When 1 Timothy cautions against "endless geneologies", is it talking about the Bible? It seems that at the time that 1 Timothy was written, "certain people" had become much too interested in genealogies:


  1 Timothy 1:3-4
  3 I repeat the request I made of you when I was on my way to Macedonia, that you stay in Ephesus to instruct certain people not to teach false doctrines
  4 or to concern themselves with myths and endless genealogies, which promote speculations rather than the plan of God that is to be received by faith.
  5 The aim of this instruction is love from a pure heart, a good conscience, and a sincere faith.
  6 Some people have deviated from these and turned to meaningless talk,
  7 wanting to be teachers of the law, but without understanding either what they are saying or what they assert with such assurance.


Other passages in the Bible, such as Genesis 10,
Genesis 5, and Matthew 1, list various geneologies. These hardly seem to qualify as "endless", unless one has a very short attention span. So what exactly is 1 Timothy talking about? I would guess, especially based on the context, that "certain people" were more or less fabricating geneologies about biblical figures, but on what basis? And is this a prohibition against being interested in any genealogies, or is it referring to a specific sort of interest? Most importantly, is it a prohibition against reading and being interested in the geneological parts of the Bible itself, provided that one remains interested in only what is said therin?
The focus of this invective isn't so much on the genealogies themselves as it is the way in which people use them to puff them themselves up.  Even barring earthly lineages, the poor of the church of Corinth managed to put themselves into faction. In 1 Corinthians 3, Paul writes:

Brothers and sisters, I could not address you as people who live by the Spirit but as people who are still worldly—mere infants in Christ. 2I gave you milk, not solid food, for you were not yet ready for it. Indeed, you are still not ready.  3You are still worldly. For since there is jealousy and quarreling among you, are you not worldly? Are you not acting like mere humans? 4For when one says, “I follow Paul,” and another, “I follow Apollos,” are you not mere human beings?
5What, after all, is Apollos? And what is Paul? Only servants, through whom you came to believe—as the Lord has assigned to each his task.

Notice Paul's focus here - he is concerned that his church isn't &quot;growing up.&quot; When the focus is on where one comes from, the focus necessarily is moved off of what one has become.
Note also in the text you quote, that the problem with 'myths and genealogies' is that they lead simply to 'endless speculation.' Put another way, Paul is admonishing believers to stick to the actual teaching, rather than indulging in the desire to read as much into a text as is desired.  The genealogies in Scripture are there for a reason - they place Scripture in a particular time and place, and show that God is no respecter of persons. (Abraham, in Genesis 11, is just another guy in another line).  When people dwell on these things, however, they are looking for themselves - puffing themselves up - and that is not the point.