Genes and Morality in Ancient Rome

Richard Hutchins

In the past decade, humanities scholars have increasingly sought to explain human society, psychology, and morality in terms of genetics and evolutionary history. How many times have you been talking with a friend or family member about an important issue – such as whether humans are fundamentally cooperative or selfish, hierarchical or egalitarian, aggressive or compassionate – only to hear about the ‘selfish gene’, the ‘god gene’, ‘primate harems’, or, more recently, lobsters!

There exists a long history of attempts to explain human nature in terms of natural, deterministic forces. If one had to locate an early, influential source, one might pick up the Hippocratic treatise Airs, Waters, Places, with its notion that social behavior, political structures, race, and ethnicity, are best explained in terms of the natural environment from which they emerge.

In the twentieth century, authoritarian and fascist movements tried to create national identities based on deterministic, pseudo-scientific views of race and ethnicity. While fields like neuro- and cognitive science have expanded our knowledge of the mind, one may still be reasonably suspicious of recent attempts to reduce the human mind and society to biological forces.

Bust of Epicurus (341–270 BC), founder of the philosophical school that bears his name – Epicureanism; Roman copy after a lost Hellenistic original (British Museum, London).

One of Rome’s greatest thinkers about the influence of the environment on human behavior was Titus Carus Lucretius. Living approximately from 94 to 55 BC, in the waning days of the Roman Republic, Lucretius was a scientist, poet, and Epicurean philosopher. In fact, he is our fullest source for the idea of atomism in Classical antiquity.[1]

In his only surviving work, the six-book poem De rerum natura, or On the Nature of Things, Lucretius argues that the world was not designed by gods but resulted from the chance collision of atoms. Lucretius also describes how humans and animals evolved from earlier versions of their species through competition and cooperation. The main argument of De rerum natura is that by living according to nature one can achieve, in this life, a state of tranquillitas, or inner peace, worthy of the gods. But much less well known is that Lucretius was an ancient forerunner of modern theories of genetics and even DNA.

The opening of Lucretius’ poem, as preserved in a 15th-century manuscript (Vatican Library Lat. 1569, 1r). The first line of poetry begins with the cherubic A and descends down the inscription-like capitals, before the second line appears on the cherub-suspended parchment. (Lucretius would be either amused or bemused by the composition.)

In Book Four of De rerum natura, Lucretius describes how the atoms in the “seeds” (semina) of parents cause hereditary resemblances in their children. While Lucretius of course does not use the word “genetics” or recognize the concept of DNA as it is understood today, he does think that children inherit traits from their parents, grandparents, and even great-grandparents. What features the child will have depend on whose seeds “conquer”, “master”, or “predominate” during sex and the reproductive process (4.1209–17).

et commiscendo cum semine forte virili
femina vim vicit subita vi corripuitque,
tum similes matrum materno semine fiunt,
ut patribus patrio. sed quos utriusque figurae
esse vides, iuxtim miscentes vulta parentum,
corpore de patrio et materno sanguine crescunt,
semina cum Veneris stimulis excita per artus
obvia conflixit conspirans mutuus ardor,
et neque utrum superavit eorum nec superatumst.

And in the mixing together of seed (commiscendo… semine), when by chance the woman has suddenly conquered the male force by her force and has mastered it (i.e. in sex), then [children] are born resembling their mothers because of the [predominance] of the mother’s seed, just as [children are born resembling the] fathers because of the [predominance of the] fathers’ [seed]. But those whom you see resembling both parents, mixing the features of their parents together, grow both from their father’s body and their mother’s blood, when mutual heat and two breathing as one face to face has dashed together the seeds (semina… conflixit) that have been stirred up in the limbs by the goads.[2]

Lucretius goes on in this passage to argue that children may even resemble their grandparents or great-grandparents. This is because “the parents often conceal in their bodies many seeds mingled in many ways.” Earlier generations “hand down” (tradunt) seeds to the parents, and sometimes these older seeds predominate over those of the immediate parents. So, while Lucretius does not have the terminology of contemporary genetics or the full-scale concept of the human genome, he does think that atomic structures in the seeds of parents battle it out during sex and the reproductive process to determine what the child will look like and what capabilities it will have.

A Roman gamboling piglet, the animal considered by Epicureans as a kind of mascot, 1st century BC/1st century AD (found in the Villa dei Papyri, Herculaneum, now in the Museo Archeologico Nazionale, Naples, Italy.)

Lucretius also thinks that animals pass on features from parents to children, as he says in Book Two: “Each [animal] lives with a different appearance (dissimili… specie) and retains the nature of its parents and imitates their ways (mores… imitantur) after its kind” (2.665–6). Later, in Book Three, Lucretius argues that each animal has a psychological profile based on the atomic structure it has inherited from its ancestors. For instance, deer have minds that are by nature “cold” (frigida), which makes them typically skittish, fearful animals. Lions have a mind that is “hot” (calidus), which is why we regularly see each of them “easily boil over in anger” (facile effervescit in ira). The cow (bos), by contrast, is predisposed to “tranquility” (tranquillo), “lives more on peaceful air,” and is “never overmuch excited… never pierced with the cold shafts of fear” (3.288–306). Lucretius’ point is that animals have a lot less control over their genetically inherited impulses than humans do.

It is typical of Lucretius to try to understand humans by examining similar traits in animals. This kind of argument, where one is interested in animals only to understand humans better, has been called by the Italian philosopher Giorgio Agamben the “anthropological machine”. Agamben claims that almost all Western philosophizing about animals has not really been about animals per se but about animals as resources for comparison with humans, usually to the disparagement of animals.

Lucretius points to the random chance (casus) of the universe, while surrounded by animals,some more real than others (M. Burghers, 1682, frontispiece to Thomas Creech’s Oxford edition of that year, the first English translation of Lucretius to be published in full).

Lucretius, however, is often interested in animals for their own sake, not just as a point of comparison. But even when he focuses on animals to learn something more about humans, Lucretius’ point is usually not that humans are superior to animals but that they share many traits with other animals – and that, in fact, we are animals. Lucretius thinks that the human mind, like that of other animals, is best understood in terms of its genetic history. He denies that there is anything like a soul in the sense of something that transcends the physicality of the brain, its evolutionary history, or that is superior in kind (as opposed to capacity) to the brains of other animals.

When Lucretius analyzes how human genetics influence the human mind, he begins by emphasizing that humans are like other animals (3.307–22):

sic hominum genus est. quamvis doctrina politos
constituat pariter quosdam, tamen illa relinquit
naturae cuiusque animi vestigia prima.
nec radicitus evelli mala posse putandumst,
quin proclivius hic iras decurrat ad acris,
ille metu citius paulo temptetur, at ille
tertius accipiat quaedam clementius aequo.
inque aliis rebus multis differre necessest
naturas hominum varias moresque sequacis;
quorum ego nunc nequeo caecas exponere causas,
nec reperire figurarum tot nomina quot sunt
principiis, unde haec oritur variantia rerum.
illud in his rebus video firmare potesse,
usque adeo naturarum vestigia linqui
parvola quae nequeat ratio depellere nobis,
ut nil impediat dignam dis degere vitam.

This is how the human race is [i.e. like other animals]. While education may make some equally polished, it still leaves untouched the original traces of the nature of each person’s mind. We must not think that vices can be ripped out by the roots. One person will still rush too eagerly into bitter anger, another will be attacked too quickly by fear, a third will put up with certain things too calmly. In many other respects the various natures of people must differ, as well as the mores that arise from those natures. I cannot now set forth the hidden causes of these things, nor invent names for all the configurations of the atoms, from which all variety arises. But I see that I can affirm this: so minuscule are the traces of different natures that remain in us beyond reason’s power to expel that nothing keeps us from living a life worthy of the gods.

Here, Lucretius examines whether human genes determine human behavior as they do for other animals. He begins by noting that, however educated one may be, that education “still leaves untouched the original traces (vestigia prima) of the nature of each person’s mind.” So, while education may bring most people up to an equal level of polish (politospariter), there is a natural inequality to the human mind that derives from one’s genetic inheritance.

The forest fire, Piero di Cosimo, 1505 (Ashmolean Museum, Oxford, UK): scholars have argued that the Florentine painter was inspired by Lucretius’ poem.

Lucretius’ real interest in this passage is morality. He makes this clear when he says, “We must not think that “evils” or “vices” (mala) can be ripped out by the roots (radicitus).” It is important to dwell on this statement. Humans, Lucretius thinks, are born with varying genetic tendencies towards vice and wrongdoing. He describes our minds as if they were gardens, full of weeds, the roots of which can never be completely eradicated through education, training, or even, as Lucretius implies here, Epicurean philosophy – the Latin word he uses for all of these things is doctrina.

The self, Lucretius seems to say, will always have to cultivate its inner Epicurean garden, weeding out its genetic predispositions to vice and wickedness. Like the lions, deer, and cows mentioned above, Lucretius thinks that some humans will “still rush too eagerly into bitter anger”, as lions do. Another person “will be attacked too quickly by fear”, like the deer. A third “will put up with certain things too calmly”, like the lethargic cow.

Reconstruction of the garden of the House of the Vettii in Pompeii (in the Boboli Garens, Florence, Italy)

Exactly how the genetics of individual humans differ and exactly how human mores “arise” (oritur) from our genes, Lucretius says he cannot yet tell us. He is willing to bet, however, that “the configurations of the atoms, from which all variety arises” will have a central role to play in explaining the “hidden causes” (caecas causas) of human morality. Lucretius can already see a future for science in which the evolutionary history of the brain will be critical to understanding humanity’s ability to be good and to keep vice in check.

And yet, however great a role genetics play in human and animal behavior, Lucretius thinks that human genes do not determine human morality. He is not a believer in anything like the popular notions of the ‘selfish gene’ or the ‘god gene’, or that our evolutionary background in primate behavior or any other hierarchical tendencies determine us to act in a certain way.

At the same time, Lucretius says above that the “original traces” (vestigia prima) of the evolutionary history of our minds, our mental roots, can never be completely deracinated. So, while genes play a role in how we think and behave, our genetic history is no excuse for vice or immorality. As he says above, the original traces of the mind that “reason (ratio) cannot expel” are “so minuscule” (usque adeo… parvola), that there remains little of our genetic history that must, of necessity, determine whether we behave morally or not.

Lucretius, having slain the dragon of superstition and somehow lost his clothes in the fray, relaxes on a celebratory pedestal while the laurels of poetry are pressed upon him (Louis du Guernier, 1743, the frontispiece to the edition published that year in London by Daniel Browne).

Lucretius’ belief in human moral freedom leads him to his grand conclusion, that “nothing keeps us from living a life worthy of the gods”. This does not mean that we can become gods, only that humans – through education, philosophy, and reason – can pluck enough weeds from our inner garden to make our lives pleasurable in a way that even a god would recognize. It is human reason, Lucretius thinks, a development out of human evolutionary interactions with nature, that allows human morality not to be determined by nature.

Lucretius’ message is that, even if you were not born a winner in the genetic lottery, there are no excuses. Any human can develop their reason through education and philosophy to achieve an inner peace worthy of the life of the gods.

Richard Hutchins is a Visiting Lecturer in the Classics Department of Amherst College. He received his PhD in Classics and Classical Philosophy from Princeton University in 2019. His research focuses on ecological thought in Latin Literature and in Archaic Greek thought. His book project, Lucretius Against Human Exceptionalism, explores nature’s resistance to empire in Lucretius’ De rerum natura. He has published articles about nature and animals in Epicureanism, Stoicism, and Presocratic philosophy. He is currently working on a second book about the animal and pastoral epigrams of Anyte of Tegea.


1 Independently, of course, other non-Western cultures, such as ancient India, also produced theories of atomism.
2 The text of Lucretius’ poem can be explored in Latin via Perseus here; for an English translation, the best option availably freely online is Cyril Bailey’s, hosted here by Liberty Fund.