The Birth of Christ brackets and anchors this annotated time line because it is, in itself, the core “story” of humanity, and the single most important and influential factor in all of human history. The long narrative of the Jewish people and of the Jewish/Christian God’s inexorable and unceasing program of reconciliation for that “stiff necked people” (and ultimately for all people) to regain His fellowship and grace, crescendoed in the incarnation of the “logos of God”, by way of the man/God, Jesus the Christ and His ultimate crucifixion, and subsequent atoning resurrection (by which He overcame the spiritual death of selfish mankind by His personal physical death, i.e. He “trampled on death with death and on those in the tombs He bestowed life”).
That crescendo event stimulated the development of the “Jewish Sect of the Nazarene”, and the sect of the Nazarene grew into the nascent Christian church which continued to grow and expanded beyond Judaism into “the gentile world.” The growth of the nascent Christian Church in turn, led to the Christianization of the greater Mediterranean world (and ultimately to all of Europe and much of Asia and later to the American continents). The remarkable expansion of Christianity inexorably led to the subsequent human advances of the Roman Catholic Scholastic Movement (in the 12th and 13th centuries). The nascent scholastism of western Europe in turn spawned both the western scholastic movement of Humanism (in the 13th through the 15th centuries) and western Religious Reformation (of the 16th and 17th centuries). The combined interactions of the Scholastic Humanistic Movement and the Religious Reformation (destructively and constructively) spawned the subsequent parallel and simultaneous ages of Exploration (and Imperialism) and of the western Enlightenment which was spread around the globe by western Imperialism, for the better and for the worse (and it was definitely both better and worse in many specific instances). It was in turn the western Enlightenment which spawned the rise of the modern western democracies and produced the first and second Industrial Revolutions, the consequences of which yielded the Information Age and the entire modern world, such as it is.
For better or for worse, and despite the disputations and denials of many “modern” academics and self appointed anti-Christian iconoclasts, and social change agents, the birth of Christ WAS (for the better or for the worse depending on one’s point of view) the single most import factor, and the focal turning point in the development of the great human narrative of the last 10,000 years of human history.