Sunday, 2 May 2021

Prometheus and liver regeneration

Prometheus suffers a gruesome punishment in Greek myth. By day an eagle tears at his liver; by night the liver fully regenerates. Repeat.

Since the 1990s it’s been fashionable to take the story as describing a real medical phenomenon, the liver’s unique ability to regenerate. But how did the Greeks know about liver regeneration?

Easy: they didn’t. Liver regeneration wasn’t discovered until the 1800s. It’s just another case of people repeating something because other people have repeated it, without any evidence.

The torture of two Titans, close in several respects to Theogony 517–525. Left: Atlas holding up the sky, tormented by a snake. Right: Prometheus bound with a stake driven through his bonds, and Zeus’ eagle devouring his liver. (Laconian kylix, Cerveteri, ca. 560–550 BCE; Mus. Vaticani 16592. Source: Van Gulik et al. 2018)

Here’s the earliest version, in a poem composed around 700 BCE:

(Zeus) bound prismatic-thinking Prometheus in fetters,
painful bonds, and he drove a stake through in the middle.
And he set a long-winged eagle on him. It devoured his liver,
which was immortal, and it grew back on all sides, as much
at night as the long-winged bird would eat throughout the day.
Hesiod, Theogony 521–525

The Giant Tityos has a similar punishment in the afterlife:

And I saw Tityos, Earth’s famous son,
lying on the ground, covering a full nine plethra [ca. 280 metres];
and two vultures sitting one on either side tore at his liver,
reaching into his innards. His hands couldn’t keep them away ...
Homer, Odyssey 11.576–579

(Translations mine.) There are explanations for the role of the liver in the Prometheus myth. The most robust ones in print are: (a) The liver was important because of extispicy, the practice of divination by examining an animal’s entrails. (b) The ancient Greeks thought of the liver as the seat of emotions that weren’t based on rationality, especially desire, anger, and pain.

These explanations tell us why the liver was important, but they don’t tell us what its importance has to do with Prometheus. Here I’m adding a still more proximate explanation. It wasn’t about pain, or Prometheus representing the inner psyche, or anything like that: it’s about vengeance.

For Greeks of the Archaic period (ca. 800–480 BCE), mutilating an enemy’s body was an especially potent form of revenge. Mutilating the liver was especially potent, but that’s just a matter of degree. The mutilation is where the meaning lies. The fact that it’s done to his liver makes the revenge more potent, and the fact that it’s done every day makes it more potent still. For ancient Greeks, this was the purest form of vengeance there could be.

Tityos tormented by vultures, as depicted by a fictional statue in Assassin’s Creed: Odyssey (2018). Here the vulture is tearing at Tityos’ intestine, not his liver. (Source: AC Wiki)

Literature review

No classicist has ever adequately addressed in print the claim that Prometheus’ liver alludes to real-life liver regeneration. The only exception is a short piece in Dutch for a generalist audience, where a classicist was the third author (out of three; Van Gulik et al. 2018).

The pathology literature, by contrast, has both discussed the claim and debunked it. Unfortunately the debunking isn’t as widely read as one might like: I didn’t have access to the database that it’s in, so I’m very grateful to Carl Power and John Rasko for their help in sending me a copy of their article. Go team pathology!

The most important pieces on this subject are, on the classicist side, Collins (2008) on ancient liver divination and its connection to the Prometheus story; and on the pathologist side, Power and Rasko (2008), with a full survey of the evidence and comprehensive debunking of the myth.

The classicists

Martin West’s commentary on the Theogony (1966: 312–315) gives a summary of earlier scholarship on Prometheus’ punishment. He doesn’t touch on a potential link to real-life liver generation: no one suggested that link until 1994 (see below). West focuses on (a) the story of Heracles rescuing Prometheus; (b) the relationship between Prometheus’ and Tityos’ punishments; and (c) possible origins for the myth of a Titan/Giant being punished eternally.

The most relevant of these for us is the relationship between Prometheus and Tityos. Bapp (1896: 45) argued that Tityos was the primary version of the story; West rejects this. They’re both off target. Bapp’s argument was that Tityos’ offence was lust, and he suffers in his liver because the Greeks thought of the liver as the seat of emotions. But that has nothing to do with Prometheus. West claims that the liver wasn’t the seat of the emotions until the time of Aeschylus; and that’s actually false — see Archilochus fr. 234 ed. West (yes, the same West) = fr. 131 ed. Edmonds, ‘You do not retain anger in your liver’.

Cassanmagnago (2009: 937), the only Theogony commentary since West’s, agrees with Bapp’s view and cites an ancient gloss on Hesiod (schol. Th. 523):

The liver, that is, the motivator of reason. For they say that the mental faculties are in the liver.

The Greeks usually thought of the liver as the seat of the passions, not reason: we’ll return to this below in the discussion.

No Odyssey commentary touches on the nature of Tityos’ punishment at all. Vergil’s Aeneid mentions Tityos’ punishment, but Horsfall’s note (2013: 414–415) just repeats West’s views on Prometheus. Roscher’s encyclopaedia of myth adds little (1886–1937.iii: 3041–3043 on Prometheus, v: 1035–1039 on Tityos), except for mentioning a Christian rationalist interpretation which reinterpreted Tityos’ suffering in the afterlife as pain caused by arrows in his liver.

Derek Collins (2008) is the best available discussion of the practice of examining animals’ entrails, or extispicy, as a form of divining the future. The practice of examining an animal’s liver, in particular, is called hepatoscopy. Physical models of the liver, made of terracotta or bronze, and sometimes with annotations for diviners to refer to, have been found in Mesopotamia and in Etruscan Italy. None have been found in Greece. But Greek textual sources and pictorial art give plenty of evidence of Greek extispicy and the central importance of the liver. As well as Collins (2008), see also Van Straten (1995: 156–157); Flower (2008: 32–34, 44–50, 188–189).

In 2018 Hugo Koning became the first classicist, and the first Hesiod scholar, to discuss liver regeneration in connection with Prometheus: see Van Gulik et al. (2018). The other two authors are pathologists. The article isn’t new research, and it stays on the fence about whether the Greeks knew about liver regeneration. The only thing it adds that wasn’t already covered by Power and Rasko (2008) is that the Greeks believed blood was particularly associated with the liver; and even this is put more clearly by Collins (2008: 324–325, with bibliography). The two pathologist authors, without Koning, later contributed to a book on Prometheus and his liver (Van Rosmalen et al. 2020; chap. 14 is on liver regeneration), which unfortunately I haven’t seen.

An extispicy scene on a Greek vase. The scene is formulaic. The divination is in a military context, as is usual with such scenes. A soldier, centre, holds up an animal’s liver to inspect it, while an enslaved boy stands by with the rest of the entrails. On the iconography of extispicy scenes on Greek vases, see Durand and Lissarrague (1979); Van Straten (1995: 156–157). (Belly amphora attributed to the Kleophrades Painter, Vulci, ca. 500 BCE; Würzburg, Martin von Wagner Museum L 507. Source: Van Straten 1995, Fig. 165)

The pathologists

Real-life liver regeneration was first described in the 19th century by Emil Ponfick (1889, 1890, 1891), and confirmed by experiments on rats in the 1930s and 1950s (see Van Gulik et al. 2018, in the section ‘Regeneratie van een rattenlever’, with further bibliography).

The idea that the Prometheus story alludes to liver regeneration was first suggested by Chen and Chen (1994). Their earlier book on the history of the liver (1984) doesn’t contain the idea, though it does mention Prometheus in passing. Their evidence in the 1994 piece, such as it is, is (a) the superficial resemblance between Prometheus’ regrowing liver and the regeneration discovered by modern experimentation; (b) a passing mention of liver divination.

That isn’t any kind of evidence. Power and Rasko (2008) debunk the claim fully. Power and Rasko address extispicy, noting that it’s doubtful that that could provide the occasion for discovering liver regeneration; and they investigate ancient Greek medical texts that discuss the liver, but they find not the slightest trace of evidence of any awareness of the phenomenon. In particular they emphasise that early medical descriptions of the liver appear to have been based on animal livers, with one to five lobes, until the time of Herophilus around 300 BCE. Herophilus gives the first accurate description of a human liver (fr. 60 ed. von Staden; see von Staden 1989: 162–163, 227–228) — and even he was totally unaware of liver regeneration.

In spite of that, many papers continue to echo Chen and Chen’s brief account. Several take for granted the supposed link between Prometheus and real liver regeneration (Michalopoulos and DeFrances 1997: 60; Koniaris et al. 2003: 634; Michalopoulos 2007: 286). Others question the claim, but are non-committal (Tiniakos et al. 2010; Riva et al. 2011: 1132; Van Gulik et al. 2018; the latter two cite Power and Rasko). Only a few refer to liver divination (Michalopoulos 2007: 286; Power and Rasko 2008: 421–422). None make the effort to engage with ancient medical texts, other than Power and Rasko (2008: 422–423).

Tiniakos et al. (2010) try to shift the emphasis to Tityos. But they spend most of their time on modern-era artistic treatments of the story. An interesting corner of art history, perhaps, but not any kind of evidence about ancient medicine. Several papers discuss hepatocentrism, the ancient idea that the liver was the seat of the passions (Power and Rasko 2008: 424–425; Riva et al. 2011: 1133; Orlandi et al. 2018; Van Gulik et al. 2018, in the section ‘Zetel van het leven’).

From all of this it can be seen that Power and Rasko’s piece (2008) is by far the most thorough survey of all aspects of the evidence. It is also the most accurate.

Prometheus bound depicted by two Flemish painters, Peter Paul Rubens (ca. 1612; Phildelphia Mus. of Art) and Jacob Jordaens (ca. 1640; Wallraf-Richartz-Museum, Köln)

Folk etymologies

Tiniakos et al. (2010: 358) assert that certain etymologies are responsible for aspects of the Prometheus and Tityos stories. They claim that the Greek word ἦπαρ hē̂par ‘liver’ is also found in the form ήδαρ ḗdar, and this shows that it’s derived from ἡδονή hēdonḗ ‘pleasure’, and this is the reason why the liver is attacked. They also claim that Τιτυός Tituós ‘Tityos’ is derived from τίσις tísis ‘retribution’, and this explains Tityos’ punishment.

The claims are entirely wrong. ḗdar is an invention. The etymologies aren’t based on any patterns or accepted linguistic principles. Even so, some subsequent pieces have unfortunately repeated the claims (Orlandi et al. 2018: 987).

In reality hē̂par ‘liver’ comes from the Proto-Indo-European root *iekʷ-r ‘liver’ (compare Sanskrit yákṛ-t ‘liver’, Latin iecur ‘liver’). The transformation of early Greek medial /kʷ/ into Classical Greek /p/ is a common one: compare Mycenaean i-qo ‘horse’ > Classical ἵππος híppos, Mycenaean e-qe-(ta) ‘follow’ > Classical ἕπ(ομαι) hép(omai). Meanwhile hēdonḗ ‘pleasure’ comes from Greek ἡδ(υ)- hēd(u)- ‘sweet, enjoy’, Proto-Indo-European *sueh₂d-ú- ‘sweet’. For more reliable information about etymologies, see Beekes (2010).

As for Tityos’ name Tituós, both it and the pastoral name Τίτυρος Títuros (which Tiniakos et al. also cite) are based on a reduplicated form titu-, from the verbal stem *tu- ‘be strong, be solid, swell’ (< Proto-Indo-European *teuH-). If Tityos’ name had come from ti- ‘compensate, pay’, he would have been called something like Tísmos or Tístēs. Roscher (1886–1937.v: 1033–1034) gives a detailed discussion of the name’s real etymology. The root *tu- also appears in Greek in the word τυρός turós ‘cheese’, and possibly in τύλη túlē ‘bulge, callus’ and τύφη túpʰē ‘a plant used for padding’. In other words, ‘Tityos’ means ‘the strong one’; ‘Tityros’ is a wordplay, with connotations of ‘strength’ and a pastoral link with cheese.


Chen and Chen (1994: 755) cited a key passage for interpeting the Prometheus story, though they didn’t appreciate its significance. In the Iliad, Hecabe cries out for vengeance against Achilles, who has killed her son Hector (Homer, Iliad 24.212–214):

I wish I could take the middle of his liver,
keep hold, and eat it: then I’d have revenge
for my son!

No academic commentary on the Iliad thinks to draw a link to Prometheus or Tityos. But they do note that this is an echo of other similar sentiments in the Iliad. Achilles, wanting revenge on Hector, would ‘cut off [his] flesh and eat it’ (Il. 22.346–347); Zeus reminds Hera, ‘you’d eat Priam and his sons raw’ (Il. 4.34–36). Later literature has parallels too: Xenophon, Hellenica 3.3.6 (‘they would gladly eat them raw’), and Anabasis 4.8.14 (‘if we can, we should eat them raw’); Menander, Dyskolos 468 (‘Bite you? I’d eat you alive!’).

This is part and parcel of an ongoing theme in the Iliad which Charles Segal calls ‘the theme of the mutilation of the corpse’ (Segal 1971). Corpse mutilation becomes more extravagantly violent and gruesome as the epic progresses. On page 1 we’re told that corpses will become ‘feasts for dogs and birds’ (Iliad 1.4–5); by book 20, Achilles’ rage fills an entire river with corpses and blood for the fish to eat, to the point where the river god himself rises up against him. Book 22 sees Achilles violate Hector’s body, and book 24 finally resolves the macabre theme, with Hector’s body being miraculously protected from decomposition and given a proper burial.

Hecabe’s desire to eat Achilles’ liver is the moment when this theme hits peak body-horror.

Prometheus the bringer of fire looks benevolently over ice skaters at the Rockefeller Center, New York (Paul Manship, 1934)

This is the key for interpreting the stories of Prometheus’ and Tityos’ punishments. The story is a revenge fantasy; the liver just represents the degree of that revenge. The reason why this is so is comfortably explained by the various points raised by Collins, Power, and Rasko. Power and Rasko (2008: 422):

There are many explanations of why the Greek mythmakers targeted Prometheus’ liver for terrible and repeated abuse. The best explanations do not depend on the idea that the Greeks actually knew about the liver’s regenerative capacity.

1. The liver as the seat of passions. The liver was consistently seen as commanding desires, passions, and the mental faculty, as Collins describes very fully (2008: 327–335):

  • Archilochus, fr. 234 West: anger resides ‘on the liver’
  • Aeschylus, Agamemnon 792: pain approaches ‘onto the liver’
  • Sophocles, Aias 938: anguish can pierce or approach ‘towards the liver’
  • Euripides, Suppliants 599: fear sits ‘beneath the liver’
  • Democritus, 66 C 23.7 ed. Diels and Kranz: the liver is ‘responsible for desire’
  • Plato, Timaeus 70a–e: the appetitive part of the soul is between the midriff and the navel, bound like a wild animal in the form of the liver

2. The liver as the organ of blood. See Collins (2008: 324–325). We know that the Greeks sometimes speculated that blood was produced by the liver. Some extant sources actually reject this idea (Aristotle, On the parts of animals 666a.24–36), but others endorse it (Empedocles 31 B 150 ed. Diels and Kranz ‘the liver rich with blood’; P. Mich. inv. 1 col. iv ‘the conversion into blood of food ... is performed by the liver’). Van Gulik et al. (2018) point out that a bleeding liver is likely to have been seen by early Greeks as a fatal wound.

3. The liver in divination. See Collins (2008). The anonymous 5th century BCE tragic play Prometheus bound actually links Prometheus directly to hepatoscopy, when Prometheus declares that he has benefited humanity by teaching them the art of divination (488–495):

(Prometheus:) The flight of crooked-taloned birds I outlined
clearly: which ones are auspicious by nature,
and which are bad omens; ...
and the smoothness of their entrails, and the colour
their bile must have to be pleasing to the divinities,
and the colourful beauty of the lobe; ...

‘Smoothness of entrails’ refers specifically to the liver. The belief was that emotions like anger and fear could ruin the liver’s smoothness, making it useless for divination (Collins 2008: 332–334; in Philostratus’ mostly-fictional Life of Apollonius of Tyana 8.7.10–15, Apollonius is charged with using human livers for divination, and this is part of his defence). The ‘lobe’ (lobós) in the last line could refer to various parts of the liver, or even to the liver as a whole (von Staden 1989: 228); the number of lobes varied depending on which animal the liver had come from, and this was more than a century before Herophilus conducted his first human dissection.

All of these are legitimate reasons why the liver is the target of choice in the punishments of Prometheus and Tityos. But they aren’t the reason why their body parts are being attacked. The story of Prometheus’ torture isn’t about hepatoscopy, philosophy, or medicine: it’s about vengeance.


Thanks again to Carl Power and John Rasko for their help in preparing this account.


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