Evolution and the premortal spirit of man, part 1: All men existed in the spirit before any man existed in the flesh.

Science probably can't say whether all men existed in the spirit before any man existed in the flesh. Even some Church members may not agree that all men existed in the spirit before any man existed in the flesh. But no matter what science says or what certain individuals believe, it is an official teaching of The Church of Jesus Christ of Latter-day Saints that all men existed in the spirit before any man existed in the flesh:

Bible Dictionary:  "Spirit. The word spirit is used in several ways in the scriptures. Probably the basic use has to do with the conscious intelligent individual entity that had an existence previous to mortality. That is, all forms of living things—man, beast, and vegetation—existed as individual spirits, before any form of life existed upon the earth."

Guide to the Scriptures:  "Spirit. That part of a living being which exists before mortal birth, which dwells in the physical body during mortality, and which exists after death as a separate being until the resurrection. All living things—mankind, animals, and plants—were spirits before any form of life existed upon the earth."

1909 First Presidency statement:  "Man, as a spirit, was begotten and born of heavenly parents and reared to maturity in the eternal mansions of the Father, prior to coming upon the earth in a temporal body to undergo an experience in mortality.... All men existed in the spirit before any man existed in the flesh." (Ensign, Feb. 2002.)

The Church's Seminary and Institute manuals teach that all men existed in the spirit before any man existed in the flesh:

Pearl of Great Price Student Manual, Religion 327:  “We were all created untold ages before we were placed on this earth. We discover from Abraham 3:22–28, that it was before the earth was formed that the plan of salvation was presented to the spirits, or ‘intelligences.’ This being true, then man, animals and plants were not created in the spirit at the time of the creation of the earth, but long before.” (© 2000, p.9.)

Seminary D&C Student Study Guide: "Man, as a spirit, was begotten and born of heavenly parents, and reared to maturity in the eternal mansions of the Father, prior to coming upon the earth in a temporal body to undergo an experience in mortality.... All men existed in the spirit before any man existed in the flesh." (Quoting the 1909 First Presidency statement.)"

It is an official teaching of The Church of Jesus Christ of Latter-day Saints that all men existed in the spirit before any man existed in the flesh.