Who was Joseph’s father, Jacob or Heli?

Both Matthew and Luke give Jesus geneaology, tracing back his lineage through the generations. It is not long, however, before the genealogies diverge. In fact, taking Jesus as the first generation, the genealogies disagree by the third.

In Matthew, the genealogy begins with Abraham and ends with Jesus. As it closes, we are told that the father of Jesus was Joseph, and the father of Joseph was Jacob:

… and Jacob the father of Joseph the husband of Mary, of whom Jesus was born, who is called the Messiah. [Matthew 1:16 (NRSV)]

In Luke, the genealogy is ordered in reverse, beginning with Jesus and running through Abraham all the way to Adam and thence to God. As it opens, we are told that the father of Jesus was Joseph, and the father of Joseph was Heli:

Jesus was about thirty years old when he began his work. He was the son (as was thought) of Joseph son of Heli… [Luke 3:23 (NRSV)]

So who was Joseph’s father, Jacob or Heli?