4 And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,...
Jesus Christ, God manifest in the flesh (1 Timothy 3:16) , knows and confirms the Genesis account in this one verse -- God created Adam and Eve fully formed. And stepping out of eternity he communicated this to man. He is the Creator (John 1:1,2).
So, any Christian who doesn't know this is grossly misinformed. But most likely is a Christian in name only and is not saved, since it is the Holy Spirit which teaches all truth and every saved person has the "earnest" of his inheritance. (Ephesians 1,2).
While I agree scripture supports creationism. Some of our fellow Christians may not have read or studied in detail the Genesis account. I was a believer 5 years before I studied Genesis inductively and became a young earth creationist.