Computer printout of mathematical rules behind the Daisyworld model, by James Lovelock, 1981. Annotation in blank ink reads 'JELC. 1981'. Measurement is for item folded, when open measures 1680 mm.

This print-out shows the mathematical rules devised by Lovelock that run the virtual environment Daisyworld. It was the first mathematical model of a world where the environment and organisms evolved together by natural selection. Lovelock developed this program to answer the criticism that his Gaia hypothesis – which describes the Earth as a self regulating system that maintains conditions suitable for life – was incompatible with Darwin’s theory of evolution by natural selection.