According to the October 2016 edition of New Era, "nothing has been revealed about evolution" and "the Church has no official position on evolution."
But the Prophet Joseph Fielding Smith and the Prophet Ezra Taft Benson spoke plainly against evolution. The Prophet Joseph Fielding Smith taught:
"It has been truthfully said that organic evolution is Satan’s chief weapon in this dispensation in his attempt to destroy the divine mission of Jesus Christ. It is a contemptible plot against faith in God and to destroy the effective belief in the divine atonement of our Redeemer� There is not and cannot be, any compromise between the Gospel of Jesus Christ and the theories of evolution. Were evolution true, there could be no remission of sin. In fact there could be no sin. (Ibid., p. 184)"
And the Prophet Ezra Taft Benson taught:
"Now, we have not been using the Book of Mormon as we should. Our homes are not as strong unless we are using it to bring our children to Christ. Our families may be corrupted by worldly trends and teachings unless we know how to use the book to expose and combat the falsehoods in socialism, organic evolution, rationalism, humanism, etc."
If the teachings of our own prophets don't constitute an "official position" for a given topic, then the church doesn't have an official position on anything.