To my knowledge, the last statement to truly address evolution by the PCUSA was in 1969 from the PCUS. The conclusion from the study is presented below. You can also find it at the PCUSA website under Evolution Statement.
EVOLUTION AND THE BIBLE
Primary Reference: GA Minutes 1969: 59-62
Conclusion from the Study
Neither Scripture, our Confession of Faith, nor our Catechisms, teach the Creation of man by the direct and immediate acts of God so as to exclude the possibility of evolution as a scientific theory. Scripture states that "out of the ground" the Lord God formed every beast, Genesis 2:19, and "of the dust of the ground" the Lord God formed man, Genesis 2:7. Genesis 1 teaches that according to the Word of God there came into being Light, Firmament (called Heaven), the Earth and the Seas. Then, God said: "Let the waters bring forth" and "Let the earth bring forth." After the creation of Light, the Firmament and the Earth, after the Earth and the Waters brought forth plant, aquatic and animal life, then God said: "Let us make man." This man, Adam, meaning both a man and man, is by nature both individual and corporate. The name Adam is simply a generic term for man brought forth from the Earth. Genesis 1 describes Creation as taking place in six days; however, it is not necessary to understand the Genesis account as a scientific description of Creation. Our Confession of Faith says:
"It pleased God the Father, Son and Holy Ghost, for the manifestation of the glory of his eternal power, wisdom and goodness, in the beginning, to create or make of nothing the world, and all things therein, whether visible or invisible, in the space of six days, and all very good.
After God had made all other creatures, he created man, male and female, with reasonable and immortal souls . . ." (Chapter IV).
The Larger Catechism answers the question "How did God create man?" as follows: "After God had made all other creatures, he created man, male and female; formed the body of man of the dust of the ground, and the woman of the rib of man; endued them with living, reasonable, and immortal souls; made them after his own image . . ."(Q. 17)
It may be that the Westminster Divines understood the "six days" as well as such phrases as "of the dust of the ground" and "the rib of man" in a literal sense; but, as they were merely using the words of Scripture with no intention to argue the theory of evolution (of which they had never heard), we are free to interpret their words in a different sense, just as we now do the words of Scripture. Nowhere is the process by which God made, created or formed man set out in scientific terms. A description of this process in its physical aspects is a matter of natural science. The Bible is not a book of science. As John Calvin said, commenting on Genesis: "To my mind, this is a certain principle, that nothing is here treated of but the visible form of the world. He who would learn astronomy and other recondite arts, let him go elsewhere." (Genesis Commentary — on Chap. 1, verse 6).
If the Confession of Faith, or the Catechisms, appear in some manner to support the position of the General Assemblies of 1886, 1888, 1889 and 1924 this is not because of Scripture itself but rather because Scripture was interpreted with 17th Century perspectives and presuppositions.
Some form of evolutionary theory is accepted by the majority of modern scientists. The Darwin Centennial celebration, composed of fifty outstanding experts on the various phases of evolutionary theory, expressed the meaning of evolution as follows: "Evolution is definable in general terms as a one-way irreversible process in time, which during its course generates novelty, diversity, and higher levels of organization. It operates in all sectors of the phenomenal universe, but has been most fully described and analyzed in the biological sector." (Evolution After Darwin, edited by Sol Tax, University of Chicago Press, containing the University of Chicago Centennial papers and discussion, 1959)
Our responsibility as Christians is to deal seriously with the theories and findings of all scientific endeavors, evolution included, and to enter into open dialogue with responsible persons involved in scientific tasks about the achievement, failures and limits of their activities and of ours. The truth or falsity of the theory of evolution is not the question at issue and certainly not a question which lies within the competence of the Permanent Theological Committee. The real and only issue is whether there exists clear incompatibility between evolution and the Biblical doctrine of Creation. Unless it is clearly necessary to uphold a basic Biblical doctrine, the Church is not called upon and should carefully refrain from either affirming or denying the theory of evolution. We conclude that the true relation between the evolutionary theory and the Bible is that of non-contradiction and that the position stated by the General Assemblies of 1886, 1888, 1889 and 1924 was in error and no longer represents the mind of our Church.
We re-affirm our belief in the uniqueness of man as a creature whom God has made in His own image.