In LDS Truth Claims video #34 Brett McDonald appears to mis-characterize Runnell’s argument, which Brett attempts to outline at the beginning of the lecture:

The LDS Church requires members to believe that there was “no death” of any kind on the earth prior to 7,000 years ago and that Adam and Eve are the first “humans”

Jeremy does not actually argue this point (i.e., that a member is “required” to believe those things). To be sure, I scanned the CES letter to confirm, and nowhere in the CES letter does he say a member “must” or is “required to” believe those things.

Now, elsewhere in the document Runnells says things like “I’m supposed to believe… X, Y, or Z”. But the “supposed to” is clearly meant to convey the idea that he is expected to believe those things, because Church leaders have taught it regularly and it’s been taught or is being taught in our official Church manuals, not that he “must” believe those things.

And, the underlying assumption—which McDonald does not address—is that if leaders are teaching as absolutely true ideas which are not, in fact, true, then this is a good reason to question the reliability of other things the leader is saying. The logic is simple: if many of the testable truth-claims a leader has made turn out to be false, why would we trust them to be any more accurate with the un-testable? Said another way, why should we place our confidence in these men who literally believe (and have an expectation that we also believe) in the truth of stories that the scientific data strongly suggest are not veridical?

The point Jeremy does advance in the letter, that members are expected to believe these things, seems justified given the data. Here’s how FairMormon discussed the flood:

Without a doubt, the flood is always treated as a global event as it is taught by Church leaders. This is not likely to ever change, since it is based directly upon a straightforward reading of the scriptures.

Leaders have mostly backed away from “no death for any living organism before the fall.” However, they still teach a literal Adam and Eve. Jeffery R. Holland, in April 2015, stated:

In our increasingly secular society, it is as uncommon as it is unfashionable to speak of Adam and Eve or the Garden of Eden or of a “fortunate fall” into mortality. Nevertheless, the simple truth is that we cannot fully comprehend the Atonement and Resurrection of Christ and we will not adequately appreciate the unique purpose of His birth or His death—in other words, there is no way to truly celebrate Christmas or Easter—without understanding that there was an actual Adam and Eve who fell from an actual Eden, with all the consequences that fall carried with it.

But I’m unaware of any way in which a literal Adam and Eve, an Adam and Eve who 1) tilled the earth, 2) had domesticated animals, and 3) were the literal parents to all humans on earth today) may be reconciled with the human migration data. See the section “Adam and Eve” in Questions to Ask and consider how Heath Ogden, an evolutionary biologist and LDS Bishop, attempts to reconcile the data and note that his reconciliation fails to account for all 3 of the points above.

In addition, any reconciliation needs to acknowledge that LDS leaders taught these principles in general conference. For instance, Bruce R. McConkie taught, in October 1984:

I propose some simple tests that all of us may take to determine if we are true to the faith. They consist of a few basic questions, all of which must be answered correctly in order to gain the full blessings of the gospel in this life and inherit eternal life in the realms ahead.

…

From among many questions that all of us must one day answer, let me test you on these:

Test two: Do I believe in the fall of Adam?

There is no salvation in a system of religion that rejects the doctrine of the Fall or that assumes man is the end product of evolution and so was not subject to a fall.

True believers know that this earth and man and all forms of life were created in an Edenic, or paradisiacal, state in which there was no mortality, no procreation, no death.

In that primeval day Adam and Eve were “in a state of innocence, having no joy, for they knew no misery; doing no good, for they knew no sin.” (2 Ne. 2:23.)

But in the providences of the Lord, “Adam fell that men might be; and men are, that they might have joy.” (2 Ne. 2:25.)

By his fall, Adam introduced temporal and spiritual death into the world and caused this earth life to become a probationary estate.

These teachings in official channels allow us to invoke another of Jeremy’s questions from the CES letter: ~”why should we trust Brett McDonald’s interpretation of what is important or required when someone with priesthood keys has already said it explicitly? Who gave Brett McDonald the right to dismiss McConkie’s 1984 General Conference talk and Holland’s 2015 talk? Aren’t we supposed to ‘live by every word which proceedeth forth out of the mouth of God’?”