Origins of Judaism
For centuries, the traditional understanding has been that Judaism came before Christianity and that Christianity separated from Judaism some time after the destruction of the Second Temple in 70 CE. Starting in the latter half of the 20th century, some scholars have begun to argue that the historical picture is quite a bit more complicated than that. In the 1st century, many Jewish sects existed in competition with each other, see Second Temple Judaism. The sects which eventually became Rabbinic Judaism and Early Christianity were but two of these. Some scholars have begun to propose a model which envisions a twin birth of Christianity and Judaism rather than a separation of the former from the latter. For example, Robert Goldenberg (2002) asserts that it is increasingly accepted among scholars that "at the end of the 1st century CE there were not yet two separate religions called "Judaism" and "Christianity"".
Daniel Boyarin (2002) proposes a revised understanding of the interactions between nascent Christianity and nascent Rabbinical Judaism in Late Antiquity which views the two religions as intensely and complexly intertwined throughout this period.
Islamic schools and branches
In addition to these two main branches, many other opinions also formed regarding succession to Muhammad. The first centuries of Islam gave rise to three major sects: Sunnis, Shi'as and Kharijites. Each sect developed distinct jurisprudence schools ("madhhab") reflecting different methodologies of jurisprudence ("fiqh"). The major Sunni madhhabs are Hanafi, Maliki, Shafi'i, and Hanbali. The major Shi'a branches are Twelver (Imami), Ismaili (Sevener) and Zaidi (Fiver). Isma'ilism later split into Nizari Ismaili and Musta’li Ismaili, and then Mustaali was divided into Hafizi and Taiyabi Ismailis. It also gave rise to the Qarmatian movement and the Druze faith. Twelver Shiism developed Ja'fari jurisprudence whose branches are Akhbarism and Usulism, and other movements such as Alawites, Shaykism and Alevism. Similarly, Kharijites were initially divided into five major branches: Sufris, Azariqa, Najdat, Adjarites and Ibadis. Among these numerous branches, only Hanafi, Maliki, Shafi'i, Hanbali, Imamiyyah-Ja'fari-Usuli, Nizārī Ismā'īlī, Alevi, Zaydi, Ibadi, Zahiri, Alawite, Druze and Taiyabi communities have survived. In addition, new schools of thought and movements like Quranist Muslims, Ahmadi Muslims and African American Muslims later emerged independently.