Over two hundred years ago Linnaeus, the father of taxonomy, 5orsystematics as he called it, initiated the practice of giving each species in nature an italicized double name, or binominal, one of which was Homo sapiens. The first word is the name of the genus and the second that of the species itself. In the species Homo sapiens he included all living peoples. At that time no fossil men bad been discovered, and the genus Homo had therefore but a single species.
Linnaeus used only one word to designate biological units smaller than the species: variety. At that time the concept had not yet arisen that the unit of inheritance and evolution is the population to which an individual belongs rather than the individual himself, and the exact meaning ofvariety was not clear. In recent years taxonomists, in reviewing the nomenclature of species, have found that many units given specific rank in the past were subspecies, or geographical races, of larger units, and that what had been called varieties were races of one magnitude or another, or even individual variants.
In order to obtain material for classification, zoologists were kept busy collecting skins and skulls of many kinds of animals, and paleontologists removing bones, teeth, claws, and shells of ancient animals from the ground. Rarely did the paleontologists have whole skeletons to work with; and even when they did, characteristics studied by zoologists, such as hair form and color, skin structure, and the number of mammary glands, could not be determined except in a very few cases, as when mammoths were found frozen in the ground.
Whereas zoologists could collect large numbers of contemporary specimens, paleontologists sometimes possessed only unique specimens, which had to be related to others from different times and different places. Often the time gap between apparently related specimens was so great that it was unlikely that they could have belonged to a single species. Being cautious men, most paleontologists considered it more conservative to give separate generic names to unique or rare fossils of different periods than to assume their identity, particularly when in living animals such as the sheep and goat, which belong to different genera, the only difference visible in the skeleton is the relative lengths of the segments of the forelimb. Paleontologists therefore formed the habit of giving new and unique specimens separate generic names, setting aside the finer classification of related species until more bones had been found. When, in the second half of the nineteenth century, paleontologists and archaeologists began turning up the bones of fossil men, some of them applied this practice to the much more limited field of anthropology, and we find such designations as Pithecanthropus erectus, Sinanthropus pekinensis, and more recently, Atlanthropus mauretanicus tagged to specimens some of which differ from one another no more than do individuals in the living species.