Question: If Genesis chapter 1 speaks of Adam in a plural sense i.e. the bulk of humanity, and Genesis chapter 2 speaks of Adam (singular) in the garden why is Adam the individual relegated to chapter 2 seeing it is from him that Christ descended?
Answer: The assumption that Genesis chapter 1 speaks of Adam in a plural sense and chapter 2 in a singular sense is correct. The book of Genesis appears to stick to a plan, we could call it a literary device: The chosen people through whom Christ’s line descends are mentioned second, and the “bulk of humanity” get the first mention. After all, there needs to be a bulk of people from whom to choose the chosen people.
We see that Cain’s family and descendants are explained to us first and then Seth’s story (through whom Christ descended) is mentioned second.
In a similar way in Genesis 10 Japheth and Ham’s family lines comes before Shem (through whom Christ descended).
In Genesis 25 Ishmael’s toledoth is mentioned before Isaac’s (through whom Christ descended).
Also in the same chapter we note that Esau arrives before Jacob (through whom Christ descended).
We see that Genesis seems to consider the non-chosen before the chosen, that is probably why the majority of humankind are mentioned in Genesis chapter 1 and Adam the man chosen to begin the descent of Christ is mentioned second in Genesis chapter 2.