According to the book of Genesis in the Old Testament Adam and Eve had only two sons. How, then, did mankind multiply?

Answer:

There are two opposing views as to the question whether all human beings came from the first human couple (monogenism) or from several (polygenism). Both views arose at about the same time in various locations (East Asia, Africa). The bible does not provide a clear answer. According to modern exegetical knowledge the biblical narrative of the creation of the first human couple does not represent a scientific, historic position on the question of the origin of human beings, but proclaims the faith that God is the creator of mankind and the Lord of human history. In the New Testament the Adam-Christ Parallel (Romans 5:12-21; 1 Corinthians 15:20-22) from a literary point of view is based on the Old Testament creation narrative, but it is really about the contrast between the salvation opened up by Christ and the situation before Christ.