Insights & Perspectives

Linguistic evidence supports date forHomeric epics

Eric Lewin Altschuler1), Andreea S. Calude2), Andrew Meade2) and Mark Pagel2)3)�

The Homeric epics are among the great-est masterpieces of literature. TheIliad’s story of the Trojan Wars tells usthat the epics were almost certainlyproduced sometime after the 12th cen-tury BCE – if indeed the wars were everfought – but the question is how muchlater? Herodotus thought considerablylater: Writing in the Histories Book

II.53 around 450 BCE, he stated thatHomer ‘lived, as I believe, not more than400 years ago’. The most commonlyaccepted date among modern classi-cists, drawing on historical, literaryand archaeological analyses, is aroundthe mid-8th century BCE [1, 2], althoughsome authors propose a more recent7th century BCE date [3].

Here, we investigate whether formalstatistical modelling of languages canhelp to inform this historical question.In particular, we investigate whetherevolutionary-linguistic statistical methodscan be usefully applied to differences inHomeric, Modern Greek and ancientHittite vocabulary items to provide adate for these great works.

Cognate words and rates oflexical change

Languages, like biological species, com-monly evolve by a process of ‘descentwith modification’ [4]. The most obviousway that languages change is to changetheir words or vocabulary. For instance,the English dog is a new word that haslargely replaced the Old English hund tospecify that meaning: the modern Englishhound is now reserved for particularbreeds (e.g. Irish Wolfhound, ScottishDeerhound), dogs used for hunting,and idiomatic references to dog(s), forexample ‘her faithful hound’, ratherthan to dogs in general.

In the study of such lexical change,the basic unit of analysis is the cognate.Cognates are words that derive from acommon ancestral word, just as inbiology homologous genes derive froma common ancestral gene. For example,cognates meaning ‘water’ exist in English(water), German (wasser), Swedish(vatten) and Gothic (wato), reflectingdescent from proto-Germanic (�wator).

The Old English hund is cognate tohound, but the newer word dogrepresents an instance of what is knownas lexical replacement. In previous work

DOI 10.1002/bies.201200165

1) Departments of Physical Medicine andRehabilitation, and Microbiology andMolecular Medicine, University of Medicineand Dentistry of New Jersey, UniversityHospital, Newark, NJ, USA

2) School of Biological Sciences, Lyle Building,University of Reading, Reading, UK

3) Santa Fe Institute, Santa Fe, NM, USA

*Corresponding author:Mark PagelE-mail: m.pagel@reading.ac.uk

Keywords:.dating; evolution; Homeric epics; Iliad; linguistics; phylogeny; statistics

The Homeric epics are among the greatest masterpieces of literature,

but when they were produced is not known with certainty. Here we apply

evolutionary-linguistic phylogenetic statistical methods to differences in

Homeric, Modern Greek and ancient Hittite vocabulary items to estimate a

date of approximately 710–760 BCE for these great works. Our analysis

compared a common set of vocabulary items among the three pairs of

languages, recording for each item whether the words in the two languages

were cognate – derived from a shared ancestral word – or not. We then used

a likelihood-based Markov chain Monte Carlo procedure to estimate the

most probable times in years separating these languages given the percent-

age of words they shared, combined with knowledge of the rates at which

different words change. Our date for the epics is in close agreement with

historians’ and classicists’ beliefs derived from historical and archaeological

sources.

Bioessays 00: 000–000,� 2013 WILEY Periodicals, Inc. www.bioessays-journal.com 1

Ideas

&S

pecu

latio

ns

[5], we have produced statistical esti-mates of rates of lexical replacementfor a range of vocabulary items in theIndo-European languages. A word’s rateof lexical replacement measures theinstantaneous rate at which a word suchas hund gets replaced over time by anew unrelated or non-cognate wordsuch as dog.

We derived our estimates of lexicalreplacement from a formal statisticalmodel applied to a widely studied setof common vocabulary items knownas the Swadesh 200-word list [6]. Therates were evaluated by studying howthe words for each meaning in theSwadesh list evolved along the branchesof a phylogenetic tree of 87 Indo-Europeanlanguages [5].

We found that words reliably differin their rates of lexical replacement.Most words have a 50% chance of beingreplaced by a new non-cognate wordevery 2,000–3,000 years (a word’s lin-

guistic half-life [5]), but among thewords in the Swadesh list there is atleast a 100-fold variation in rate ofchange, such that some have linguistichalf-lives under a millennium whereasothers are expected to last over ten thou-sand years.

The variation in rates of lexicalreplacements makes these vocabularyitems promising candidates for estimat-ing the time of divergence between pairsof languages: rapidly evolving wordsmight be expected to change even amongrelatively closely related languages,whereas more slowly evolving wordsmight remain cognate even among dis-tantly related languages – if all or none ofthe words changed, establishing a datewould be impossible. More generally,given a set of rates and a set of vocabularyitems that have either remained cognateor not between pairs of languages, wecan ask what divergence times bestsatisfy the observed distribution of cog-nacy relations among those languages.

We apply that logic here to estimatethe age of the Homeric epics, usingcomparisons among three sets ofvocabulary items – Hittite, and Homericand Modern Greek. Hittite is an extinctlanguage in the Anatolian branch ofIndo-European. Preserved cuneiformscripts dating to the 13th to 16th centu-ries BCE provide a source of its vocabu-lary. The Anatolian branch of Indo-

European is an outgroup to the mainIndo-European languages containingHomeric and the later Modern Greek(Fig. 1A), and so Hittite is expected tobe widely divergent from the other two.Together, then, comparisons amongHittite, and Homeric and ModernGreek ‘bracket’ Homeric Greek, provid-ing overlapping evidence to where intime Homer’s works fall between them(branch denoted ‘t1’ in Fig. 1A).

We compiled data on cognacyrelationships for the items in theSwadesh 200-word list [7–11], separ-ately for the three language pairs. Weassociated with each word its rate oflexical replacement (the rate at whicha word is replaced by a new unrelatedor non-cognate word) in the Indo-European languages (taken from [5]).

We then estimated the time separ-ating pairs of vocabulary sets by seekingthe times in years that simultaneouslymaximized the likelihood of observingthese distributions of cognacy judge-ments, on the phylogeny in Fig. 1A,given their rates of lexical replacement.Given n ¼ 173 words, the likelihood (L)that any two languages i and j are sep-arated by t units of time given the cog-nacy data D is:

Lðtij jDÞ ¼Ym

k¼1

Pk0 �Yn

k¼mþ1

Pk1;

Figure 1. A: Evolutionary (phylogenetic)relationships among Hittite, Homeric Greekand Modern Greek with approximate agesshown (note: lines not to scale). Indo-European refers to the root or origin of thisfamily of languages. B: frequency histogramof estimated ages for Homer (t1) showingposterior mean estimated age for theHomeric epics (white bar). Age for Indo-European from [12].

E. L. Altschuler et al. Insights & Perspectives.....

2 Bioessays 00: 000–000,� 2013 WILEY Periodicals, Inc.

Ideas

&S

pecu

lati

on

s

where Pk0 ¼ ð1� e�rktÞ, Pk1 ¼ ðe�rktÞ, mcorresponds to words in the Swadeshlist that we scored as not cognatebetween any two language families,n–m counts the words scored as cog-nate, and rk is the rate of change forthe kth word as estimated in the Indo-European languages. The overall likeli-hood is the product of the three pairwisecomparisons.

An inferred date for theHomeric epics

We were able to extract informationabout shared cognates among the threelanguage-pairs for 173 of the 200Swadesh items. Consistent with expec-tations, Hittite and Modern Greek sharethe fewest cognates (13.3%), followed byHittite and Homeric Greek at 19.1% oftheir vocabulary, and the figure forHomeric and Modern Greek is 50%(Table 1). In each case, the wordsremaining cognate between a pair haveslower rates of lexical replacement thanthose that have changed (Table 1, allp-values <0.0001). The mean differencein rates of replacement is greatest forthe youngest pair (Modern-Homer)where change is restricted largely torapidly evolving words, and least forthe oldest pair (Hittite-Modern) whereeven many slowly evolving wordshave been replaced owing to the greaterlength of time they have been separated.

We derived a posterior distributionof dates for Homer from a BayesianMarkov chain Monte Carlo method(Fig. 1B) that proposed times for t1 whilesimultaneously integrating over two

prior distributions of dates, one forthe Indo-European root and the otherfor Hittite. The posterior distributionreturns a posterior mean estimate ofthe date for Homer’s works of 707BCE, with 95% confidence intervals(sometimes denoted credible intervals)ranging from 61 BCE to 1351 BCE.The upper confidence interval doesnot rule out a far earlier date for theepics than is commonly believed, butsuggests (Fig. 1B) that it is unlikely theywere produced near to the time of theTrojan Wars. The lower (younger) limitof approximately 61 BCE might seemabsurd given historical evidence andbeliefs, but is not wholly implausibleon linguistic grounds alone, even if –as Fig. 1B shows – it is improbable.

Conclusions

Our analysis gives a formal quantitativeestimate of a date for the Homericepics that agrees with the commonlyaccepted 8th century BCE origin ofthese great works. Our posterior distri-bution of dates is also consistent withHerodotus’ remark that would place theepics around 850 BCE, but would treatas unlikely any suggestion that Homermight have been a ‘war correspondent’recording the events of the Trojan Waras they happened, if indeed they everdid (of course, the epics were originallyan oral tradition so we cannot know ifour dates reflect when they were pro-duced or when they were eventuallywritten down).

Our analysis is not informed orconstrained in any way by historical,cultural or archaeological information

about Homer or his works, being derivedsolely from information on sharedcognates among Hittite, and Homericand Modern Greek, and rates oflexical replacement in Indo-Europeanlanguages. In spite of this, our estimateddate falls roughly in the middle of theclassicists’ and historians’ preferreddate for Homer, representing a predic-tion spanning nearly three millennia.This, along with the consistency ofthe results (Table 1), demonstrates aremarkable regularity in the ways thatwords are replaced over time, and illus-trates that language can be used, likegenes, to aid in the investigation ofquestions in history, archaeology andanthropology [13].

Our Bayesian approach is easilyextended to include other sources ofinformation, such as might be obtainedfrom historical accounts. For instance,given that Herodotus was aware ofHomer, we might have restricted oursearch (Fig. 1B) to times earlier than450 BCE. As an illustration, we haverepeated our Bayesian analysis using anormally distributed prior for the ageof Homer centred on 800 BCE with astandard deviation of 200 years. Thismakes a 450 BCE or even younger dateunlikely but not impossible.

The new model returns a date forHomer of 762 BCE with 95% confidenceintervals from 376 to 1157 BCE. It is intri-guing in this light that the ‘Nestor’s cup’[14], a vase excavated from an AncientGreek site in Italy, contains an inscrip-tion that some scholars think refers to aline from the Iliad, and is dated to�740–720 BCE. Equally, the new 95%upper limit falls in the middle of the 12thcentury, the period during which somescholars think the Trojan wars mighthave been fought.

Along with the historical and otheraccounts of Homer’s great works, ouranalysis of common vocabulary itemsin the Iliad increases our confidencein its age, and shows how even fictionaltexts can preserve traces of history.

AcknowledgmentsWe thank Theo van den Hout for help inidentifying cognate words betweenHittite and Homeric Greek, and Hittiteand Modern Greek. MP thanks theEuropean Research Council for its gen-erous support of this research.

Table 1. Comparisons among Hittite, and Homeric and Modern Greek

Data Hittite-HomerHittite-ModernGreek

Homer-ModernGreek

Cognate/not cognatea 33/140 23/150 87/86

Percent cognate 19.1 13.3 50.3

Replacement rate forcognateb

1.62 � 1.26 (sd) 1.28 � 1.03 1.19 � 1.63

Replacement rate fornon-Cognate

3.32 � 1.77 3.26 � 1.76 3.54 � 1.83

a Refers to number of words out of 173 (see text) judged cognate between the twolanguages;

b Rates of lexical replacement taken from [5].

..... Insights & Perspectives E. L. Altschuler et al.

Bioessays 00: 000–000,� 2013 WILEY Periodicals, Inc. 3

Ideas

&S

pecu

latio

ns

References

1. Fox RL. 2009. Travelling Heroes: Greeks andtheir myths in the epic age of Homer. NewYork: Random House. p 360–4.

2. Janko R. 1982. Homer, Hesiod and theHymns: Diachronic Development in Epic Diction.Cambridge: Cambridge University Press.

3. West ML. 1966. Hesiod: Theogony. Oxford:Clarendon Press.

4. Pagel M. 2009. Human language as a culturallytransmitted replicator. Nat Rev Genet 10: 405–15.

5. Pagel M, Atkinson QD, Meade A. 2007.Frequency of word use predicts rates of

lexical evolution throughout Indo-Europeanhistory. Nature 449: 717–20.

6. Swadesh M. 1952. Lexico-statistic dating ofprehistoric ethnic contacts. P Am Philos Soc96: 453–63.

7. Gehring A. 1891. Index Homericus. Lipsiae inAedibus B.G. Teubneri.

8. Owen WB, Goodspeed EJ. 1969. HomericVocabularies: Greek and English Word List forthe Study of Homer. Norman: University ofOklahoma Press.

9. Cunliffe RJ. 1963. A Lexicon of the HomericDialect. Norman: University of OklahomaPress.

10. Chantraine P. 1968. Dictionnaire Etymologiquede la Langue Grecque: Etymological Dictionaryof the Greek Language. Paris: Klincksieck.

11. Kloekhorst A. 2007. Etymological Dictionaryof the Hittite Inherited Lexicon. Leiden: Brill.

12. Gray RD, Atkinson QD. 2003. Language-tree divergence times support the Anatoliantheory of Indo-European origin. Nature 426:435–9.

13. Barbrook AC, Howe CJ, Blake N, RobinsonP. 1998. The phylogeny of The CanterburyTales. Nature 394: 839.

14. http://en.wikipedia.org/wiki/Nestor’s_Cup(January 2013.).

E. L. Altschuler et al. Insights & Perspectives.....

4 Bioessays 00: 000–000,� 2013 WILEY Periodicals, Inc.

Ideas

&S

pecu

lati

on

s