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Soon after 1.8 million B.P. in Africa and nearly as long ago in Asia and Europe, an acceleration of human evolution took place. Many paleoanthropologists believe that all of the hominids that follow Homo habilis and predate Homo sapiens —from after 1.8 million B.P until about 300,000 B.P. or even later—belong to a single species: Homo erectus. Recent discoveries have convinced others that this period of human evolution presents us with a number of related, but more or less geographically separate, species. Homo rudolfensis & ergaster in Africa Homo erectus in central and east Asia Homo antecessor in Europe.
Genus Homo
Homo Erectus
Soon after 1.8 million B.P., a new form of hominid appeared in the fossil record of eastern Africa. The cranium of Homo erectus was quite different from that of its evolutionary antecedent, Homo habilis. The back, or occipital , portion of the erectus skull is rounder that that of habilis , with a much larger area for muscle attachment. Cranial endocasts of a number of Homo erectus specimens shows intriguing similarities to the modern human brain. A massive ridge of bone called a supraorbital torus , which is present in the skulls of all ape species and is generally absent in the modern human form. They walked upright, in a manner similar, if not identical, to that of modern human beings.
Issues and Debates
Human children are utterly dependent on adults to satisfy all their needs for a very long time. The term altricial is used to characterize baby birds who are completely dependent on their parents for fulfilling their needs. Human babies are said to be secondarily altricial. An additional hypothesis holds that one of the key changes that characterized ancient hominids from Homo habilis on is neoteny , or the “holding on” to features that are typical of newborn apes (Gould, 1977). A long period of learning is emblematic of the human species. What Do We Know About the Early Hominid Brain? Under rare circumstances a cast of the brain, showing features of its exterior surface, can survive. Endocasts , natural models of ancient brains, can show us what the exterior surface of an ancient brain looked like. Endocasts of Australopithecus africanus show that the exterior surfaces are indistinguishable from the brains of modern apes. Artificial endocasts of a Homo habilis specimen shows a far more humanlike, asymmetrical morphology. Brocca’s area.
Homo erectus migrations (2mya-0.8mya)
Dmanisi (1.7 mya) Atapuerca 780, Ubediya (1.5 mya) Sangiran (1.8 mya) Longgupo (1.9mya)
Expansion into Europe is later
Israel has the earliest firmly dated Acheulian assemblage outside Africa at 1.4-1mya Earliest European evidence from Gran Dolina, a cave at Atapuerca, Spain dated to 800,000 ka. Is attributed to Homo antecessor. This may be an offshoot of H. ergaster that disappeared after failed attempt to colonize southern Europe. No Acheulian at this age Then there is a gap until after 500,000-400,000 when several finds from Africa and Europe are grouped as Homo heildelburgensis. This is when Acheulian artifacts probably introduced to Europe. In Europe this may be the last common ancestor to both Neanderthals and modern humans.
Choppers Flakes Cores Homo habilis Australopithecus Garhi Oldowan Early Acheulian Handaxe Cleavers Cores Flakes Choppers Hard & soft hammers Homo erectus Late Acheulian
Issues and Debates
The “Art” of Making Tools
A high level of consistency in
handaxe form can be found
within sites, as if the makers
were adhering to a particular
standard.
That such extra care was taken in their production implies that their makers were interested in more than simple utility. Some have argued that evidence of bilateral symmetry in later hand- axes is related to cognitive development. Cf. Piaget’s developmental stages in children. Late Acheulian hand axe (Kalambo Falls)
African Acheulian complex
Early Acheulian Later Acheulian: Levallois, Sangoan, Fauresmith Sangoan Fauresmith
Hominids Conquer the World
China Stone artifacts (crude core tools and flakes) associated with Homo erectus were found in the Nihewan Basin of northern China show that they are approximately 1.36 million years old (Zhu et al. 2001). Europe The oldest unequivocal hominid remains found in western Europe were recovered at the site called Gran Dolina in the Atapuerca Mountains in Spain (Carbonell et al. 1995). Environmental stress, cannibalism, local extinction? It is reasonable to say that African hominids first entered Europe by at least 800,000 years ago.
Atapuerca, Spain
Gran Dolina Homo antecessor ca. 800 ka Gran Dolina has yielded the remains of at least 6 individuals dated from before 780,000 years ago. There is debate whether these represent a new species, or fall within the range of variation of other H. erectus specimens. Evidence for cannibalism is evident on 25% of bones with cut marks. This could be a sign of nutritional stress. Perhaps this unsuccessful adaptation represents a migration into Europe that failed?
Later Acheulian
Soft hammer Decrease in size Increase in symmetry Evidence for structures Seasonal transhumance “Ends” about 250,000 BP with new levallois technique added Regional variants of evolved Homo erectus
The Age of Ice
The earth became a significantly colder place, particularly after about 900,000 years ago, with northern latitudes and higher elevations becoming covered by expanding ice fields called glaciers (Shackelton and Opdyke 1973, 1976). The older period of time is called the Pleistocene epoch. The Pleistocene was an epoch of fluctuating climate, with periods called glacials much colder than the present. Within the glacials were colder and warmer periods, with attendant glacial advances ( stadials ) and retreats ( interstadials ). Between the glacials were relatively long interglacial periods, during which the temperature often approached, sometimes equaled, and rarely may even have exceeded the modern level. The worldwide sequence of glacial advances and retreats can be studied indirectly, via the ratio of two isotopes of oxygen ( 16 O: 18 O). The Shackleton and Opdyke curve (1973, 1976) covers the last 780, years. It exhibits 10 periods of drops in 16 O and, therefore, significantly colder temperatures and greater ice cover on the earth’s surface. Adaptive flexibility seems to have been a hallmark of the Homo erectus species.
When Did Homo Erectus Become Extinct?
Only the Homo erectus
population in Africa
( ergaster ) is directly
ancestral to us.
That line evolved into another hominid that looked and behaved more like modern humans. Ngandong, Java: fossils identified as erectus have been dated as late as 27,000-53,000 BP???
Stability or Change?
Homo erectus is one of the longest-lived of the hominid species. About 400,000 years ago a steep increase in brain size over a short interval is seen. Those changes produced and defined the first Homo sapiens.
The Multiregional Model
Proposed by Milford Wolpoff (Univ. of Michigan) The basic tenets of the theory are as follows:
- erectus evolves in Africa and is the first hominid to migrate out of Africa
- The species spreads through the Middle East and into Asia
- Once dispersed H. erectus evolves independently into H. sapiens neanderthalensis The chief implications of Multiregional model are:
- There is only 1 migration out of Africa
- All modern races of humans have evolved in situ and are directly or indirectly decended from H. erectus What evidence supports the Multiregional model? It is possible to detect the regional racial traits of modern humans in archaic hominids living in the same region Key problems with the Multiregional Model
- Not all researchers agree with the racial trait observations
- The problem of 'Parallel Evolution'
- There is not enough genetic variation in modern populations
