I wondered if you knew of any resources that might help on explaining why the genealogies in Matthew and Luke are different, especially why they have a different number of generations.
I think it comes down to different ways in which different cultures define the family. Judaism was a tribal society, where the family consisted of extended families in larger, concentric units. As one scholar explains:
"Josh 7:14-18 (cf. Judg 17-18) has become the locus classicus for understanding the use of the Hebrew words for family: sebet (‘tribe’), mispaha (‘clan’), and bayit (‘house’; or, better, bet-ab, ‘fathers' house’). With the help of ethnographic studies and archaeological research, these terms, especially the last two, can be understood as 'kinship group' and 'family household,' respectively," R. Hess & M Carroll, eds. Family in the Bible: Exploring Customs, Culture, and Context (Baker 2003), 35.
We, in the contemporary West, think of a family as a serial nuclear family. Hence, we see discrepancies between the two synoptic gospels because we come to the text with alien presuppositions.
But the Jews had a more flexible definition of kinship and ancestry. Tom Wright has briefly commented on this difference (see below).
I should add that numerology is a factor in both genealogies. This is explicit in the case of Matthew.
But Bauckham has argued that septunarian numerology is also shaping the Lucan genealogy (Cf. Jude and the Brothers of Jesus, chap. 7).
This doesn't mean that either of them concocted the materials. Rather, given the flexibility of family trees in Judaism (see my previous email), they used numerology as a selection-criterion, choosing the historical links they needed (while omitting others) to trigger literary allusions and historical associations with the past. I discuss this in my review of TET.