Intersante and controversial topic, must in the past propitiated conflicts and heated discussions. I think his point is to emphasize that Judaism was first and that Christianity is a religious progressive of them.
Undoubtedly, this is the case, the history is organized of lesser quality, and although Judaism is an older religion and culture, it is still valid in a large part of the western Mediterranean. And Christianity in some way was able to inhabit races and places. Judaism was as closed in the Jewish families, the Christianity muted and opened to all humanity.