Why the need for geneology? To the Hebrews, it was a way to trace their "uniqueness" as compared to the "outsiders", if one views Adam as the frist prototypical "hebrew".
You take away the Messiah in the "hebrew" sense, which got downplayed as time when on anyways.
I think you may detect the contradiction between those two statements, PSacramento. If the genealogies were retained in the Christian writings because they lent credibility to the messianic claim of Jesus of Nazareth from the Hebrew perspective then it does not follow that the Hebrew perspective would be later downplayed. It sounds too much like sucking people into listenting to The Truth by starting with a lie.
Here's the upshot. Ready? Fundamentalist Christian groups, and I will include the Watchtower as much as they would object, look down upon what they call cafeteria Christians precisely for this reason. Christianity is based 100% (one hundred percent) on the Bible, there is no other source. But people who consider themselves non-fundamentalist Christians will accept less than 100% of the Bible as fact. Rejection of the Adam and Eve story verbatim when it has been presented as fact together with the genealogy of Jesus of Nazareth, also presented as fact, is rationalisation of one's faith, picking and choosing between what is credible to him and what is not.
I agree, the Genesis story is not credible. It crumbles under the weight of massive contradictory evidence. But I also agree that the very basic tenets of Christianity fall apart without it, and it is for this reason I am not a Christian.