Systematics: use of protein nearest neighbour frequency distribution as an objective key.

Although it is one of the oldest of modern disciplines, systematics has always been a science practised in a highly personalised and subjective way because of the need to rely on morphological characteristics of the living organisms, as well as the fossil remains, for their classification. Recent studies on the amino acid nearest neighbours, however, enable one to have an objective key for classifying organisms as well as their relationships.