Terrestrial biological evolution and its implication for SETI

A frequent opinion among biologists upholds that biological evolution is contingent and, consequently, that man's apparition is a random event of very small probability. We present various arguments against this view, based on chemistry, molecular biology, evolutionary convergences, the existence of physical constraints on the structure of living beings, and the evidence of acceleration in the evolution of many features, e.g. brain size, over geological times. Taken together they suggest that “laws” of evolution exist and may have a universal validity. We extend this view to the evolution of “intelligence”. We show that it is an essential aspect of biological evolution and that human cultural evolution is just another aspect of it. Finally, we argue that brains more complex than the human brain are conceivable, endowed not merely with quantitatively better functions but with qualitatively higher cognitive abilities, of the kind found in the transition from, say, dog to man. This thesis predicts that the usual concept of advanced civilizations merely separated by huge distances is too restrictive. It favours a different concept, in which the separation results predominantly from cognitive, i.e. temporal factors. This idea, far from being discouraging, offers a stimulating solution to Fermi's paradox and opens new ways to SETI.