Sir — Although your Millennium Essays focus on events in the past 1,000 years, it is easy to lose perspective when analysing time-windows much greater than our life-span. Our brains are not adapted to think in vast time-frames. So it may be helpful to take a bird's-eye view of our past millennium by using a series of time-windows — each one-hundredth the size of the previous one — to extend the analysis deeper in time.
In the largest time-window imaginable, comprising tens of millions of millennia, the past millennium doesn't show up. This window places the formation of Earth and the emergence of life in perspective: if the event creating our present Universe (the Big Bang) occurred around 15.5 million millennia ago, the development of life on Earth represents about 25% of the history of our Universe.
One per cent of this large window produces a second time-window covering the past 200,000 millennia, in which evolved extant animals and plants, primates and, finally, hominids.
In the third window, spanning 2,000 millennia, human invention starts to become apparent. Stone tools were used during the first half and fire was domesticated around the halfway point. These preceded the formation of the oldest-known fossils of Homo erectus, showing that creativity, technology development and invention were possessed by at least some of the australopithecine and other hominids long before H. sapiens appeared. Human creativity developed slowly, leaving the earliest paintings as evidence at the end of this window. This time-window saw the extinction of many other creatures (including all hominids except H. sapiens) — some caused by the sophisticated traps and projectiles made by H. sapiens.
The fourth time-window, using a 20-millennia lens, shows that both extinctions and human creativity continued to accelerate. Humans were weaving clothes at the beginning of this period, before the last ice age, by the end of which plants and animals were domesticated. This led to the development of agriculture about 10 millennia ago. The development of ceramics, the wheel, iron, bronze, steel and written documents followed at ever-shorter intervals. The use of script gives us a direct view on the thought processes of Homer, Lao-Tse, Buddha, Aristotle, Christ, Ptolemy, Muhammad and many others. These scripts show that human emotion did not differ significantly then from that experienced today.
Five per cent of this 20-millennia time-window focuses on the past millennium. The main feature of this millennium seems to have been the emergence of the scientific method. Science, defined as the method that subordinates theory to experimental results, was pioneered by Galileo and has been widely accepted as a superior form of thought only during the past two centuries. An interesting aspect is the shift of creative power from China to the West as the nationalistic and xenophobic policies of the Ming dynasty, started by Chu Yuan-chang in 1368, hindered commerce and the expansion of creativity in China. I detect a pause in the growth of creativity in the Christian world, spanning the first millennium ad (after Ptolemy and the Roman Emperor Julianus) to the Renaissance, overlapping with bursts of creativity in the Islamic world.
The past millennium shows no sign that the exponential expansion of human mental capabilities has stabilized. Evolution of other animal species, however, suggests that exponential evolutionary development of behavioural or morphological traits eventually stops. Even human creativity may start to do so in the third millennium ad.