Box 2A Humans and geological time

The time for which humans have lived on Earth is relatively insignificant on a planetary time-scale. This can be illustrated by shrinking the Earth's historical 4600 million years into the span of a single year, with the present day being midnight on 31 December.

On this scale the oldest rocks were formed on 25 February, the first multi-cellular organisms appeared on 29 October and the first plants started growing at the beginning of November. By 30 November the current composition of the atmosphere had nearly been reached (with 90 per cent of its present oxygen level). The rest of evolution is an ever-accelerating spiral: the first mammals appearing in mid-December; the first primates appearing on December 29 and the first Homo habilis emerging at 6 pm on December 31. The Lascaux caves were painted one and a half minutes before midnight while the industrial revolution is only two seconds old.

These two seconds represent the period of time over which humans have carried out most of the exploitation of natural resources relative to the age of the Earth (that is, during the past few centuries). This perspective allows a better understanding of the rapidity of this exploitation with respect to the slow accumulation of natural resources over hundreds of millions of years of geological time.