What major turning points changed it over time?

The core never changed; that is the point. The early milestones were about preserving the text, not revising it. Later splits and sects are departures from the original, not new versions of it.

D'Holbach's openly atheist System of Nature (1770); Darwin (1859); Marxist state atheism in the 20th century; the post-war secular humanist organizations; the 'New Atheism' wave after 2001; and the continuing rise of the religiously unaffiliated.

The coinage of the word (1869); its adoption by Victorian scientists; 20th-century philosophy sharpening the distinction between 'weak' agnosticism (I do not know) and 'strong' (no one can know); and the modern rise of 'spiritual but not religious' identities.

Nicaea and the creeds (4th century); the Great Schism between Catholic and Orthodox (1054); the Protestant Reformation (1517); the modern encounter with historical criticism and European secularization; and the 20th-century Pentecostal explosion that moved Christianity's center of gravity southward.

The Temple's destruction (70 CE) and the turn to rabbinic Judaism; the completion of the Talmud; medieval philosophy and Kabbalah; the 18th–19th-century Haskalah (Jewish enlightenment) and the Reform–Conservative–Orthodox division; the Holocaust; and the State of Israel (1948).

The early councils and the Theravada–Mahayana divergence; transmission to China (1st century CE) and Tibet (7th–8th centuries); the decline in India; colonial-era revivals in Asia; and the 20th-century spread to the West, including modern 'engaged Buddhism.'

The Upanishadic turn inward; the rise of bhakti devotion; the classical philosophical schools; the long encounters with Buddhism, Islam, and British rule; 19th-century reform (Brahmo Samaj, Vivekananda); and post-independence and diaspora Hinduism.

The founding of the Khalsa (1699); the scripture installed as Guru (1708); the Sikh empire under Ranjit Singh; British annexation of Punjab (1849); the Singh Sabha reform movement; the 1947 Partition dividing Punjab; and the 20th-century diaspora.

The Peace of Westphalia ending Europe's religious wars (1648); the First Amendment (1791); the French separation (1905); the secular constitutions of Turkey and India in the 20th century; and the late-20th-century religious revivals that put the model under strain.

The Renaissance; the Enlightenment; Humanist Manifesto I (1933), II (1973), and III (2003); the Amsterdam Declarations (1952, 2002, 2022); and the growth of humanist ceremonies — weddings, namings, funerals — as civil alternatives to religious rites.

1689, 1776, and 1789; the 19th-century reform era; near-collapse between the world wars; the post-1945 rights order; the market ('neoliberal') turn of the 1980s; the post-1989 high tide; and the present contest with resurgent nationalism and authoritarianism.

1792 and 1848; the suffrage victories (1893 onward); The Second Sex (1949); the second wave and its legal reforms; CEDAW (1979); the naming of intersectionality (1989); and #MeToo (2017).

1789; the 1848 'springtime of peoples'; the unifications of Italy (1861) and Germany (1871); self-determination in 1918; fascism's extreme nationalism and the Second World War; decolonization; and the nationalist revivals since 1989 and in the present decade.