Cosmology and the Origin of Life *

We discuss some of the cosmological constraints on the evolution and persistence of life in the Universe and in hypothetical universes other than our own. We highlight the role played by the age and size of the universe, and discuss the interplay between the main-sequence stellar lifetime and the biological evolution time scale. The consequences of different versions of the inflationary universe scenario are described in the light of limits on the possible variation in the values of the constants of Nature. 1 Cosmology, Stars and Life Prior to the discovery of the expansion of the Universe there was little that cosmology could contribute to the question of extraterrestrial life aside from probabilities and prejudices. After our discovery of the expansion and evolution of the Universe the situation changed significantly. The entire cosmic environment was recognised as undergoing steady change. The history of the Universe took on the complexion of an unfolding drama in many acts, with ∗Invited Talk delivered at the Varenna Conference, The Origin of Intelligent Life in the Universe, 30th September 1998, Varenna.