Excerpt from: “Why I am not a Christian” by Keith M. Parsons
Only one conclusion can be drawn from this discrepancy between the two supposed genealogies: both Matthew and Luke are determined to trace Jesus’s descent from King David. Indeed, they have to do so in order to maintain that he was the Messiah predicted by the Jewish prophets. But, it is quite clear that they had no evidence of the actual descent, so each simply invented a lineage to link him with Zerubbabel and thus with King David.
Needless to say, this problem of the irreconcilability of the two lineages has not gone unnoticed. So desperate did some Christian commentators become that they resorted to the claim that the two genealogies were not meant to be the same. Matthew’s family tree, they maintained, is that of Joseph, while Luke’s is that of Mary. In this way it was presumably hoped not only to solve the problem of the irreconcilable differences between the two genealogies but also to invest Mary as well as Joseph with Davidic ancestry. Unfortunately for them, however, the texts themselves are only too clear. Luke’s genealogy does not mention Mary’s name at any point but makes it quite plain that this is Joseph’s lineage (3:23) (Arnheim, 1984, p, 16).