"Evolutionism" is a notion invented by people who don't understand "evolution" and fear that it will undermine the teaching of scripture. It is a bogyman.
Evolution is a discipline that uses scientific methods to discover facts.
Original Sin (or Ancestral Sin) is not a fact that can proven or disproven by application of scientific methods. It is not possible to set up an experiment to see if the experimental Adam and Eve will again disobey and then repeat the experiment over and over to verify that they always do.
The study of evolution is a science. God, and all that He has done, does, and will do, are not subject to scientific investigation.
No scientific research can undermine the teaching of Scripture. (Though it might undermine people's opinions about what those teachings are.)
On the other hand, there are those who call themselves Christians who actually think, because of what evolutionary investigation has discovered, that we must understand the Bible to be a book of mythology because "science has proven theology wrong."
Both views are false. Science cannot prove theology to be wrong and theology cannot prove science to be wrong. IMHO
iakov the fool