distorted the past. They highlighted the activities of the literate and could
say nothing about the history of the natural world or of anything that existed
before the invention of writing. The idea that history could only be based
on written documents created a sense of separation between human history
and the history of the natural world. Written evidence could also deceive.
Christian theologians, such as Eusebius of Caesarea (who died c. 340 C.E.),
used written evidence from the Old Testament to date the moment of creation
to about 4000 B.C.E. Their evidence-based calculations would dominate
Christian cosmology for 1,500 years.
From the 17th century, new evidence began to undermine this chronology.
Seventeenth-century geologists already doubted the traditional Christian
timescale of 6,000 years. For example, the ¿ nding of marine fossils in
mountains suggested that mountains had
once been under the sea, which suggested
they had been created over vast periods
of time.
In 1795, James Hutton (1726–1797) argued
that the Earth’s surface had been formed by
slow processes such as erosion and uplift,
acting over unimaginably long periods of
time. By his time, it was possible to generate relative dates for the Earth’s
history (saying what order things occurred in by using the fossils in different
strata), but he despaired of constructing an absolute chronology. As late as
the early 20th century, written records remained the basis for chronology.
When, just after World War I, H. G. Wells attempted a form of big history
in his Outline of History, he knew that he had no precise dates before the 1st
millennium B.C.E.
The situation was transformed in the middle of the 20th century by a second
“chronometric” revolution. The discovery of radioactivity provided the
crucial breakthrough. Marie (1867–1934) and Pierre (1859–1906) Curie
discovered radioactivity, and both eventually died of cancer caused by
handling radioactive substances. A New Zealand–born physicist, Ernest
Rutherford (1871–1937), showed that radioactive materials break down with
great regularity, so that in principle they could be used as clocks. In the 1950s,
The ¿ rst “chronometric”
revolution was the
appearance of writing,
about 5,000 years ago.