Origins and History, HISTORICAL CONTEXT:
Natural History and Human History, 15 Billion -- 5 Thousand Years Ago
*excerpted from Kevin Reilly's Worlds of History: A Comparative Reader (Bedford/St Martin's: 2000) pp.1-6.
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The subject of history is change. The context of history is place and time. While the "place" of world history is the entire planet, the "time" can vary considerably. In this chapter, you will read abbreviated world histories that focus on time periods long past. We begin with the largest canvas possible: the history of the Earth. Next we examine the history of life on Earth, then the history of human life. The first three selections are not world histories in the conventional sense; that is, they are not histories of human activity. Rather, they are histories of the world and of important changes in the world.
  The final two selections are histories of human activity, though, again, of time periods long past. The selection by Fowler addresses the earliest stage of human activity: hunting and gathering. It points to a particular activity -- weaving -- that was not previously associated with our hunting-gathering ancestors. Prior to this discovery, it was believed that weaving first appeared in humankind's next development stage, the invention of agriculture. The last selection by Wilford concerns the span of history since the beginnings of agriculture. Here, too, recent research may force us to revise our thinking: Agriculture may have begun earlier in the Americas than has previously been thought.
  This chapter covers vast spans of time for two reasons: First, it is always humbling to realize, in the grand scheme of things, how briefly we humans have lived and acted upon our planet. Second, we are forced to wonder what we might miss when we study, as we do in most history courses, only the last five or ten thousand years of planetary history. After reading these selections, you might ask, what is the proper subject of world history?

Historians try to date events not because the dates have any meaning in and of themselves, but in order to compare two or more events. If we had only a single date, it would tell us nothing. It is always in comparing and gaining perspective that true insight comes. By comparing dates, we can determine whether events occurred simultaneously, whether two events were near or far in time, and whether change was gradual or fast.
  To make these judgments, we need to date as many events as possible and then chart the events on something that will clearly show their relationships in time. In the first selection, Carl Sagan uses a calendar and a clock to show the relationships of certain events in the history of the Earth. More frequently, historians use time lines to chart change. Time lines function as chronological yardsticks or rulers, with events being placed at appropriate intervals based on the "measure" used; for example, days, weeks, or years.
  Time lines, as useful as they are, are specific to the span of time they measure. There can be no single time line for world history. Time lines are tools constructed to answer particular questions. Throughout the chapter, I ask you to create time lines of your own.

Carl Sagan, From The Dragons of Eden: Speculations on the Origins of Human Intelligence

Introduction and Instructions: The astronomer Carl Sagan was one of the great popularizers of science in the twentieth century. In this selection from one of his many books, he finds a simple way to demonstrate the vastness of Earth's history. He plots the history of the planet on a calendar for a single year and, in this framework, he notes that the first humans appeared at 10:30 P.M. on New Year's Eve. What does this approach show you about the relationship between the history of the Earth and the history of humankind?
  Transfer some of the important dates of Sagan's calendar to a time line. Draw a 12-inch line horizontally on a piece of paper, marking inch designations. The Big Bang is at the left end (0), and today is at the right end (12). Your world history course will deal only with the last hour on Sagan's log of events £or December 31. Where would that be on your time line? Where would you place your own life on this time line? Where would you place the life of one of your grandparents? What is the major disadvantage of a time line drawn to this scale? What is its advantage?

The world is very old, and human beings are very young. Significant events in our personal lives are measured in years or less; our lifetimes in decades; our family genealogies in centuries; and all of recorded history in millennia. But we have been preceded by an awesome vista of time, extending for prodigious periods into the past, about which we know little -both because there are no written records and because we have real difficulty in grasping the immensity of the intervals involved.
  Yet we are able to date events in the remote past. Geological stratification and radioactive dating provide information on archaeological, paleontological, and geological events; and astrophysical theory provides data on the ages of planetary surfaces, stars, and the Milky Way Galaxy, as well as an estimate of the time that has elapsed since that extraordinary event called the Big Bang -an explosion that involved all of the matter and energy in the present universe. The Big Bang may be the beginning of the universe, or it may be a discontinuity in which information about the earlier history of the universe was destroyed. But it is certainly the earliest event about which we have any record.
  The most instructive way I know to express this cosmic chronology is to imagine the fifteen-billion-year lifetime of the universe (or at least its present incarnation since the Big Bang) compressed into the span of a single year. Then every billion years of Earth history would correspond to about twenty-four days of our cosmic year, and one second of that year to 475 real revolutions of the Earth about the sun. [Following] I present the cosmic chronology in three forms: a list of some representative pre-December dates; a calendar for the month of December; and a closer look at the late evening of New Year's Eve. On this scale, the events of our history books -even books that make significant efforts to de-provincialize the present -- are so compressed that it is necessary to give a second-by-second recounting of the last seconds of the cosmic year. Even then, we find events listed as contemporary that we have been taught to consider as widely separated in time. In the history of life, an equally rich tapestry must have been woven in other periods -for example, between 10:02 and 10:03 on the morning of April 6th or September 16th. But we have detailed records only for the very end of the cosmic year .
  The chronology corresponds to the best evidence now available. But some of it is rather shaky. No one would be astounded if, for example, it turns out that plants colonized the land in the Ordovician rather than the Silurian Period; or that segmented worms appeared earlier in the Precambrian Period than indicated. Also, in the chronology of the last ten seconds of the cosmic year, it was obviously impossible for me to include all significant events; I hope I may be excused for not having explicitly mentioned advances in art, music, and literature or the historically significant American, French, Russian, and Chinese revolutions.
  The construction of such tables and calendars is inevitably humbling. It is disconcerting to find that in such a cosmic year the Earth does not condense out of interstellar matter until early September; dinosaurs emerge on Christmas Eve; flowers arise on December 28th; and men and women originate at 10:30 P.M. on New Year's Eve. All of recorded history occupies the last ten seconds of December 31; and the time from the waning of the Middle Ages to the present occupies little more than one second. But because I have arranged it that way, the first cosmic year has just ended. And despite the insignificance of the instant we have so far occupied in cosmic time, it is clear that what happens on and near Earth at the beginning of the second cosmic year will depend very much on the scientific wisdom and the distinctly human sensitivity of mankind.

Pre December Dates (approximate)

Cosmic Calendar / December

Cosmic Calendar / December 31, last 12 hours