names from 1 Chronicles. Sivertsen sees Luke's as artificially pieced together out of oral traditions. The pre-exilic series Levi, Simeon, Judah, Joseph consists of the names of tribal patriarchs, far more common after the exile than before, while the name Mattathias and its variants begin at least three suspiciously similar segments. Kuhn likewise suggests that the two series Jesus–Mattathias (77–63) and Jesus–Mattatha (49–37) are duplicates. The contradictions between the lists have been used to question the accuracy of the gospel accounts since ancient times, and several early Christian authors responded to this. Augustine, for example, attempted on several occasions to refute every criticism, not only because the Manichaeans in his day were using the differences to attack Christianity, but also because he himself had seen them in his youth as cause for doubting the veracity of the Gospels. His explanation for the different names given for Joseph's father is that Joseph had a biological father and an adoptive father, and that one of the gospels traces the genealogy through the adoptive father in order to draw parallels between Joseph and Jesus (both having an adoptive father) and as a metaphor for God's relationship with humankind, in the sense that God "adopted" human beings as his children. One common explanation for the divergence is that Matthew is recording the actual legal genealogy of Jesus through Joseph, according to Jewish custom, whereas Luke, writing for a Gentile audience, gives the actual biological genealogy of Jesus through Mary. This argument is problematic, however, because both trace their genealogy through Joseph. Eusebius of Caesarea, on the other hand, affirmed the interpretation of Africanus that Luke's genealogy is of Joseph (not of Mary), who was the natural son of Jacob, though legally of Eli who was the uterine brother of Jacob. Levirate marriage The earliest tradition that explains the divergence of Joseph's lineages involves the law of levirate marriage. A woman whose husband died without issue was bound by law to be married to her husband's brother, and the first-born son of a Yibbum was reckoned and registered as the son of the deceased brother (Deuteronomy 25:5 sqq.). Sextus Julius Africanus, in his 3rd-century Epistle to Aristides, reports a tradition that Joseph was born from just such a levirate marriage. According to this report, Joseph's natural father was Jacob son of Matthan, as given in Matthew, while his legal father was Eli son of Melchi