3 - Evolution – Here and Elsewhere

Summary

This is where we switch from the geography of alien life to its biology – in other words from its distribution across the observable universe to its ‘nature’ in many senses of that word, including its chemical composition, its physical form, its means of acquiring energy, and, in some cases, its intelligence. For me, the nature of life beyond Earth is even more interesting than exactly which planetary bodies it inhabits, and many other scientists feel likewise. However, in moving from geography to biology things also become more controversial, because the so-called ‘sample size of one’ problem comes into sharp focus.