Here is a brief overview in Sidney Jellicoe's the Septuagint and Modern Study:
As with Aquila, details of the life and person of Theodotion are scanty. While the evidence of Epiphanius might be regarded as suspect, that of Irenaeus cannot be discounted. As Irenaeus was himself an Asiatic, his statement that Theodotion was an Ephesian and a proselyte to Judaism may be founded on personal knowledge. Jerome makes him an Ebionite, but it is more probable that he was a Jew of the Dispersion who for a time became loosely attached to Christianity (hence the origin of the Ebionite tradition) but whose Jewish nurture and training, too strong to be permanently overcome, finally brought him back to his native faith. His identification with Jonathan ben 'Uzziel in modern writers has already been noted.
To Theodotion belongs the distinction of having supplanted the current Greek version of the Book of Daniel, so that of the original LXX version only one Greek manuscript was known until 1931, when the Chester Beatty Papyrus X added a further witness. The reason for this supersession of the LXX, to which we shall return later, was unknown to Jerome, who comments on the matter and adds: 'this one thing I can affirm — that it differs widely from the original, and is rightly rejected.'
Swete in 1902 simply mentioned the existence of the two versions of Daniel as 'a perplexing problem which calls for further consideration', and R. R. Ottley in 1920, after briefly summarizing the situation, merely commented that 'the matter needs further consideration.'
Both versions lay before Origen and both received a place in the Hexapla, the Alexandrian being that of the fifth column. Some important information on their status is to be culled from the Epistle to Africanus. As insufficient attention has been paid to this source it might be profitable here to submit it to further examination. According to Origen's statement in the second paragraph both LXX and Theodotion were in circulation in the Christian Churches, since the two are claimed as 'ours' in contradistinction to the Hebrew and the version of Aquila which 'follows the Hebrew readings.'
For in Daniel itself [writes Origen6], I found the word 'bound' followed in our versions (italics the present writer's) by very many verses which are not found in the Hebrew at all, beginning (according to one of the copies which circulate in the Churches) thus: 'Ananias and Azarias and Misael prayed and sang unto God' down to . . . 'that they were alive'. Or, as in another copy, from 'And they walked, etc.,' down to 'all ye that worship, etc'. . . . Of the copies in my possession whose readings I have given, the one follows the Seventy, and the other Theodotion. . . .
One would naturally, from this context, construe Theodotion as 'the other copy' in circulation in the Christian Church, a judgement that appears to be borne out by what follows:
And just as the History of Susanna which you call a forgery is found in both, together with the passages at the end of Daniel, so they give also these passages, amounting, to make a rough guess, to more than two hundred verses. And in many other of the sacred books I found sometimes more in our copies than in the Hebrew, sometimes less. I shall adduce a few examples, since it is impossible to give them all.
After noting that in the Book of Esther neither the prayer of Mordecai nor that of Esther, and neither the letter to Haman nor that of Mordecai in the name of the King is found in the Hebrew, Origen observes that in Job the words from 'It is written, that he shall rise again with those whom he raises' to the end, are not in the Hebrew and so not in Aquila's edition, but they are found in the Septuagint and in Theodotion's version, and there agree with each other at least in part. Further examples of discrepancies between 'our copies' are cited from Job, the term 'our copies' occurring three times in this particular context, while in what follows he speaks of 'our copies', 'the copies in use in our churches' (para. 4), 'ours' and 'our scriptures' (para. 5).
We must, however, take into consideration the possibility of another interpretation. Origen is here arguing, in response to the challenge of Africanus, for the authenticity of those passages in 'our copies' which constitute an excess over the Hebrew. Clearly he aligns Aquila with the latter, but fails to make specific the position of Theodotion. Does he regard this as a Jewish version akin in this respect to Aquila but at the same time, along with the LXX, witnessing to the authenticity of readings indigenous to the original Hebrew but which, to account for their absence in the text of his day, and in the conforming Greek of Aquila, he accuses the Jews of having expunged? This is a possible interpretation, especially in the light of paragraph which reads as follows:
In all these cases consider whether it would not be well to remember the words, You shall not remove the ancient landmarks which your fathers have set. Nor do I say this because I shun the labour of investigating the Jewish Scriptures, and comparing them with ours, and noticing their various readings. This, if it be not arrogant to say it, I have already to a great extent done to the best of my ability, labouring hard to get at the meaning in all the editions and various readings; while I paid particular attention to the interpretation of the Seventy, lest I might to be found to accredit any forgery to the Churches which are under heaven, and give an occasion to those who seek such a starting-point for gratifying their desire to slander the common brethren, and to bring some accusation against those who shine forth in our community. And I make it my endeavour not to be ignorant of their various readings, lest in my controversies with the Jews I should quote to them what is not found in their copies, and that I may make some use of what is found there, even although it should not be in our Scriptures. For if we are so prepared for them in our discussions, they will not, as is their manner, scornfully laugh at Gentile believers for their ignorance of the true reading as they have them.
In the absence of any clear statement on the part of Origen, we incline to the view that both LXX and Theodotion are to be included in the references to the versions circulating in the Churches, though his assertion that he 'paid particular attention to the interpretation of the Seventy, (para. 5) would appear to accord pride of place to the LXX.
Equally difficult to determine is the date at which the LXX of Daniel gave place to Theodotion. If the interpretation favoured above be correct, Theodotion and the LXX were both in circulation in the Christian Church when Origen wrote his Letter to Africanus. But here again the date of the Letter is uncertain, a matter to which we shall revert in due course. For the moment there is nothing to suggest that at this time Theodotion's Daniel had superseded the LXX. Certainly by the time of Jerome (late fourth century) the transition had taken place, and the appearance of Theodotion as the Daniel text in Codex Vaticanus suggests that it had already established itself by the earlier part of that century. If, again, we take into account the evidence of Chester Beatty X, which gives the LXX text (though caution is necessary in drawing any certain conclusions from a single manuscript), the transition may be placed approximately in the second half of the third century, and if a name were desiderated it would be that of Origen himself. According to Jerome1 Origen, in his lost Stromata, announced his intention of using Theodotion's Daniel in preference to the LXX . — an objective which certainly reached fruition, as, in the words of Gwynn, 'the result of an examination an examination of all the citations of Daniel, some of them long and important passages, that occur in Origen's extant works, is to prove that they all agree almost verbatim with the text of Theodotion now current, and differ, in some instances materially as well as verbally, from that of the reputed LXX as derived from the Chisian manuscript'.
Here the matter of the two versions must stand for the present. From it we turn to the more weighty problem, namely the incidence of Theodotionic readings before, and sometimes long before, Theodotion. The writer of the Epistle to the Hebrews, who almost consistently follows LXX, agrees with Theodotion in his only reference to Daniel (Heb. xi. 33 = Dan. vi. 23). 3 In Revelation, where Daniel is frequently cited, it is on the side of Theodotion that the balance of support lies. Mark xiv. 62, in citing Daniel vii. 13, agrees with Theodotion (μετὰ, 'with the clouds') whereas Matthew xxiv. 30, xxvi. 64 cite, with LXX, as ἐπὶ ('upon'). In a few cases the New Testament Theodotionic citations extend to books other than Daniel (John xix. 37, cf. Rev. i. 7 = Zech. xii. 10; 1 Cor. xv. 54 = Isa. xxv. 8), a feature which gave Schurer cause to observe 'either Theodotion itself is older than the Apostles, or it has given a "Theodotion" before Theodotion'.
Outside the New Testament Clement of Rome (a.d. 96) cites Daniel vii. 10 with the Theodotionic reading ἐλειτούργουν for LXX ἐθεράπεουν (1 Clem. xxxiv. 6), while Justin Martyr, in a longer extract from the same chapter of Daniel (vv. 9-28) gives, in almost equal proportions, characteristic readings from both versions (Dialogue with Trypho xxxi. 2-7). Hermas (Vis. IV. ii. 4) has Theodotion's rendering of Daniel vi. 23; Irenaeus, despite his objections to the supplanters Aquila and Theodotion, cites Daniel according to the latter; and Clement of Alexandria, in his few citations from Daniel, follows Theodotion with an occasional LXX reading (Paed. ii. 8; Strom. i. 4, 21). The Epistle of Baruch, described by Montgomery as 'the most striking parallelism of an early Greek document with [the] Theodotion [version] of Daniel', embodies both agreements and differences, the latter being ascribed by Montgomery to the translator's having drawn on his memory. Both Theodotion and LXX seem to have been current in North Africa and to have influenced the Old Latin. Burkitt concluded that Tertullian represents a form of the LXX differing slightly from Origen's edition, while Cyprian uses a mixed text in which Theodotion sometimes predominates.[Sidney Jellicoe, the Septuagint and Modern Study pp. 85 - 88]
The connection with the Old Latin Bible is of particular interest as it has been argued by Clabeaux and Schmid that the Marcionite gospel bears striking resemblance to the Old Latin text. Could it be coincidence that there exists a Roman-Marcionite parallel with respect to both gospel and Old Testament translations? I don't think so.
