So what is more impressive in human history—the innovations and changes or the enduring patterns and lasting features? At the level of personal history, most people have no doubt noticed the brevity and transience of life, marked as it is by childhood, coming of age, marriage, the birth of children, illness, decline, and death. Every culture has developed rituals to honor these changes. And yet we also recognize some enduring sense of self across the span of a life, some continuity, at least in memory, between the child and the elder.

Beyond our individual histories, however, our perception of change or continuity in the wider arenas of life surely depends on when we are living. During the long Paleolithic and Neolithic eras, few people were aware of major changes in the larger patterns of life. Of course, change happened: nomadic peoples settled down in villages; agriculture developed; cities arose; states and empires took shape; class structures evolved; patriarchy emerged more sharply defined. But few of these changes occurred quickly enough to be noticeable in a single lifetime. It is among the great contributions of world history to call attention to transformations of which we might otherwise be unaware. In the modern era, and certainly in our own time, the pace of change has dramatically accelerated. We have come to value, celebrate, expect, and promote change in ways that many of our distant—and not so distant—ancestors would find unimaginable.

What might we say about the balance of change and persistence in the era of second-wave civilizations? Clearly, there was much that was new, even if those innovations had roots in earlier times. The Greek conquest of the Persian Empire under the leadership of Alexander the Great was both novel and unexpected. The Roman Empire encompassed the entire Mediterranean basin in a single political system for the first time. Buddhism and Christianity emerged as new, distinct, and universal religious traditions, although both bore the marks of their origin in Hindu and Jewish religious thinking, respectively. The collapse of dynasties, empires, and civilizations long thought to be solidly entrenched—the Chinese and Roman, for example—must surely have seemed to people of the time to be something fearfully new.

But much that was created in the second-wave era—particularly its social and cultural patterns—has demonstrated an impressive continuity throughout many centuries, even if it also changed in particular ways over time. China’s scholar-gentry class retained its prominence throughout the ups and downs of changing dynasties into the twentieth century. India’s caste-based social structure still endures as a way of thinking and behaving for hundreds of millions of men and women on the South Asian peninsula. Although slavery gave way to serfdom in post-Roman Europe, it was widely practiced in the Islamic world and massively extended in Europe’s American colonies after 1500. In various expressions, slavery remained an important and largely unquestioned feature of all civilizations until the nineteenth century, and in a few places it still exists. Patriarchy, with its assumptions of male superiority and dominance, has surely been the most fundamental, long-lasting, and taken-for-granted feature of all civilizations. Not until recent centuries have those assumptions effectively been challenged, and even so, patriarchy has continued to shape the lives and the thinking of the vast majority of humankind. And many hundreds of millions of people in the twenty-first century still honor or practice religious and cultural traditions begun during the second-wave era.

Persistence and change alike have long provided the inextricable warp and woof of both individual experience and historical study. Each of us no doubt ponders the tension between them in our own lives. Untangling their elusive relationship has figured prominently in the task of historians and has contributed much to the enduring fascination of historical study.