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HOMINIDS 3

Homo habilis

DATES: 2.5 to 1.6 million years ago

SITES: Olduvai, Tanzania; Koobi Fora, Kenya; Omo, Kenya; Sterkfontein, South Africa; Uraha,; Longuppo, China? (Culotta, 1995; Larick, 1996; Wanpo, 1996)

HOMINID SKULLs habilis
habilis hominid series
hominid series

CHARACTERISTICS:

     Homo habilis differs from Australopithecus at the base of the skull.  The foramen magnum (the opening for the spinal chord) is closer to the middle of the skull and the skull base is reduced in length but increased in width.  The face decreased in width and the nasal opening was more sharply defined.  The postcanine teeth were smaller than in Australopithecus.

     Its cranial capacity was 500 to 800 cc. and values increase from the earliest specimens to latest ones.  This range overlaps with Australopithecus at the low end and Homo erectus at the high end. It can be debated (indeed, there has been a debate several decades long) on whether early H. habilis should be classified as Australopithecus and late H. habilis should be called Homo erectus.  H. habilis stood approximately 5 foot tall and weighed 100 pounds with females being smaller than males (Leakey, 1973b; Wood, 1987; Leakey, 1971b; Hughes, 1977; Johansen, 1987; Bilsburough, 1988; Tobias, 1972).  Early Homo populations coexisted with australopithecines (Johanson, 1976).

     In one brain endocast, there is a bulge corresponding to Broca’s area (an important speech center) in modern human brains.  Two aspects of wrist bones (the scaphoid tubercle and the articular surface of the trapezium) were chimp-like.  The thumb was similar to humans in the carpo-metacarpal joint and the flattened metacarpal surface.  The foot was less flexible than in chimps and its degree of possible abduction was limited.  Some characteristics of the lower leg were primitive and others were advanced, not found in any ape (Susman, 1982; Skelton, 1986).  

habilis habilis
rudolfensis
     Homo habilis is translated as “handy man” referring to the simple stone tools found at many sites (Toth, 1985; Leakey, 1970).  Some feel that the variation in skulls is too great to accommodate in one species and classify some Homo habilis skulls as Homo rudolfensis (Wood, 1992; Wood, 1999)
     Hominids seemingly intermediate between Homo habilis and Homo erectus traveled outside Africa 1.6 million years ago.  The hominids which first arrived in central Asia possessed smaller brains, some only half the size of modern humans and smaller than usual for Homo erectus.  They were small-bodied, similar in size to Homo habilis (Wong, 2003a). 
Homo erectus

DATES: 1.8 million years ago to as late as10 to 27 thousand years ago (have been dated with K/Ar, Ar/Ar, U series, ESR, and faunal dating methods)

SITES: Kenya, Tanzania, Algeria, Morocco, Georgia, the Middle East, China, Indonesia, and Java

CHARACTERISTICS:

      The cranial capacities range from 750 to 1225 cc; early forms average 900 cc; later forms average 1100 cc.  The depth and robusticity of the zygomatic bone differs from modern humans.  H. erectus is similar to H. habilis in its protruding jaws, large molars, lack of a prominent chin, thick brow, and the long, low skull.  H. erectus had human limb proportions and human body shape (it was the first hominid to have this). Its skeleton more robust than modern humans, suggesting considerable strength (Rightmire, 1981; Brown, 1985; Leakey, 1973; Walker, 1981; Day, 1971; Clark, 1976; Leakey, 1976; Wolpoff, 1984.  There was some sexual dimorphism in the skeleton and one specimen shows signs of hypervitaminosis A (Walker, 1982).

     The assemblages of tools found with Homo erectus are more sophisticated than earlier tools and 2 sites are associated with fire.  In Asia, Homo erectus coexisted with Gigantopithecus.  In Africa, Homo erectus coexisted with Australopithecus (Leakey, 1971, Gowlett, 1981; Wanpo, 1995; Leakey, 1976b; Jacob, 1978; Weiner, 1998; Tianyuan, 1992).

erectus skull erectus skull
erectus skulls erectus skull
erectus skull
erectus skulls
erectus skulls erectus skull

     Homo erectus is considered to be the first hominid to travel out of Africa (although a find from China and others in Central Asia may belong to H. habilis rather than H. erectus).  Homo erectus is known from Asia (Java, China, Pakistan, and Georgia) as of 1.7 million years ago and the Middle East as of 1.5 million years ago (Gabunia, 1995; Klein, 1973; Larick, 1996; Howells, 1980)    

     Homo erectus is known in Java as early as 1.8 million years ago and as late as 50,000 years ago.  The combination of very thick crania and evidence of healed skull fractures and head trauma have caused some to propose that male Homo erectus fought with each other using clubs (Boaz, 2004).  The last Homo erectus populations existed in Java between 27 and 53 thousand years ago dates which overlap with the existence of Homo sapiens sapiens in the region (Gibbons, 1996; Thorne, 1972; Swisher, 1996).  The earliest African forms of Homo erectus have smaller and more projecting noses.  Some researchers classify these specimens as Homo ergaster and feel that Homo ergaster or some pre-erectus population migrated from Africa before H. erectus proper evolved.  One find of Homo from 1 million years ago from Afar (near the Red Sea) is similar to H. ergaster but also has characteristics of Homo sapiens.  Some anthropologists feel some skeletal characteristics (the frontal keel, torus mandibularis, os epactale, and incisor shape) of Asian erectus populations indicate that there was interbreeding between these populations and later H. sapiens emigrants from Africa.  The transitional nature of the fossil material makes it difficult to assert which populations should be regarded as separate species. (Dean, 1995; Lewin, 1989; Wolpoff, 1984; Turner, 1989; Gibbons, 1998; Abatte, 1998). 

chimp and erectus australopithecine and erectus
erectus skull

 

A fossil of a three foot tall hominid was found in Indonesian cave dating from a bout 18,000 years ago.

Flores humans had a brain the size of a grapefruit, more similar in size to extinct hominids and modern apes than to ours.  Despite this small size, Flores humans apparently used both tools and fire (Associated Press, 2004).

flores

ARCHAIC Homo sapiens/ Homo heidelbergensis

DATES: 500 thousand years ago to 200 thousand years ago

CHARACTERISTICS:

     The earliest specimens classified as archaic Homo sapiens or Homo heidelbergensis  have features of both H. erectus and H. sapiens sapiens with robust skeletons and teeth.  Some specimens have brow ridges, receding foreheads, and receding chins.  Some specimens already display some neanderthal facial characteristics (morphology of the eye sockets, cheekbones, and nasal bones) suggesting that neanderthals may have diverged from other lineages quite early.  There is an advanced expansion of the cranial vault and the average cranial capacity was 1200 cc (Brauer, 1993; Howell, 1952; Trinkaus, 1997; Stringer, 1988; Stringer 1993; Arsuaga, 1997).

       One significant change that occurred between the archaic and modern humans was a shortening of the sphenoid bone in the braincase.  Externally, this change resulted in jaws, which did not protrude to the same degree.  Internally, the change could have had a much more profound effect: it would have affected the dimensions of the oropharynx and the variety of sounds that humans could have made in speech.  (Chimps and gorillas are capable of large vocabularies when using sign language and their use of signs suggests a degree of complex thought which they were previously thought to be incapable of.  Apes do not speak because they do not have the anatomy for it.  Thus changes in the vocal tract could have had a much larger impact on language than increases in brain size.) (Hublin, 1996; Rightmire, 1997; Rightmire, 1976; Holden, 1998).

pharynx
THE PIT OF BONES: In Spain, the largest collection of Middle Pleistocene bones (1,600 bones from 32-50 individuals) was found dating at 300,000 years ago.  Humans had been in Spain long before that: fossils of early Homo are known from 800,000 years ago and one site which has tools may be 1.2 million years old.  As sea level rose and fell in the Pleistocene, there were times when the water levels separating Morocco and Spain were only half the current level so this migration would not have been difficult.  Some feel that the primitive characteristics of these skeletons (such as a brow ridge and multiple roots for the premolars) warrant their classification as Homo antecessor, distinct from Homo heidelbergensis.   If H. antecessor is distinct from H. heidelbergensis, it cannot yet be concluded whether H. heidelbergensis evolved from H. antecessor or from African Homo, (which bear similarities to H. heidelbergensis) which arrived at central Europe through the Middle East (Balter, 2001; Carbonell; 1995; Bermudez, 1997; Bahn, 1996). 
antecessor heidelbergensis
homo
homo
homo

 

Homo neanderthalis

DATES: 230 to 30 thousand years ago

SITES: throughout Europe east to Israel and Uzbekistan

CHARACTERISTICS:

     Although some neanderthal characteristics are found in modern humans or earlier Homo species, the combination of these characteristics in neanderthals is unique.  These characteristics increased in frequency as later neanderthals evolved.  As a result, there are differences between the robust “classic” neanderthals of Western Europe and the populations of the Middle East.  

     Neanderthals had a long trunk, short legs, and a robust skeleton.  The size of muscle attachment sites imply considerable muscle power.  A diastema (gap) exists between the jaw and lower wisdom teeth.  The skull and face were long, the forehead low, there were protruding brow ridges, the rear of the braincase was round (not pentagonal as in modern humans), there was a large nasal cavity, the floor of the eye socket was flat or even receding laterally, there was a strong mandible lacking a chin, a protruding midface, the cheekbones were weak and oriented obliquely, the occipital bone bulges posteriorly (the occipital bun, a trait which very rarely can still occur in modern humans), and the occipital bone has a conspicuous depression known as the sura-iniac fossa.  Hand bones indicate that Neanderthals may not have been as dextrous as modern humans (Musgrave, 1971; Trinkhaus, 1982).  Although neanderthal faces seem abnormally long, they are actually similar to earlier specimens of Homo.  Modern human faces are much shorter, including the region of the pharynx which affects the ability to produce the sounds of human speech (Trinkhaus, 2003).

     Males averaged 5’6” in height but because of their robustness, they may have averaged 30% larger than modern humans.  The average brain capacity was 1450 cc (a little larger than that of moderns) and one young male specimen had a capacity of 1750 cc (Kappelman, 1997).  While some concluded that neanderthal nasal specializations make them unique among hominids, others have refuted this (Schwartz, 1996; Laitman, 1996; Franciscus, 1999)..  Some neanderthal hand characteristics are unique.  Neanderthal hip morphology suggests that they were more active as children.  Some analyze this as a potential culture difference between neanderthals and the modern humans that replaced them (how active/mobile the young members of a group were).

     Between 300 and 127 thousand years ago there were two periods of glacial advance separated by a cool interglacial period and many features of the Neanderthal body are adaptations to cold temperatures.  Neanderthals have provided the first evidence of burying the dead 100 thousand years ago and later burials include animal bones and flint.  One 47,600-year-old cave has an impressive 4-meter x 5-meter structure built of stalagtites and stalagmites. Neanderthals arrived in Israel after modern humans and the two groups coexisted (with apparently no exchange of technologies) for 60 thousand years (Bar-Yosef, 1993; Hovers, 1996).  Neanderthals used fire and used more tools and weapons than Homo erectus.  The types of tools used change very gradually and the style of neanderthal tools are referred to as Mousterian.  At some sites, human and ungulate bones are smashed to similar degrees, suggesting cannibalism (Defleur, 1999; Jelinek, 1982).

.  In Southern Spain, Neanderthals survive 5-10,000 years after modern Homo sapiens appear in the north of Spain but they don’t acquire any new technologies.  In other parts of Europe, Neanderthals do acquire new technologies just before their disappearance, possibly as a result of interaction with modern Homo sapiens (Balter, 1996;). 

neanderthal neanderthal
skeleton
neanderthal neanderthal
neanderthal
     The craniofacial differences between Neanderthals and modern Europeans are greater than those observed between the two species of chimpanzee and between all modern human populations.  This suggests that Neanderthals were a separate species (Harvati, 2003; Harvati, 2004).  Genetic evidence also supports this conclusion.  Mitochondrial DNA was successfully isolated from neanderthal bone and the sequence was unlike any living human.  Its variation from modern humans is roughly half of the difference between humans and chimps. A second lab repeated this with identical results. Analysis of Cro-Magnon DNA of about the same age identified a sequence which was well within the variations of modern humans.  The conclusion drawn from this genetic evidence is that neanderthals are not related to living humans. An analysis of a fossil modern human mitochondrial genome indicated that it also went extinct-- if this one human’s mitochondrial genes are absent today, it is possible that neanderthals interbred with modern humans and their mitochondrial lineages disappeared as well.  Although mitochondrial DNA from several Neanderthals has identified DNA sequences which predate the origin of the mitochondrial strains which are known in modern living humans, anatomically modern humans from about 60 thousand years ago possessed a DNA segment on their mitochondrial chromosomes which now exists in the nucleus of modern human populations. Some feel that neanderthals and modern humans did interbreed and that neanderthals helped to contribute to European lineages (Caramelli, 2003; Adcook, 2001; Ward, 1997; Kahn, 1997; Mellars, 1998).  There is one fossil find of a young human from Portugal which may have a mix of neanderthal and modern human characteristics (Zilhoao, 2000).
MODERN HUMANS
modern archaic

Modern humans became lighter and more gracile.  (Gibbons, 1997).  The sphenoid bone shortened, meaning that the face did not project quite as far.  The skull became higher and rounder in contrast to the low, long skulls of Homo erectus and Neanderthals (Lieberman, 1998).  How did modern humans evolve?  There are two different models.

 

--Replacement Model:

     In the replacement model, it is thought that somewhere between 1 million and 100,000 years ago, modern humans left Africa, migrated throughout the continents, and completely replaced all other hominids (such as Homo erectus, Homo neanderthalis) so that they alone were ancestral to all modern human groups.  Proponents of this model vary on the timing, often due to discipline; paleontologists favor older dates, geneticists favor younger dates.  One strong piece of evidence that is frequently observed is that the greatest genetic difference in human populations occur between African populations.  The evidence for some of the oldest branches of humanity exist in Africa suggest that humanity evolved in Africa (Zischler, 1995; Waddle, 1994; Vigilant, 1991; Wood, 1997). Advanced tools (referred to as Acheulan; they included items such as hand axes) first appear in Africa and are known outside Africa as of 500,000 years ago (Lewin, 1987).

 

--Regional Continuity Model:

     Although modern humans did leave Africa over 100,000 years ago, they interbred with the hominid populations which were already present on other continents (Homo erectus in Asia, Homo neanderthalis in Europe) to produce many of the regional differences in modern humans.  The discovery of apparently ancient DNA sequences in Asian and Australian populations which are not found anywhere else in the world supports the model of regional continuity (Harding, 1997; Holden 2001).  Some anthropologists conclude that a number of fossil finds of Homo erectus and Homo neanderthalis have physical traits which correspond to the modern humans from those regions from much later dates (Wolpoff, 1993; Thorne, 1992; Thorne, 1981) .

  

      Modern humans arrived in Australia by 40-60,000 years ago (there are sites in East Timor which are slightly younger at 35,000 years old).  The Clovis culture of big game hunters is known in the New World as of 12,000 years ago.  In recent years, there have been a number of pre-Clovis sites found in both North America (ranging from 12-19,000 years old) and even in Chile (12,500 years old).  The ancestry of the first Americans may be more complex than what was first thought—some skeletal traits of fossils and genetic analyses indicate that native Americans are more similar to Europeans than Asians (Marshall, 2001; Pena, 1999; Gibbons, 2001; Holden, 1996; Morell, 1998).

      Molecular analyses point to three groups of aboriginal Americans: Amer-Ind, Na-Dene, and Eskimo.  The Na-Dene and Eskimo might not represent separate migrations but rather early offshoots of the Amer-Ind group which were isolated in northern regions by changing climates (Bonatto, 1997).