Mormons do genealogical research to find their ancestors for the purpose of baptizing for the dead. The Bible says this is useless. (Let the Scriptures Speak, p. 65, Suzanne Bishop)
But avoid foolish disputes, genealogies, contentions, and strivings about the law; for they are unprofitable and useless.
1 Timothy 1:4
nor give heed to fables and endless genealogies, which cause disputes rather than godly edification which is in faith.
Early genealogies were to prove that Jesus is the Messiah. The records of all genealogies were kept in the temple. After God recorded the lineage of Jesus (Luke 3 and Matthew 1), the temple was destroyed by Titus in 70 AD. Not only can you not trace your genealogy prior to this time, but God is letting us know by this that it is now complete. There is no further genealogical work to be done! (Let the Scriptures Speak, p. 65, Suzanne Bishop)
My unanswered question was:
Since the Bible obviously instructs us to avoid genealogies, why do LDS justify the time and energy spent, which is a fair amount, on genealogical research?
I was initially devastated when I received this answer that doing temple work for our dead ancestors is not something God intended us to do, yet overjoyed to find the truth that the Bible tells us our genealogy work is complete and to not waste our time on genealogies. We need to learn to have faith. Genealogies cause disputes and are unprofitable and useless! I did not, and still do not, gain faith by disputing unprofitable or useless topics. I have faith that my ancestors are already enjoying heaven with God. There is no need for me to baptize them by proxy. They are in such a better place where they are now. God is completely sovereign and can do SO much more than I can. I do not believe HE needs my earthly help with this.