings is significant.

1§11 Furthermore, Galen, who lived significantly after those of the above philosophers (129-216 CE), is credited with studying resemblance and the female role in conception. Specifically, in On Seed,[5] Galen discusses and elaborates on Aristotle’s ideas, expressing that women do have an influence on the offspring, i.e., they also produce a seed. Galen specifically discusses the fact that children look like their parents—sometimes like their mother and sometimes like their father—thus, deducing that it is not solely one parent who passes down traits to a child. The idea of physical appearance is interesting to Galen as it was to Aristotle. As it happens, Galen utilizes considers many of Aristotle’s theories in order to draw both parallels and contradictions to his own theories and ways of thinking. Galen was not one to look to his contemporaries when studying medicine. He examined the work of Aristotle, Hippocrates, Plato, and the Alexandrians in order to develop his medical theories. Often starting with these already established thoughts gives a theorist room to belie and adapt these ideas into his own.

1§12 Galen is not the only one who adjusted his theories based upon those of his predecessors. All of these philosophers build on each other’s ideas in light of new information, data or intellectual thought in order to establish novel, often more accurate theories, just as many researchers and philosophers do today. It is beneficial to begin work by considering what others have previously explored in order to advance theories; this is important even if just to contradict their ideas. It is evident here that over a few-hundred-years these renowned ancient figures were able to come up with a variety of approaches to medicine and to the concepts of heredity and genetics specifically. These ideas are still—although more comprehensively—understood and used today.

1§13 Many people attribute scientific discoveries to theorists and researchers of the nineteenth and twentieth centuries. However, it appears that the groundwork for a significant scope of medical thought came even before the third century. As the ancient philosophers studied the work of their predecessors, it is important that we do the same and realize the contributions to the concept of heredity made in the first century.


[1] All dates throughout paper pulled from Encyclopedia Britannica (2017)

[2] Referenced by Preus in Galen’s Criticism of Aristotle’s Conception Theory

[3] Aristotle, On Generation and Corruption

[4] Theophrastus, History of Plants

[5] Galen, On Seed


Encyclopedia Britannica, Encyclopædia Britannica, Inc., 2017.

Everson, Ted. “Ancient and Medieval Inheritance .” The Gene, Greenwood, 2007, pp. 1–9. Print.

Galen. “The Capacities of the Soul.” Galen: Psychological Writings, edited by P. N. Singer and Piero Tassinari. translated by Vivian Nutton and Daniel Davies, Cambridge University 2013, pp. 374–409.

Hippocrates, and Heraclitus. “Nature of Man.” Hippocrates. On the Universe, translated by W. H. S. Jones, IV, Harvard University Press, 1992, pp. 1–41.

Hippocrates, et al. “On the Sacred Disease.” Hippocratic Writings; and On the Natural                                          Faculties, Encyclopedia Britannica, 1955, pp. 1–11.

Longrigg, James. Greek Medicine: from the Heroic to the Hellenistic Age; a Source Book.                                    Duckworth, 1998. Print.

Mayr, Ernst. “Origins Without Evolution.” The Growth of Biological Thought: Diversity,                                       Evolution, and Inheritance, Belknap, 1982, pp. 301–309. Print.

Preus, Anthony. “Galen’s Criticism of Aristotle’s Conception Theory.” Springer, vol. 10, no. 1, pp. 66–85. JSTOR.

Sturtevant, A. H. “Before Mendel.” A History of Genetics, Cold Spring Harbor, 2001, pp. 1– 2. Print.

Wilson, Philip K. “Eugenics.” Encyclopedia Britannica, Encyclopædia Britannica, Inc., 2017.