I’ve read that DNA can be used to estimate how many generations there have been since our most recent common ancestor, presumably Adam. These studies indicate he lived at least 100,000 years ago, and yet, D&C 77 says (and you said in another question) that the Earth is less than 7,000 years old. How do you reconcile these differences in dates?
I am not as knowledgeable about DNA as I am some of the other aspects of science. But I do have a good general understanding of how science works. Its building blocks are facts that they can be tested and get repeatable results. From those fact they infer outward to other things. Things that aren’t so easily testable. When they go beyond something they can test in a lab, they start need to make some assumptions. One of the biggest assumptions usually made is that various ‘things’ remain constant. If these it don’t remain constant then reasoning and logic are shown as flawed.
Therefore when science is said to have ‘proved’ something, it is more accurate to say its science’s best answer barring new data or understanding.
Now lets move on to the question of time. I did not say, and Doctrine and Covenants does not say that the earth is less then 7,000 years old.
Lets start with Abraham 5:13
But of the tree of knowledge of good and evil, thou shalt not eat of it; for in the time that thou eatest thereof, thou shalt surely die. Now I, Abraham, saw that it was after the Lord’s time, which was after the time of Kolob; for as yet the Gods had not appointed unto Adam his reckoning
Please note that time before Adam and the Fall was not reckoned by Adam’s or earthly or temporal time. It was measured by the Lord’s time and we don’t know how long that is.
Then we get Doctrine and Covenants 77:6
Q What are we to understand by the book which John saw, which was sealed on the back with seven seals?
A. We are to understand that it contains the revealed will, mysteries, and the works of God; the hidden things of his economy concerning this earth during the seven thousand years of its continuance, or its temporal existence.
Between these two scriptures we can see that we have a creative period of the earth’s existence which is unknown length (Although many have opinions on this). Then after creation, and after Adam gets appointed his reckoning, we have 7000 years when the work that the earth was created for is to be done.