Proteins are essential building blocks of living cells; indeed, life can be viewed as resulting substantially from the chemical activity of proteins. Because of their importance, it is hardly surprising that ancestors for most proteins observed today were already present at the time of the 'last common ancestor', a primordial organism from which all life on Earth is descended. How did the first proteins arise? How can we bring a taxonomic order to the diversity of forms that evolved from them? These two questions are at the center of our scientific efforts, on which we bring to bear methods in bioinformatics, protein biochemistry and structural biology.