Introduction to molluscan taxonomy 4) Taxonomic history

Taxonomy is the science of the classification of all organisms. The term is derived from two Greek words, meaning arrangement and law, and was proposed by de Candolle in 1813. It is built upon the basic studies of morphology, physiology, ecology and genetics.

Since the time of Linnaeus the number of known species of animals has increased enormously. Including sub-species there are probably more than 2 million named forms and new ones are being described at the rate of 10,000 per year. About 80,000 molluscs have been described.

The history of taxonomy goes back certainly to the ancient Greek scholars, notably Hippocrates (460-377 B.C.) and Democritus (465-370 B.C.) who included animals in their studies, however it was Aristotle (384-322 B.C.) who first brought together the knowledge of his time and formulated it into the beginings of a science. He did not propose a formal classification, but provided the basis for one in his statement that "animals may be characterised according to their way of living, their actions, their habits and their bodily parts". The Aristotelian philosophy - it can scarcely be called a system - sufficed for students of animals for nearly two thousand years. It is only in the works of the immediate predecessors of Linnaeus that we find any attempt at a scientific classification.

Of all the earlier authors, the one that had the greatest influence on Linnaeus was John Ray (1627-1705)> who recognised the difference between the genus and the species. The type of taxonomy that is based on the study of local faunas reached its peak in the great Swedish naturalist Linnaeus (1707¬1778) whose work so influenced subsequent students that, with much justification he has been called the father of taxonomy. In the 10th. edition of his great work 'Systeme Naturae' (1758) the binominal system of nomenclature was for the first time consistently applied to animals, and this work became the foundation of systematic zoology. In addition to his nev,r system of nomenclature, the work of Linnaeus was characterised by clear-cut species diagnoses and by the adoption of a hierarchy of higher categories2 genus, order, class. It dominated taxonomy for the next century and most of the essentials of the Linnaean method are still the components of modern taxonomy.

Evolutionary thought, already widespread in the 18th. century (Buffon, Lamarck and many others), was to play a large part in the development of taxonomy, as a result of the stimulus it gave to biological work and the presentation to the Linnaean Society in 1858 of the joint views of Charles Darwin (1809-1882) and Alfred R. Wallace (1823-1913) on the theory of natural selection in one of the most dramatic episodes in the history of science. The publication of Darwin's 'On the Origin of Species' (1859) lead to the search for 'missing links' and 'primitive ancestors', efforts which, although mainly unsuccessful, were not wasted because they resulted in the discovery of many new life forms. Not only were new species and genera discovered daily, but with reasonable frequency even new families or orders, and the result of such exciting discoveries attracted the keenest minds to the field of taxonomy.

The wealth of nature is not however inexhaustible and the period of major new discoveries in the higher animals was over well before the end of the 19th. century. It was followed by the most recent phase in the history of taxonomy, the study of evolution within species. The typological concept of the species was abandoned and replaced by a dynamic, polytypic concept. Interest reverted to the study of variation within populations and the slight differences between adjacent populations. This type of study was commenced in the second half of the 19th, century and amongst malacologists may be mentioned particularly in this connection, Kobelt and Gulick the Sarasim brothers and Crampton, whose biometrical studies in the local geographical variations in the genus Partula (1916) have become classical.

The tqxonomic work of the present century is a continuous refinement of the methods and concepts developed in the 19th. Current taxonomy is customarily referred to as the new systematics (Huxley, 1940), but it must not be forgotten that its roots go back to the pioneer work so well done by the great naturalists of the first half of the 19th. century.

Further reading

Huxley, J. S., 1940. The New Systematics. Clarendon Press, Oxford.

Mayr, E., 1942. Systematics and the Origin of Species. Columbia University Press, New York.

Ramsbottom, J., 1938. Linnaeus and the Species Concept. Proc. Linn. Soc., London, 150th. Session.

Raven, C. E., 1942. John Ray, Naturalist. His Life and Works. Cambridge University Press.

Crampton, H. E., 1916. Carnegie Inst. Wash. Pub. 228, and 1932, ibid 410.


T. Pain