Tuesday, November 21, 2017

Another test case for phylogenetics and textual criticism: the Bible

This is a two-part blog post. Here, I will introduce a particular stemmatological problem, along with the studies of it to date; and in a subsequent post I will discuss possible phylogenetic analyses that might be applied.


This year marks the celebration of 500 years since Martin Luther famously proposed his 95 religious theses, thus presaging the Protestant Reformation of the Western Christian Church. In line with this, it is worth discussing a subfield of textual criticism and stemmatics deeply influenced by the Reformation: Biblical criticism. While the importance of written texts to Christianity begins at least in the 2nd century, the theological doctrine of the sola fide (“by scripture alone”, regarding the infallible and final authority in all matters), along with translation work and individual study of the Bible, paved the way, sometimes unwillingly, to scientific approaches of Biblical criticism equivalent to those of secular literature.

The seminal figure in textual criticism of the New Testament was Hermann Reimarus (1694-1768), apparently the first to apply the methodology of literary texts to religious ones. As in the case of literary criticism, it is hardly a coincidence that Biblical criticism developed in the same cultural framework that would support and promote the idea of biological evolution and the tools for establishing genealogical trees and networks. This is especially so when considering the secularization of that society, in which proving the human origin and transmission of sacred texts was deemed an important act of civic freedom. Along with this was the parallel radicalization of some religious positions, such as denouncement as heresy of scientific studies of religious texts (nowadays objected to by most Christian doctrines that stated the imperative of serious research of the sacred texts).

A concrete problem: the synoptic gospels

The most important problem in the textual criticism of the New Testament is the “synoptic gospels" one, involving the three Gospels of Mark, Matthew, and Luke. These gospels have strikingly similar narratives that relate many of the same stories, with similar or identical wording. Like the other canonical gospel, John, these texts were composed around the last quarter of the first century by literate Greek-speaking Christians, only becoming canonical at least a century after their composition.

The synoptic gospels differ from similar sources, such as the non-canonical Gospel of Thomas, in being biographies with a clear religious motivation, and not just a collection of sayings. When compared to the Gospel of John, the three synoptic gospels are distinct in apparently being written by and for a Jewish community that was not on the verge of breaking from the Jewish synagogue, also favoring short and simple sentences.

However, the most important proof of their genealogical relationship is the text itself. The table below shows the reconstructed Greek original of each gospel for the episode of Jesus’ recruitment of a tax collector (an episode missing from the non-synoptic Gospel of John). The text in blue is the material shared by any two of the gospels, and the text in red is common to all three of them. [This is adapted from Smith (2017); on Wikipedia there is a further example, referring to the episode of the cleansing of a leper, see https://en.wikipedia.org/wiki/Synoptic_Gospels#Example.]

Matthew 9,9

Mark 2,13-14

Luke 5, 27-28
Καὶ παράγων ὁ Ἰησοῦς ἐκεῖθεν εἶδεν ἄνθρωπον καθήμενον ἐπὶ τὸ τελώνιον, Μαθθαῖον λεγόμενον, καὶ λέγει αὐτῷ· Ἀκολούθει μοι. καὶ ἀναστὰς ἠκολούθησεν αὐτῷ. Καὶ ἐξῆλθεν πάλιν παρὰ τὴν θάλασσαν· καὶ πᾶς ὁ ὄχλος ἤρχετο πρὸς αὐτόν, καὶ ἐδίδασκεν αὐτούς. καὶ παράγων εἶδεν Λευὶν τὸν τοῦ Ἁλφαίου καθήμενον ἐπὶ τὸ τελώνιον, καὶ λέγει αὐτῷ· Ἀκολούθει μοι. καὶ ἀναστὰς ἠκολούθησεν αὐτῷ. Καὶ μετὰ ταῦτα ἐξῆλθεν καὶ ἐθεάσατο τελώνην ὀνόματι Λευὶν καθήμενον ἐπὶ τὸ τελώνιον, καὶ εἶπεν αὐτῷ· Ἀκολούθει μοι. καὶ καταλιπὼν πάντα ἀναστὰς ἠκολούθει αὐτῷ.

The relationships between the gospels, such as the so-called “triple tradition”, is summed by the graph below, from the Wikipedia article on the synoptic gospels. Mark, the shortest text, has almost no unique material (only 3%, in part superfluous adjectives and Aramaic translations) and is almost entirely (94%) reproduced in Luke. Matthew and Luke have their share of unique material (20% and 35%, respectively), which suggests independence, except for a "double tradition" of common material of about a quarter of the contents of each one, including notable passages such as the “Sermon of the Mount”. The parallelisms of these two gospels are found not only in their contents, but also in their arrangement, with most episodes described in the same order and, in case of displacements, with blocks of episodes moved together while preserving their internal order.

Previous studies

Such similarities were already noted in the first centuries of Christianity. This raises typical genealogical questions regarding topics such as priority (which gospel was written first) and dependence (which gospel was used as a source).

As for the first question, due to textual and theological evidence, a well-established majority of commentators favors the hypothesis of Marcan priority — that is, that the gospel of Mark is the oldest, and both Matthew and Luke used it as a source. As for the second question, a major point of dispute is the double tradition of Matthew and Luke, which can only be properly explained in terms either of descent or of a common ancestor. The two leading hypotheses are the one of a lost gospel (referred as “Q”, after the German Quelle [“source”]), and the one by Austin Farrer, according to whom Matthew used Mark as its source and Luke then used both of them. But these are not the only hypotheses that have been proposed, as shown in the next set of diagrams (also from the Wikipedia article above).

Augustinian Theory
Q Hypothesis
Farrer Theory
Jerusalem School Hypothesis

The first fully developed theory was actually proposed by Augustine of Hippo back in the 5th century, which is essentially the one by Farrer, but with Matthew in place of Mark (i.e., supporting a Matthean priority). Given Augustine’s authority as a “Father of the Church”, his view was not disputed until the late 18th century, when Johann Jakob Griesbach published a synopsis of the three gospels and developed a new hypothesis, swapping Mark and Luke in the dominant explanation. Griesbach’s scientific approach led to the first application to Biblical problems of textual criticism, then in development in the German towns of Jena and Leipzig where he lived.

In 1838, Christian Weisse proposed the “Q” Hypothesis, mentioned above, asserting that Matthew and Luke were produced independently, both using Mark plus a lost source. This source was described as a lost collection of sayings of Jesus, along with feeble indirect evidence of its existence. This hypothesis was further developed by Burnett Streeter in 1924, with the proposal of “proto-versions” of both Mark and Luke — the wording of the canonical versions we have today would then be the product of later revisions, influenced by all of the texts.

During the past fifty years, due to advances in textual criticism and new manuscript analyses, the independence of Luke in relation to Matthew has been questioned, with diminishing support for the Q Hypothesis. A now leading position holds for Farrer’s hypothesis, along with alternative trees such as the one by the Jerusalem School, according to which a lost Greek anthology “A” (postulated as the translation of a collection of saying either in Hebrew or in Aramaic) was directly or indirectly used by all gospels, including John.


Considering the analogies between literary and genetic texts that we have already discussed on this blog, it is clear that this topic should be an interesting anecdote to share around phylogenetic water-coolers. The four texts can be divided into two “families” of gospels, the synoptic (taxa: Matthew, Mark, and Luke) and non-synoptic (taxon: John). Their similarities suggest a distant common ancestor, probably oral traditions, as reported by Christian writers of the first and second centuries such as Papias.

The relationship between the taxa of the first family, however, is far from clear, as their relative dates cannot be determined with confidence. We might be faced with processes that, by analogy with biology, can be explained as gene pool recombinations and horizontal gene transfers – even though the most likely explanation is the one of direct descent, possibly from unknown taxa.

In literary terms, we must also consider features such as Matthew clearly being written by someone highly familiar with aspects of Jewish law, possibly asserting the Jewish component of the preaching while perceiving a universal tendency for the new faith. We must also consider the fact that Mark provides no ancestral lineage for Jesus, while Matthew traces him from a line of kings and Luke from a line of commoners — clearly stating the theological point of view of each gospel. Other aspects are worth consideration, such as the fact that what we today identify as the Gospel of Luke is likely to have been the first part of a once single document that included what is now the book of the “Acts of the Apostles”.

While I must admit that my research has been limited to some googling of keywords, it is curious that a topic that has attracted so much attention for millennia, from serious academic scholarship to conspiracy theories, and from impressionistic reviews to advanced statistical modeling, does not seem to have been covered by phylogenetic analyses so far. Given the range of data and literature, it should actually look like a prime candidate for such application, even from an outsider point of view. This viewpoint is in fact discussed in a review by Christian P. Robert of a book called The Synoptic Problem and Statistics by Andry Abakuks:
The book by Abakuks goes […] through several modelling directions, from logistic regression using variable length Markov chains [to predict agreement between two of the three texts by regressing on earlier agreement] to hidden Markov models [representing, e.g., Matthew’s use of Mark], to various independence tests on contingency tables, sometimes bringing into the model an extra source denoted by Q. Including some R code for hidden Markov models. Once again, from my outsider viewpoint, this fragmented approach to the problem sounds problematic and inconclusive. And rather verbose in extensive discussions of descriptive statistics. Not that I was expecting a sudden Monty Python-like ray of light and booming voice to disclose the truth! Or that I crave for more p-values (some may be found hiding within the book). But I still wonder about the phylogeny… Especially since phylogenies are used in text authentication as pointed out to me by Robin Ryder for Chauncer’s [sic] Canterbury Tales.
We can certainly list among the reasons for such omission the diffidence of the textual community towards phylogenetic methods, especially when performed by people from outside the field; but the potential reception problems for texts of enormous religious significance cannot be ruled out. However, one the reasons might be far more trivial: the fact that, just as in the case of historical linguistics, we don’t have digital structured databases of the trove of data about this topic. Most of the literature is not even properly digital, at best with scanned PDFs. Furthermore, the data are usually far from perfect for such usage, as in the case of the synopsis by Smith (2017), which looks more like a typed table than a true database.


In a future post, I will explore the problems of the synoptic gospels from a phylogenetic point of view, also releasing a minimal dataset. Until then, those interested in the topic can find a lot of discussion on a mailing list devoted to the scholarly study of the synoptic gospels, Synoptic-L.


Abakuks, Andris (2014) The Synoptic Problem and Statistics. London: Chapman and Hall / CRC.

Goodacre, Mark (2001) The Synoptic Problem: a Way Through the Maze. New York: T & T Clark International. (available on Archive.org)

Robert, Christian P (2015) The synoptic problem and statistics [book review]. https://xianblog.wordpress.com/2015/03/20/the-synoptic-problem-and-statistics-book-review/

Orchard, Bernard; Longstaff, Thomas RW (1979) J.J. Griesbach: Synoptic and Text - Critical Studies 1776-1976. Cambridge: Cambridge University Press.

Smith, Mahlon H (2017) A Synoptic Gospels Primer. http://virtualreligion.net/primer/