The fossil evidence suggests that Homo
erectus originated in Africa, then dispersed into other regions. Geographic
differences are present, but these seem to reflect regional adaptations
and gene pools which would be expected given small populations living in
relative isolation. For a long stretch of Pleistocene time, the hominids
did not change much anatomically. Advances in cultural behavior probably
came slowly as well.
The following is a historical perspective on how Homo erectus has been defined:
The story of Homo erectus begins in southeast Asia, where the first
fossils were unearthed just over a century ago. The finder was Eugene Dubois,
a young Dutch anatomist. In 1891 Dubois' group of laborers dug a fine skullcap
from the banks of the Solo River at Trinil; they also located a nearby femur.
Dubois identified what he referred to as Pithecanthropus erectus :
a relatively smallbrained creature capable of walking bipedally. This combination
of features suggested that Pithecanthropus was neither an ape nor
fully human, but must constitute instead a stage or link in human evolution.
Additional Javanese material came from Sangiran. In 1936, Ralph von Koenigswald recovered a mandible and, in 1937, the first of several crania. One, known as Sangiran 2, was remarkably like that found by Dubois. An upper jaw with teeth and the rear portion of a cranium of another individual were picked up in 1938 and 1939. More fossils came to light after World War II. Establishing a reliable chronology for the geological sequence at Sangiran has been difficult, but several series of radiopotassium and fission-track dates are now available. There are some inconsistencies in these results.
Other sites in central and eastern Java have produced further discoveries, including a number of faceless crania from Ngandong, a single specimen from Sambungmachan, and a well-preserved brain case picked up at Ngawi in 1988. Along with the Trinil and Sangiran fossils, most of this material has been studied extensively. Recent dating suggests that the material from Java may date as early as 1.6 million years in age.
Other early finds of Asia Homo erects came from the famous cave of Zhoukoudian in China . Tragically, nearly all of these were lost mysteriously during World War II. However, plaster casts had been prepared, so that the anatomist Franz Weidenreich was able to describe these skulls, teeth, and limb bones in great detail. More recently, excavations at Zhoukoudian have yielded a few additional hominid remains, along with stone tools. There have also been significant finds at several other Chinese localities, including the Lantian sites of Gongwangling and Chenjiawo and Lontandong Cave at Hexian. These recent finds also suggest a relatively early occupation of Asia nearly 1.5 million years ago.
In 1960, parts of an important cranium were collected at Olduvai Gorge located in northern Tanzania. Given its thick brow and heavily constructed vault, this individual (called OH 9), which is probably male, was similar to several of the larger skulls from Asia. Comparisons to the Sangiran, Ngandong and Zhoukoudian crania demonstrate a likeness not only in general form but also in many anatomical details.
Since the 1970s, additional remains have been recovered from the Koobi Fora region on the eastern shores of Lake Turkana, in Kenya. These include a well-preserved cranium (KNM-ER 3733). On the basis of precise dating of volcanic tuffs interbedded with the lake sediments at Koobi Fora, these fossils are as much as 1.7 to 1.8 million years old. Like the Olduvai material, the ancient skulls from Koobi Fora are quite similar to Homo erectus from the Far East. Features of the face of KNM-ER 3733 set this hominid apart from earlier Homo as well as specimens representing Australopithecus. The brow ridge is prominent, but not as massive as that of some later Homo erectus. The forehead is low and the back of the braincase is "pointed".
More information about body size and proportions can be obtained from another almost complete skeleton discovered on the west side of Lake Turkana. The bones represent a young male. The stature of this individual is about 160 cm, although the boy certainly would have grown further, perhaps to a height of more than 180 cm. This translates into an adult at least 6 feet in height. This individual was tall and thin relative to other early hominids. In other words, he was lean similar to people living in that part of Africa today. Mechanics of his leg and pelvis indicate he was very capable of efficient bipedal movement; in fact this is a superior engineering for bipedality to that of modern humans who have had to sacrifice this efficiency to gain a larger brain size.
Very recently, a mandible with teeth was discovered during excavations at Dmanisi in Georgia. This jaw appears to shed new light on the earliest people of Europe and western Asia. The Dmanisi specimen certainly shares some features with Homo erectus, and it may be close to, or even greater than, 1.0 million years in age. There is a claim that it may date to as early as 1.5 million years ago.
It is clear that the later archaic Homo sapiens populations of Europe and Africa are more closely related to us than is Homo erectus in brain size. While Homo erectus fossils are scant in Europe, the presence of Homo erectus is based on archaeological evidence to a large degree. Fossils representing Homo erectus do not turn up in the European record until later in the Middle Pleistocene. Important discoveries have been made at Mauer in Germany, Petralona in Greece, Arago Cave in France, and Vertesszollos in Hungary. Field work at Bilzingsleben in Germany and at caves in the Sierra de Atapuerca in Spain turned up a number of cranial fragments, lower jaws, and partial limb bones. Dating is very approximate, but even the Mauer mandible, perhaps the oldest of the European finds, may be less than 600,000 years old. Some of the specimens resemble Homo erectus in a general way. However, these hominids share key features with later people and may represent populations that were more advanced than Homo erectus. This evidence suggests that Europe was populated by a later migration than seen in Asia. There is some continuity that can be seen from African Homo erectus and one of the earliest later erectus or Archaic Homo sapiens from Steinheim.
If groups of Homo erectus moved from Africa into the Levant and across south Asia to the Far East about 1.5 million years ago, and if the species then continued to expand its range to other regions, how did it evolve? Paleoanthropologists debate the nature of change in Middle Pleistocene populations and the emergence of more advanced humans. According to one scenario, there was evolutionary continuity in many areas. This view assumes that changes occurred slowly and that populations of late Homo erectus were succeeded, in an unbroken progression, by more modern hominids.
Other paleoanthropologists prefer to envision multiple species (not simply subspecies) in the Pleistocene record. They see evidence that Homo erectus develops into different populations. The older African material,Homo ergaster, is viewed as responsible for the initial spread out of Africa. Within Africa, this group evolves independently from other regions into later hominids that eventually become modern Homo sapiens.