In eighteenth-century Europe the age of the Earth was computed from biblical genealogies, and Archbishop Ussher's date of 4004 BCE was widely accepted. Since every geological formation had to fit inside six thousand years, they were explained by sudden catastrophes — above all Noah's flood.

James Hutton, a farmer and physician from Edinburgh, developed another proposal by watching how soil eroded on his fields and where the sediment carried by streams went: the processes at work today, given enough time, suffice to explain all geological structures. Erosion lowers mountains, sediment accumulates in the sea, the Earth's heat turns that sediment into rock and lifts it; the cycle begins again. This principle of present causes is the core of what Lyell would later systematise as uniformitarianism.

The evidence came in 1788 at Siccar Point on the Scottish coast. Arriving by boat with his friends John Playfair and James Hall, Hutton pointed to a surface where horizontal younger strata rest on nearly vertical older ones. This 'unconformity' said that the vertical layers had first been laid down flat, then folded and raised, then eroded, before new sediment accumulated above — several complete cycles, one on top of another. Playfair wrote that the mind grew giddy looking so far into the abyss of time. The sentence from Hutton's 1788 paper is famous in the history of science: we find no vestige of a beginning, no prospect of an end. Deep time meant that seventy years later Darwin found the calendar evolution required already prepared.