HOMO SAPIENS

genus and species to which all modern human beings (Homo sapiens sapiens) belong and to which are attributable fossil remains of humans perhaps as much as 400,000 years old. Homo sapiens is distinguished from other animals and from earlier hominid species by characteristics and habits such as bipedal stance and gait, brain capacity averaging about 1,350 cubic cm (82 cubic inches), high forehead, small teeth and jaw, defined chin, construction and use of tools, and ability to make use of symbols such as language and writing. Some of these features were possessed by the immediate ancestor, Homo erectus; but in the aggregate they are characteristic only of Homo sapiens. Homo sapiens, man the wise, is the only currently existing species of the genus Homo. It is difficult, if not impossible, to follow the evolutionary steps that led to this distinction in the fossil record. Charles Darwin himself defined the problem. In a series of forms graduating insensibly from some ape-like creatures to man as he now exists, he wrote in The Descent of Man, it would be impossible to fix on any definite point when the term man ought to be used. One of the things that makes discovery of a point of distinction so difficult is that H. sapiens is the product of an evolutionary process called mosaic evolution, which postulates that humans did not evolve smoothly as a species but that various populations evolved at different rates according to environmental and genetic circumstances. And, because fossils are the remains of individuals, who differ even within populations, one fossil alone or even a few do not adequately describe how a population may have evolved. The time when the early forms of H. sapiens were evolving has now been fixed as the late Middle Pleistocene epoch, about 100,000 to 250,000 years ago, perhaps even as long as 400,000 years ago. Before the principle of mosaic evolution was accepted, there were several types within the genus Homo that were thought to be distinct enough to warrant being classified as separate species. The best known of these is Neanderthal, long classified as H. neanderthalis, who possessed a combination of cranial, dental, and postcranial features that appeared to separate him from H. sapiens. Subsequent research has led many workers to classify Neanderthals as a human subspecies (Homo sapiens neanderthalensis), although controversy remains about their classification. Another example of a related species, or possibly an intermediate form, is indicated by fossil remains of the teeth of a child and a broken adult occipital bone (the bone at the back of the skull) in a site known as Vrtesszollos in Hungary. With an estimated cranial volume of 1,400 cubic cm and various other characteristics, this fossil is in some respects quite modern, and it was agreed that it originated from H. erectus but might well be the beginning of a progressive evolutionary line. It has therefore been classified as Homo (erectus seu sapiens) palaeohungaricus to indicate that it is probably an intermediate form. Other probable intermediate forms have been discovered at Swanscombe in North Kent, England; at Steinheim site, near Stuttgart, Germany; at Petralona in northeastern Greece; and at Arago cave near Tautavel in southern France. In Africa, along the Omo River in southern Ethiopia, two skulls and a large number of limb bones that are regarded as early modern H. sapiens have been recovered. Other early modern humans have been found in Africa at the Laetoli site in Tanzania and at the Border Cave site between Swaziland and the black state of KwaZulu in South Africa. These discoveries represent some of the earliest-known fossils (more than 100,000 years old) of modern H. sapiens and lend support to the theory that all modern humans have a common origin in Africa.