|PREHISTORIC LIFE HOME||PREHISTORIC LIFE TABLE OF CONTENTS||OBL HOME||OBL REFERENCES|
DATES: to 1.6 million years ago
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).
|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
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)
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 (
The assemblages of tools found with Homo erectus are more sophisticated than
earlier tools and 2 sites are associated with fire. In
erectus is considered to be the first hominid to travel out of
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
A fossil of a three foot tall hominid was found in Indonesian cave dating from a bout 18,000 years ago.
ARCHAIC Homo sapiens/ Homo heidelbergensis
DATES: 500 thousand years ago to 200 thousand years ago
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).
|THE PIT OF BONES: In
DATES: 230 to 30 thousand years ago
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 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
| 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
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.
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
--Regional Continuity Model:
Although modern humans did leave
Modern humans arrived in
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).