When 1 Timothy cautions against "endless geneologies", is it talking about the Bible?

A reference to the Bible?

When 1 Timothy cautions against "endless genealogies", is it talking about the Bible?

I propose that the answer to this question is no. Let's establish this 2 ways:

1. The subsequent Pastoral letter to Timothy holds the scriptures in high esteem:

15 And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus.

16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness (2 Tim. 3:15-16)

That's high praise. Paul held the Tanakh to be authoritative and sacred (see also 1 Cor. 15:3-4, Romans 15:4)

2. The Bible--as a collection of 66 or 73 books--didn't exist yet.

What genealogies are referred to?

What then is Paul referring to? I'll suggest 4 possibilities for consideration; they are not mutually exclusive.

1. Aeons - as noted in other responses, there were early Christians who developed very imaginative mythical beings and gave them extensive pedigrees and backstories. Such ideas were scathingly denounced by (for example) Irenaues of Lyons as a perversion of the scriptures (see here).

2. Fictitious accounts of Old Testament characters - Jewish hagiographies -- "embellished accounts of biblical worthies" were common (see here). It is unsurprising that an avid student of the Tanakh would counsel against making up stories to "enliven" or "improve upon" sacred texts.

3. Claims of superiority based on ancestry - One of the principal difficulties Paul addressed in his letters was the challenge of bringing together Jews & Gentiles in the Christian faith. Paul was quite clear that salvation was available to all, not just the physical descendants of Abraham (see Romans 1:16). That some descendants of Abraham considered themselves superior to those who could not trace their ancestry to Abraham--or descended through what were considered "illegitimate" lines (e.g. the Samaritans)--is evident from passages such as Matt. 3:9; John 4:9; John 8:39,52-53. Paul's teachings come down decidedly against trying to prove one's superiority based on one's genealogy.

4. Distraction by Speculation - I'll offer a brief personal anecdote. I once asked a professional genealogist how it was possible to trace one's genealogy back to Adam (I had heard of people doing this). Apparently the process is to trace your genealogy back to Charlemagne, who in his day had his scholars trace his genealogy back to the Bible, and from there follow the Biblical genealogies back to Adam. The genealogist cited this passage from 1 Timothy and advised that this would be a waste of time, especially considering the potentially spurious genealogies crafted by Charlemagne's scholars. This would fit right in with the myths & speculations mentioned in this passage, as things that can overly distract people's attention from things that matter more.

--

Conclusion

Paul is not condemning genealogy in general or the Biblical genealogies specifically, but the speculative, prideful, or even heretical uses to which genealogies/myths/story-telling could be put.

Genealogies may refer to one of two ideas. One is a physical bloodline. Another is a spiritual bloodline. Both are mentioned in the Bible.

Physical genealogies were in fact used to prove certain histories, relationships, and descendants. These were used to arrive at what was considered certified truth. Here are examples. They led from Adam to Jesus. They led from the first high priest Aaron to the last high priest. They led from David to Jesus. These written genealogies were necessary to positively prove position, birthright, and identity.

Spiritual genealogies are similar, showing spiritual authority from one Christian to the next. For example, Jesus instructed the apostles to preach the gospel and breathed on them the Holy Spirit. Paul lays hands on Timothy and instructs him to carry on the work. Simon the Socerer on the other hand attempts to be part of this lineage, but Peter rejects his offer of money. This “laying on of hands” is a foundational teaching (Heb 6:2).

So, we find “useful” genealogies, but to what was Paul speaking regarding the “useless” genealogies in these two verses?

Neither give heed to fables and endless genealogies, which minister questions, rather than godly edifying which is in faith: so do. 1 Tim 1:4

But avoid foolish questions, and genealogies, and contentions, and strivings about the law; for they are unprofitable and vain. 1 Titus 3:9

In context in both instances, Paul contrasts the teaching of faith with the teaching of the law. In other words, certain people were using their genealogies to prove their teaching authority, but their teaching skewed from the truth of the gospel.

PHYSICAL BLOODLINE

As mentioned, there was a time and place for proving certain physical bloodlines through historically agreed upon records. These things were written down and relied upon. When someone could not prove their history, they were rejected from certain positions (Neh 7:64).

Could genealogies be misused? Absolutely, this is to what Paul is referring.

This will be controversial to some, but this scriptural example makes the most sense within the context that Mary and Joseph indeed had children as scripture and early tradition tell us. Certainly, a claim to being the physical brother from the same mother to the Son of God would carry some weight and influence. Alternatively, this claim could also arise within the context of being a step-brother from an earlier marriage of Joseph’s. This relationship helps explain why James, as opposed to Peter or Andrew or any of the other apostles who actually believed and walked with Jesus prior to His ascension, was chosen as first bishop of Jerusalem.

Imagine the argument. Those may have walked with Jesus, but James is of His bloodline. He too has descended from David. He is an heir of the kingdom. He should be first bishop in our center of the earth.

In scripture, we find these things shown as clashes between certain parties.

For before that certain came from James, he [Peter] did eat with the Gentiles: but when they were come, he withdrew and separated himself, fearing them which were of the circumcision. Gal 2:12

And the day following Paul went in with us unto James; and all the elders were present. Acts 21:18

This incident led to an uproar. Paul was arrested. But recall that the decision regarding the Mosaic Law had already been settled, yet there it was again.

And after they had held their peace, James answered, saying, Men and brethren, hearken unto me: Acts 15:13

For many, James was the go between of heaven and earth, trying to sooth both sides of the dispute as diplomatically as possible. For Paul, there is only one gospel. This physical bloodline led to strife, promoting speculations about God’s plan received by faith, rather than works. This continues today.

SPIRITUAL BLOODLINE

The next incident was also about the truth of the gospel; that is, we are saved by grace through faith not of our works, but of God’s. Who is the truth? Who has the truth? How do we know?

Now this I say, that every one of you saith, I am of Paul; and I of Apollos; and I of Cephas; and I of Christ. Is Christ divided? was Paul crucified for you? or were ye baptized in the name of Paul? 1 Cor 1:12-13

People were elevating certain disciples, rather than elevating the truth of the gospel. It is not who says what, but what is said by whom. The plumbline of truth is not men, but what God has said. How do we know for certain? Scripture, the “this is written”.

CONCLUSION

OP: I would guess, especially based on the context, that "certain people" were more or less fabricating geneologies about biblical figures, but on what basis?

This is true as we saw. People and their followers invent genealogies about themselves, about their histories. The basis is a claim to physical or spiritual bloodlines.

So, while some in Paul’s time were and still today are busy establishing blood or spiritual genealogies in order to prove their position, their power, their prestige, or their teachings, Paul was dismissing the spiritual and physical bloodlines as carrying any weight and admonishing instead their focus on the truth of Christ crucified and risen.

When 1 Timothy cautions against "endless geneologies", is it talking about the Bible?

3 As I desired thee to remain at Ephesus when I went into Macedonia, that thou mightest charge some not to teach otherwise,

4 Not to give heed to fables and endless genealogies: which furnish questions rather than the edification of God, which is in faith. - 1 Timothy 1:3-4

These endless genealogies may be talking about different aspects of the term as was understood in the days of the Apostle Paul in his days. Interpretation is not all together clear here.

The word genealogy occurs only twice in the New Testament: 1 Timothy 1:4, and Titus 3:9. In these passages commentators explain the word as referring to the Gentile theogonies, or to the Essene generation of angels, or to the emanation of spirits and aeons as conceived by the Gnostics, or to the genealogies of Jesus Christ, or finally to the genealogies of the Old Testament construed into a source of an occult doctrine. Some even appeal to Philo in order to refer St. Paul's expression to the various stories and fables told about Moses and the Patriarchs. - Genealogy (in the Bible)

The First Epistle to Timothy consists mainly of counsels to his younger colleague and delegate Timothy regarding his ministry in Ephesus. Ephesus at the time of St. Paul was a Greek city of Greek pagan beliefs. Ephesus was also one of the seven churches of Asia cited in the Book of Revelation; the Gospel of John may have been written there.

The First Epistle of Paul to Timothy, usually referred to simply as First Timothy and often written 1 Timothy, is one of three letters in the New Testament of the Bible often grouped together as the pastoral epistles, along with Second Timothy and Titus. The letter, traditionally attributed to the Apostle Paul, consists mainly of counsels to his younger colleague and delegate Timothy regarding his ministry in Ephesus (1:3). These counsels include instructions on the organization of the Church and the responsibilities resting on certain groups of leaders therein as well as exhortations to faithfulness in maintaining the truth amid surrounding errors.

Thus, it would not surprise me that he was talking about the theogony of the Greeks which are complete fables and myths.

The Theogony i.e. "the genealogy or birth of the gods"1) is a poem by Hesiod (8th – 7th century BC) describing the origins and genealogies of the Greek gods, composed c. 730–700 BC. It is written in the Epic dialect of Ancient Greek and contains 1022 lines.

Hesiod's Theogony is a large-scale synthesis of a vast variety of local Greek traditions concerning the gods, organized as a narrative that tells how they came to be and how they established permanent control over the cosmos. It is the first known Greek mythical cosmogony. The initial state of the universe is chaos, a dark indefinite void considered a divine primordial condition from which everything else appeared. Theogonies are a part of Greek mythology which embodies the desire to articulate reality as a whole; this universalizing impulse was fundamental for the first later projects of speculative theorizing.

Further, in the "Kings and Singers" passage (80–103) Hesiod appropriates to himself the authority usually reserved to sacred kingship. The poet declares that it is he, where we might have expected some king instead, upon whom the Muses have bestowed the two gifts of a scepter and an authoritative voice (Hesiod, Theogony 30–3), which are the visible signs of kingship. It is not that this gesture is meant to make Hesiod a king. Rather, the point is that the authority of kingship now belongs to the poetic voice, the voice that is declaiming the Theogony.

Although it is often used as a sourcebook for Greek mythology,5 the Theogony is both more and less than that. In formal terms it is a hymn invoking Zeus and the Muses: parallel passages between it and the much shorter Homeric Hymn to the Muses make it clear that the Theogony developed out of a tradition of hymnic preludes with which an ancient Greek rhapsode would begin his performance at poetic competitions. It is necessary to see the Theogony not as the definitive source of Greek mythology, but rather as a snapshot of a dynamic tradition that happened to crystallize when Hesiod formulated the myths he knew—and to remember that the traditions have continued evolving since that time.

Hesiod was probably influenced by some Near-Eastern traditions, such as the Babylonian Dynasty of Dunnum,7 which were mixed with local traditions, but they are more likely to be lingering traces from the Mycenaean tradition than the result of oriental contacts in Hesiod's own time.

The decipherment of Hittite mythical texts, notably the Kingship in Heaven text first presented in 1946, with its castration mytheme, offers in the figure of Kumarbi an Anatolian parallel to Hesiod's Uranus–Cronus conflict. - Theogony

It is possibly a reference to the gnostic emanations (genealogies of angels) but in this case it seems to do more with Jewish folklore. Timothy does not really seem to attack gnosticism as is done in an Epistle like Colossians. It certainly has nothing to do with he genealogical records of Christ, which were so very important and which were clear enough that no record of disputes is recorded. Most likely These arguments were not about Christ, or angels, but about the law:

But avoid foolish controversies and genealogies and arguments and quarrels about the law, because these are unprofitable and useless. (Titus 3:9, NIV)

The arguments about genealogies seem to be about the law and mixed up with myths, so that the genealogical records were part of the myth and endless stories that had nothing to do with Christ or the gospel:

The expression “myths and genealogies” is one. It must not be divided, as if Paul were thinking, on the one hand, of myths, and on the other, of genealogies. The apostle refers undoubtedly to man-made supplements to the law of God (see verse 7), mere myths or fables (2 Tim. 4:4), old wives’ tales (1 Tim. 4:7) that were definitely Jewish in character (Titus 1:14). Measured by the standard of truth, what these errorists taught deserved the name myths. As to material contents these myths concern genealogical narratives that were largely fictitious.

If you have ever read Jewish Haggadah, it is the most creative kind of biblical exegesis that makes even the weirdest modern day false teachings seem quite tame. From the smallest little idea found somewhere in the Bible they could erect long descriptive claims that had nothing to do with the text or even the Bible. It is fascinating if it were not actually destructive:

We feel at once that here we have been introduced into the realm of typically Jewish lore. It is a known fact that from early times the rabbis would “spin their yarns”—and endless yarns they were!—on the basis of what they considered some “hint” supplied by the Old Testament. They would take a name from a list of pedigrees (for example, From Genesis, I Chronicles, Ezra, Nehemiah), and expand it into a nice story. Such interminable embroideries on the inspired record were part of the regular bill of fare in the synagogue, and were subsequently deposited in written form in that portion of The Talmud which is known as Haggadah. (NEW TESTAMENT COMMENTARY Exposition of The Pastoral Epistles, William Hendriksen and Simon J. Kistemaker)