Lumpers and splitters

Lumping and splitting refer to the rearranging of taxonomic groups of species.

The naming of a particular species should be regarded as a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be confirmed or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as the same species. When two named species are discovered to be of the same species, the older species name is usually retained, and the newer species name dropped, a process called synonymization, or convivially, as lumping. Dividing a taxon into multiple, often new, taxons is called splitting. Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognizing differences or commonalities between organisms.

The lumper/splitter problem occurs in disciplines where there is the need to create classifications and assign examples to them, for example schools of literature, biological paleo-species and so on. A "lumper" is an individual who takes a gestalt view of a definition, and assigns examples broadly, assuming that differences are not as important as signature similarities. A "splitter" is an individual who takes precise definitions, and creates new catagories to classify samples that differ in key ways.

Each approach has its well known problems. Lumping tends to create a more and more unwieldy definition, with members having less and less mutually in common. This can lead to definitions which are little more than conventionalities, or groups which join fundamentally different examples. Splitting often leads to "distinctions without difference", ornate and fussy catagories, and failure to see underlying similarities.

For example, in the arts, "Romantic" can refer specifically to a period of German poetry roughly from 1780-1810, and excludes the work of Goethe, who is, instead a "neo-classic" poet. In music it can mean every composer from Hummel through Rachmaninoff, plus many that came after.