There are many reasons Biblical genealogy is important. First, why does anyone study genealogy? It gives the family history. In the case of the Bible it would be the history of humankind. Who were our first parents? How long ago did they live? What experiences did they have? Who were their children? God “has made of one blood all nations of men to dwell on all the face of the earth.” (Acts 17:26) In Genesis 5 we get a connected history of the first 1656 years of human history through genealogy.
As a side point, science has confirmed we all came from the same mother. The mitochondria DNA in the cell is only passed down from mother to daughter and all women have the same mitochondrial DNA. The science community calls this female ancestor “mitochondrial Eve.” DNA-sequencing of the human Y-gene which is passed down only from father to son also points to one common ancestor for men also. The science community calls this male ancestor “Y-gene Adam.”
Secondly, we can trace the faith line of Mary and Joseph and see that Jesus is the promised Messiah. Luke 3:23-38 records the genealogy of over 4,000 years from Jesus to Adam. God honored Abraham as the father of the faithful, and he was told through his posterity all the families of the Earth would be blessed. (Genesis 22:17-18) The faith line of the Messiah was narrowed down to the tribe of Judah (Genesis 49:9, 10). Several centuries later the faith line was narrowed down to a family. David was promised that the Messiah would be one of his descendants. (1 Chron. 17:11-14) That’s why Jews kept an accurate family history.
Both Mary and Joseph were descendants of David. They were traveling to Bethlehem to register for taxes. “And Joseph also went up from Galilee out of the city of Nazareth into Judea unto the city of David which is called Bethlehem; because he was of the house and lineage of David” (Luke 2:4) Before Jesus’ conception Mary was told, “He shall be great and shall be called the Son of the Highest and the Lord God shall give unto him the throne of his father David.” (Luke 1:32) David truly was one of Jesus’s Fathers.
God keeps his promises. The promises made to Abraham, Judah and David are fulfilled in Jesus, the world’s redeemer. In verse 33, the angel gave Mary another promise about her baby. It was “he shall reign over the house of Jacob forever and of his kingdom there shall be no end.” We are yet waiting for its fulfillment.