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Anatomically modern humans evolved from archaic
humans (500,000 years ago) in the Middle Paleolithic, about 200,000 years ago.[3]
The emergence of anatomically modern human marks the dawn of the subspecies
Homo sapiens sapiens,[4]
i.e. the subspecies of Homo sapiens that includes all modern humans.
“archaic humans and modern humans”
Contents
š›œš›œš›œš›œš›œš›œ
Timeline By 1.9 million years ago, some of
the early transitional humans had evolved into a new, fully human species in
Africa.
. This territorial expansion most likely began around
1.8-1.7 million years ago, coinciding with progressively cooler global
temperatures. Surprisingly, however, Homo erectus remained little
changed anatomically until about 800,000 years ago. After that
time, there apparently were evolutionary developments in features of the
head.
By half a million years ago, some Homo erectus were
able to move into the seasonally cold temperate zones of Asia and Europe.
This migration was made possible by greater intelligence and new cultural
technologies, probably including better hunting skills and the ability to
create fire.
. Homo erectus was a very successful
human species, lasting at least 1.5 million years, That evolutionary
transition was well under way by 400,000 years ago but was not
complete until 200,000-100,000 years ago and possibly even later
in some regions.
That evolutionary transition was well under way by
400,000 years ago but was not complete until 200,000-100,000 years
ago and possibly even later in some regions.
Ergaster & Erectus
\
By 1.9 million years ago, some of the early transitional humans had evolved into a new, fully human species in Africa. Most paleoanthropologists refer to them as Homo erectus
(literally
"upright human"). However, a few researchers split
them into two species--Homo ergaster (literally
"working human") and Homo erectus. The ergaster fossils
were presumably somewhat earlier and have been found for the most
part in Africa. The erectus discoveries have been found
widespread in Africa, Asia, and Europe. In this tutorial, ergaster and erectus will
be considered one species--Homo erectus.
By 1.9 million years ago, some of the early transitional humans had evolved into a new, fully human species in Africa. Most paleoanthropologists refer to them as Homo erectus
(literally
"upright human"). However, a few researchers split
them into two species--Homo ergaster (literally
"working human") and Homo erectus. The ergaster fossils
were presumably somewhat earlier and have been found for the most
part in Africa. The erectus discoveries have been found
widespread in Africa, Asia, and Europe. In this tutorial, ergaster and erectus will
be considered one species--Homo erectus.
 |
|
 |
|
Homo erectus from Southeast Asia
|
Homo ergaster from East Africa
|
|
Homo erectus were very successful
in creating cultural technologies that allowed them to adapt to new
environmental opportunities. They were true pioneers in
developing human culture and in expanding their geographic range beyond Africa
to populate tropical and subtropical zones elsewhere in the Old World.
This territorial expansion most likely began around 1.8-1.7 million years ago,
coinciding with progressively cooler global temperatures.
Surprisingly, however, Homo erectus remained little changed
anatomically until about 800,000 years ago. After that time,
there apparently were evolutionary developments in features of the head
that would become characteristic of modern humans. By half a
million years ago, some Homo erectus were able to move into
the seasonally cold temperate zones of Asia and Europe. This migration
was made possible by greater intelligence and new cultural technologies,
probably including better hunting skills and the ability to create fire.
Evolutionary Relationships
The earliest Homo erectus were
contemporaries of the late Homo habilis in East Africa for
several hundred thousand years. This suggests that the immediate ancestor
of Homo erectus was an early Homo habilis or possibly another
yet to be discovered species of early humans. Homo erectus was
a very successful human species, lasting at least 1.5 million years, though
their numbers apparently remained relatively low. Some of them eventually
evolved into our species, Homo sapiens .
That evolutionary transition was well under way by 400,000 years ago
but was not complete until 200,000-100,000 years ago
and possibly even later in some regions.
.
That evolutionary transition was well under way by 400,000 years ago
but was not complete until 200,000-100,000 years ago
and possibly even later in some regions.
History of DiscoveryPithecanthropus erectus
 Eugene
Dubois(1858-1940) |
In the late 19th century, our knowledge of human fossil ancestors
did not go back beyond that of the Neanderthals in Europe, less than
100,000 years ago, and little was known about them. There was no inkling
of our much earlier ancestors in Africa. A few scientists speculated that
the most ancient humans would be found somewhere in tropical regions
of East Asia. One of the people who held this view was a Dutch
anatomist and medical doctor named Eugene
Dubois .
Late in 1887, he went to the Dutch East Indies (now Indonesia) as a military
doctor. This job allowed him enough spare time to pursue
his passion, the search for early human fossils. He first explored
the big island of Sumatra. Excavating in several caves, he found a
hominid jaw fragment in 1890. However, this was not convincing evidence
of early human ancestry. He then moved on to Java. During
excavations in the eastern part of that island in 1891-1892, he recovered
a Homo erectus brain case and femur (upper
leg bone). Since he had discovered an unknown species, he took the
liberty of naming it in an 1894 publication. He called it Pithecanthropus erectus (literally
"ape man who stands erect"). He returned to the
Netherlands with his fossils in 1895 and proclaimed them to be from our
earliest ancestor. Unfortunately for Dubois, most of the leading
paleontologists of his day were not convinced.
.
Late in 1887, he went to the Dutch East Indies (now Indonesia) as a military
doctor. This job allowed him enough spare time to pursue
his passion, the search for early human fossils. He first explored
the big island of Sumatra. Excavating in several caves, he found a
hominid jaw fragment in 1890. However, this was not convincing evidence
of early human ancestry. He then moved on to Java. During
excavations in the eastern part of that island in 1891-1892, he recovered
a Homo erectus brain case and femur (upper
leg bone). Since he had discovered an unknown species, he took the
liberty of naming it in an 1894 publication. He called it Pithecanthropus erectus (literally
"ape man who stands erect"). He returned to the
Netherlands with his fossils in 1895 and proclaimed them to be from our
earliest ancestor. Unfortunately for Dubois, most of the leading
paleontologists of his day were not convinced.
“Java Man"
Dubois' claims for his Java Homo erectus finds
were not widely accepted until the 1930's, when the German/Dutch paleontologist
Gustav von Koenigswald made similar discoveries in the Dutch East Indies.
By that time, there had also been even more convincing discoveries of Homo
erectus in China. Dubois, now in his 70's, stubbornly
refused to accept any of these fossils as being from the same species as his
"Java Man" specimens. He died at the outset of World War II,
apparently as a rather lonely maverick scientist frustrated by the inability to
convince many people that his conclusions had been correct.
Radiometric Dating
Dating the Java Homo erectus fossils has
been difficult. In the past, it was generally accepted that most of these
bones are 700,000-200,000 years old, based roughly on what
was the presumed date for the geological strata in which they were
found. In 1994, however, radiometric dating of sand particles attached to
two of the fossils indicated that they were actually 1.8 and 1.6 million years
old.
These dates indicate that some Homo erectus left Africa soon after they evolved from early transitional humans.
 |
|
|
Davidson
Black
(1884-1934) |
In 1911, a revolution in China overthrew the last emperor of
the Manchu Dynasty and set up a Western-style republic under
the leadership of the American-educated Dr. Sun Yat-Sen. In
imitation of western nations, the Geological Survey of China was established in
1917 with a Swedish geologist named J. Gunnar Anderson as its advisor. Among the many tasks
of the Survey was the search for the source of "dragon
bones." This is a Chinese generic term for the fossil bones
that end up in apothecary shops as medicines. They are still popularly
used in a ground up form for healing wounds and fractures and treating
cramps and dizziness. Some older men in China use
them as sexual stimulants, though they are being replaced by modern drugs
such as Cialis, Viagra, and Levitra.
In 1921, Gunnar Anderson discovered that one of the
important sources of "dragon bones" in North China was an abandoned
limestone quarry near the village of
Zhoukoudian Zho ku den
Zhoukoudian 
.
.
This was only a day's drive over rough dirt roads from
Beijing. In 1927, a fossil was found in an ancient cave at
the base of the quarry that turned out to be a Homo erectus molar
tooth.
It was examined by Davidson
Black
A Canadian anatomy professor at Peking Union Medical
College. He identified the tooth as being from an earlier species of
human which he named Sinanthropus
pekinensis (literally
"Chinese man from Peking", or Beijing as it is now
called). This discovery sparked 10 years of intense
excavations at Zhoukoudian by Anderson, Black, and others (especially
Pei Wenshong after 1929
and Franz Weidenreich in
the mid-
(literally
"Chinese man from Peking", or Beijing as it is now
called). This discovery sparked 10 years of intense
excavations at Zhoukoudian by Anderson, Black, and others (especially
Pei Wenshong after 1929
and Franz Weidenreich in
the mid-|
"Peking Man" skull
 |
1930's). The bones of 50 individual Homo
erectus were eventually found there.
The Homo erectus skeletal evidence
at the "Peking Man" site of Zhoukoudian is especially important
because it is from a population of men, women, and children rather than just a
single individual. There was considerable sexual dimorphism and
individual variability. The human remains were associated with large
quantities of animal bones that apparently were mostly food refuse, though many
of them had been chewed by large carnivores and may have ended up in the cave
complex as a result of their activities.
A few of the bones had been burned in a way that suggests cooking. 780,000 years ago
In addition, more
than 100,000 stone, bone, antler, and horn tools were excavated. The cave
was intermittently occupied by late Homo erectus for around
300,000 years, beginning around 780,000 years ago.
With the exception of two teeth, all of the Homo erectus bones
from Zhoukoudian were lost in the chaos of late 1941 when the Japanese Army
invaded Beijing and other urban centers in eastern China. There have
been a number of intriguing guesses about what happened to the bones. The
last time they were accounted for was when they were turned over to a U.S.
Marine detachment, placed in wooden
foot-lockers, and possibly taken 140 miles from Beijing
to the American Camp Holcomb. They were to be
transported by ship to the U.S. for safety on an American freighter named
the President Harrison. However, after the U.S. entered the war on
December 7, 1941, Japanese forces quickly seized Camp Holcomb. At that
point in time, the Zhoukoudian fossils disappeared and have never
reappeared. In 1949, the Peoples Republic of China established a $100,000
reward for their return. Unfortunately, it has not been claimed.
The only surviving bones were the two teeth that had not been turned over to
the Marines in 1941.
The loss to science of the Zhoukoudian bones was not as great
as it may initially seem. Earlier, they had been measured, photographed,
and excellent casts of them had been successfully sent to the U.S.by Franz
Weidenreich where they were kept safe during World War II. In addition,
other Homo erectus skeletal material has been excavated in China
since the mid 1960's. Most notably are the finds that were recovered
from Lantian County, Shensi Province. These fossils from
several Chinese sites date to at least 800,000 years ago.
|
"Turkana Boy"
 |
1960 "Turkana Boy."
In 1960, Louis
and Mary Leakey found a 1.25 million year old Homo erectus partial
cranium at Olduvai Gorge.
Subsequently, more Homo erectus fossils were discovered there
and at other sites in East, South, and Northwest Africa. The oldest
known Homo erectus date to nearly 2 million years
ago in East Africa. This strongly suggests that Homo erectus originated
there. In 1984, Richard
Leakey's team working at Nariokotome on
the western side of Lake Turkana found a nearly complete Homo erectus skeleton
of an 8-12 year old boy dating to 1.6 million years ago. It is
usually referred to as the "Turkana
Boy." The significance of this discovery will be discussed
below.
Three surprisingly early Homo erectus skulls
were found during the 1990's on the fringes of Eastern Europe at Dmanisi in the Republic of
Georgia. They date to 1.75 million years ago and look very much like
the earliest Homo erectus from Africa--i.e., those that have
been classified by some researchers asHomo ergaster. This
discovery lends credence to the 1.8 and 1.6 million year old dates for Homo
erectus from Java and to an early rather than late Homo
erectus expansion out of Africa.
Homo erectus precededHomo heidelbergensis
the genus of Neandertals
Homo erectus-like bones were also discovered
during the 1990's from several other sites in Western Europe and Africa that
date 800,000-400,000 years ago. It has been difficult to assign these
fossils to specific species due to the fact that they have characteristics of
both Homo erectus and more recent human
species. Some paleoanthropologists consider them to be late
transitional Homo erectus. Others now suggest that
they are Homo heidelbergensis,
a subsequent species that descended from Homo erectus and preceded Neandertals
and other archaic humans. That is the approach taken in this
tutorial series. This particular difference of species
assignment is not particularly important and it does not detract from our
growing understanding of the broad evolutionary trends. It is a result of
our evolving conceptualization of the past as more data become available.
It also partly reflects the fact that the picture of human evolution looks
somewhat dissimilar in different regions of the World. It is
now becoming clear that our evolution was not as straight forward as
it once was commonly thought. Humans in some areas lagged behind.
This was particularly true on some islands of Indonesia. At Ngandong on Java, for
instance, Homo erectus may have survived to 53,000 years ago
or even somewhat later.
Important Homo erectus Sites |
|
|
Location
|
Date of Fossil
(years ago) |
|
Africa:
|
|
|
East
Turkana
|
1,900,000-1,600,000
|
|
WestTurkana
|
1,500,000
|
|
OlduvaiGorge
|
1,300,000-700,000
|
|
Bouri
|
1,000,000
|
|
Swartkrans
|
1,800,000-1,500,000
|
|
Ternifine
|
700,000-500,000
|
|
Sale
|
400,000
|
|
Israel:
|
|
|
Ubeidiya
|
1,600,000-1,400,000
|
|
Dmanisi
|
600-650
|
|
Java:
|
|
|
Modjokerto
|
1,800,000
|
|
Sangiran
|
1,800,000-1,600,000
|
|
Trinil
|
900,000 ?
|
|
Ngandong
|
546,000-143,000 ?
|
|
China:
|
|
|
Yuanmou
|
1,700,000 ?
|
|
Lantian
|
800,000
|
|
Zhoukoudian
|
770,000-400,000
|
|
Hexian
|
400,000
|
 Note: Several human fossils dating
800,000-400,000 years ago are controversial. They are classified
as Homo erectus by some researchers and Homo
heidelbergensis (a later human species) by others. They will
be presented in the next tutorial of this series.Note: It is likely that Homo erectus reached Java and other Indonesian islands during glacial periods when sea levels were low enough to create a land connection with the Southeast Asian mainland. |
Homo erectus Anatomy
 |
|
|
Homo erectus
|
|
Below the neck, Homo
erectus were anatomically much like modern humans.
Their arm and leg bones were essentially the same as modern people in
shape and relative proportions. This strongly supports the view that they
were equal to us in their ability to walk and run bipedally. However,
their leg bones were apparently denser than ours. This may be partly a
result of developmental adjustment differences. Unlike us, these early humans
did not spend much of their lives sitting behind desks or on a sofa
watching TV. They were probably much more active throughout the
day seeking food.
Their legs would have
made Homo erectus efficient long distance runners like modern
humans. It has been suggested that this capability would have allowed
them to run down small and even medium size game animals on the tropical
savannas of East Africa. If this was the case, it is also likely
that they were largely hairless by this time. Bodies with little hair are
more efficient at remaining cool via the evaporation of sweat during times of
heavy exertion. Four legged mammals primarily cool their bodies by
panting. Because they are unable to pant while galloping, they readily
overheat in hot weather. As a consequence, they cannot run long distances
without collapsing from heat exhaustion. This gives human hunters a
decisive advantage when chasing them.
It also has been suggested
that the pelvis in early Homo erectus may have
been a bit narrower than in modern humans, which would require the infant brain
to be smaller at birth and to then undergo considerable growth in
childhood. However, we must be careful to not make too much of these
differences because the number of existing specimens is low and there were
minor regional variations as well. This becomes apparent especially when
comparing Homo erectus from East Asia and Africa.
in early Homo erectus may have
been a bit narrower than in modern humans, which would require the infant brain
to be smaller at birth and to then undergo considerable growth in
childhood. However, we must be careful to not make too much of these
differences because the number of existing specimens is low and there were
minor regional variations as well. This becomes apparent especially when
comparing Homo erectus from East Asia and Africa.
With the evolution of Homo
erectus, there was a significant increase in body size compared to earlier
hominids. Past estimates of Homo erectus stature
frequently were in the 5-5½ feet (152-168 cm)range for adult males and
around 88-150 pounds (40-68 kg). The discovery of the
"Turkana Boy" in 1984 brought this into question. This is not
only the most complete specimen of this species so fardiscovered, but it is one
of the earliest. The boy was only 8-12 years old when he died but
already 5 feet 3 inches (160 cm) tall. If he had lived to
adulthood, he very likely would have grown to 6 feet (180 cm), assuming
that Homo erectus growth patterns were similar to ours.
As the number of nearly complete Homo erectus skeletons
increases in the future, a clearer understanding of the range of their stature
and body shape will likely emerge.
Homo erectus heads were strikingly different from ours in
shape. They had relatively strong muscles on the back of their
necks. Their foreheads were shallow, sloping back from very
prominent bonybrow ridges (i.e., supraorbital tori ). Compared to modern humans, the Homo
erectus brain case was more elongated from front to back and less
spherical. As a consequence, the frontal and temporallobes
of their brains were narrower, suggesting that they would have had somewhat
lower mental ability.
). Compared to modern humans, the Homo
erectus brain case was more elongated from front to back and less
spherical. As a consequence, the frontal and temporallobes
of their brains were narrower, suggesting that they would have had somewhat
lower mental ability.
 |
|
|
Homo
erectus
(from Java) |
Homo sapiens
(modern human) |
|
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 |
||||
|
shovel-shaped
incisors |
||||
The adult Homo
erectus brain size ranged from around 750 to 1250 cm3,
averaging about 930 cm3. This was only around 69% the
size of modern human brains on average but 50% larger than Homo habilis.
The upper end of the Homo erectus brain size range overlapped
that of modern people. However, the larger brained Homo
erectus mostly were relatively late in time and are considered by
some paleoanthropologists to be a more recent human species (Homo
heidelbergensis or early archaic humans).
Homo erectus teeth were generally intermediate between modern
humans and the australopithecines in shape and size. The teeth of
later Homo erectus were generally smaller than the earlier
members of this species. This was particularly true of molars. This
evolutionary trend probably reflects a progressive change in diet to softer
foods, including more meat and eventually cooked food. The incisor teeth
of Homo erectus generally have a "scooped out"
appearance on the tongue side. These "shovel-shaped" incisors
are also found among many Asians and Native Americans today.
It is likely that increased
meat consumption had a significant impact on the biological success of early
humans. It provided the calories in a more easily digestible, concentrated
form needed to maintain larger brains. The additional useable calories
also made it possible for women to have shorter time periods between
pregnancies and to subsequently give birth to more children during their
reproductive years. As a result, there was an acceleration of human
population growth which was very likely an important contributing factor in the
spread of people out of Africa and into Asia and Europe for the first time.
|
Food For Thought: Meat-Based Diet Made Us Smarter--audio recording of an NPR interview with anthropologists
Leslie Aiello and Richard Wrangham concerning the relationship between
switching from a predominantly vegetable diet to one that contains large
amounts of meat and the evolution of large human brains. This
link takes you to an external website. To return here, you
must click the "back" button on your browser program (length = 7 mins, 46 secs) |
Homo floresiensis
In 2003, a team of Australian
paleoanthropologists led by Peter Brown discovered a skeleton from what
may be a dwarf Homo erectus or related species that lived
until 18,000 years ago on Flores Island, Indonesia. This 30 year old
adult female was only about 3 feet 6 inches tall (106 cm), 66 pounds (30
kg), and had a brain size of 380 cm3 (like those of
australopithecines, barely 1/3 as big as modern human brains). This find
implies that a population of exceptionally small Homo erectus or Homo
erectus-derived humans survived on this relatively isolated island east of
Java until far later than previously believed. Brown refers to this new
discovery as Homo floresiensis . The bones of 8 additional individuals of this
cave dwelling population were subsequently found on Flores Island.
. The bones of 8 additional individuals of this
cave dwelling population were subsequently found on Flores Island.
At present, there is no clear
consensus among paleoanthropologists as to the place of floresiensis in
human evolution. Peter Brown and his colleague, Michael Norwood,
suggest that floresiensis may have been a descendent of normal
size Homo erectus who arrived in this area of Indonesia about
800,000 years ago or even earlier and that they became small as a result of a
well known biological phenomenon referred to as "island
dwarfing". They also believe that floresiensis may
have survived on the island until a devastating volcano wiped them out, along
with dwarf elephants, around 12,000 years ago. Critics suggest that the
Flores Island dwarfs were, in fact, modern people who suffered from
microcephaly, a pituitary gland disorder known as Laron syndrome, or
hypothyroidism due to a lack of iodine in their diet.
The short video clip and the
narrated slide show linked below will help you get a better understanding of
this intriguing discovery.
 Hobbits on Flores, Indonesia--A tiny hominin found on the island of
Flores, Indonesiahas shaken up the world of paleoanthropology. Human Origins
scientist Matt Tocheri explains why.This link takes you to an external
website. To return here, you must click the
"back"button onyour browser program. (length = 4 mins 19 secs) |
|
The Fellowship of the Hobbit: Elizabeth Culotta
Interviews "Hobbit" Scientists-- audio recording and slide show of the 2007 field season, excerpt from the Science Multimedia Center, AAAS This link takes you to an external website. To return here, you must click the "back"button on your browser program (length = 7 mins 19 secs) |
Argon/argon radiometric
method dates homo floresiensisto 1.08-1.02 million years ago.
Just how long humans have
been on Flores Island is not clear. The volcanic ash layer above
several simple flake artifacts found there has been dated with the argon/argon
radiometric method to 1.08-1.02 million years ago. Presumably, this sets
a minimum age for Homo floresiensis or their
predecessors on the island.
NEWS of Homo habilis
NEWS: In the
August 9, 2007 issue of Nature, Fred Spoor et.al., reported that a
1.44 million year old Homo habilis fossil was found at the Koobi Fora Formation
east of Lake Turkana in Kenya. If this date proves to be reliable, it
will confirm that Homo habilis lived until several hundred thousand years later
than previously assumed. It also provides additional support for the
assumption that Homo habilis was a contemporary of early Homo erectus rather
than only a predecessor.
NEWS: In the
February 27, 2009 issue of Science, Matthew Bennett et.al.,
reported the discovery of 2 sets of 1.51-1.53 million year old Homo erectus
footprints near Lleret, Kenya. These prints are said to be essentially
like those of modern humans.
Radiometric method based on the decay of aluminum and beryllium isotopes
NEWS: In the
March 11, 2009 issue of Nature, Guanjun Shen et.al., reported that
a joint Chinese and American research team was able to date the lower
occupation levels at Zhoukoudian to 680,000-780,000 years ago using a new
radiometric method based on the decay of aluminum and beryllium isotopes (26Al
and 10Be) found in quartz grains. These dates place Homo
erectus at Zhoukoudian around 200,000 years earlier than previously
thought. It also establishes that they were present at the time of a mild
glacial period.
NEWS: In the
May 7, 2009 issue of Nature, W. L. Jungers et.al., reported that
the feet of Homo floresiensis were relatively long with stubby big toes and no
arches. This means that their feet had a combination of human and
early hominin traits and implies that their gait was not as efficient as that
of modern humans for long distance walking.
Copyright © 1999-2013 by Dennis O'Neil. All
rights reserved.
illustration credits
illustration credits
«««End of Homo erectus A Beautiful Article
›œœ›š››œœ›š››œœ›š›
Climate Change and Human Evolution
The evolutionary surge that
led to Homo habilis began during the transition between the Pliocene and
Pleistocene Epochs around 2.5 million years ago when climates were becoming
cooler and drier. All later species of Homo evolved during the
Pleistocene (2,600,000-11,700 years ago). This was generally a time of
more extreme world cooling and recurrent glaciations (ice ages). During the coldest periods,
global temperatures dropped by about 9º F. (5º C.) and long-lasting ice sheets
spread out from the poles and high mountains. Between the four or more major
glaciations of the Pleistocene, there were interglacial
warming periods with temperatures similar to now. Both the glacials and
the interglacials lasted tens of thousands of years. Very likely, we are
now in an interglacial that began 10,000-12,000 years ago.
Very likely, we are now in an interglacial that began
10,000-12,000 years ago.
Changing Climate Patterns of the Pleistocene Epoch
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Note on Ice Ages
  These time ranges are
approximations and do not reflect the fact that temperature changes between
glacials and interglacials usually occurred over thousands of years. (principal sources: P. Gibbard and T. Van Kolfschoten (2004) "The Pleistocene and Holocene Epochs", ch. 22, in F. M. Gradstein et.al., A Geologic Time Scale (2004), Cambridge University Press) ** The use of pre-Illinoan climate stage designations for North America is controversial because the terms have been used inconsistently to describe different climatic events. Many geologists prefer for now to lump the Yarmouth, Kansan, Aftonian, and Nebraskan together into a single pre-Illinoian stage. |
The continents of the northern hemisphere were more affected
by glaciations than the southern ones, which generally remained mostly tropical
and subtropical, though more humid during ice ages. The coldest regions
of the world became arctic deserts. However, the great hot deserts of
North Africa and Western North America today were mostly vast grasslands with
large permanent lakes and abundant large game animals during the Pleistocene
ice ages. Sea levels were up to 450 feet (137 m.) lower than today during
the coldest periods as a result of a substantial volume of the world's water
being locked on the continents in 1-2 mile (ca. 1.5-3 km.) thick glacial sheets
covering thousands of square miles. As a consequence, vast areas that are
now shallow sea and ocean bottoms were exposed for thousands of years.
Twice during the last ice age, lowered sea levels resulted in Siberia being
connected to Alaska by a 1200-1300 mile (1900-2100 km.) wide corridor. Asian
hunters used this route to migrate into the western hemisphere to become the
first Native Americans.
Human evolution was very likely affected
strongly by the dramatic climate swings of the Pleistocene. These changes
no doubt presented powerful new natural selection pressures. Many animal
species were driven to extinction by the advancing and retreating ice
ages. Humanity survived primarily by becoming more intelligent and
adaptable. This allowed us to develop new cultural technology to deal
with cold environments and changing food sources, especially during the last
1/4 million years. One of the greatest problems in the cold regions would
have been the relative scarcity of plant foods that humans could eat during the
winters. In response to this, our ancestors became more proficient at
hunting animals, especially large ones that provided more calories. This
required inventing more sophisticated hunting skills as well as better weapons
and butchering tools. These changes in subsistence pattern were essential for our survival.
Extent of major glaciers at the
height of the last ice age (20,000 b.p.)
(27% of the earth's land surfaces were covered by ice at that time)
(27% of the earth's land surfaces were covered by ice at that time)
During ice ages, those
species that were not driven to extinction by the cold commonly evolved larger,
more massive bodies as a means of producing and retaining more heat. This
was especially true of mammals in the northern hemisphere. This is to be
expected, given the predictions of Bergmann's rule.
Humans evolved larger bodies during the Pleistocene as well.
|
Likely effects of
extreme cold conditions on human evolution To return here, you must click the "back" button on your browser program. (length = 3 mins, 51 secs) |
Note on global; cooling events
Global cooling events that
result in ice ages have occurred a number of times during the earth's
history. Some of these cold periods have lasted for 10's of millions of
years. The ice ages of the Pleistocene were just the recent part of a
longer progressively cooling trend that began about 60 million years ago.
By 35-30 million years ago, it was finally cold enough for the most recent
polar ice sheets to form.
|
Major Long-term Cold
Periods Over the Last 1/2 Billion Years
(shown in blue) |
Research by
Eelco Rohling of the University of Southampton in England suggests that we are
now 2,000-2,500 years overdue for another ice age and that the reason it has
not arrived yet has been the impact of humans on the global climate.
Specifically, it is thought that deforestation, the burning of fossil fuels,
and other human activities have resulted in an atmospheric "greenhouse
effect" which is responsible for prolonging relatively warm interglacial
conditions
End of Changing Climate Patterns of the Pleistocene Epoch
Early Human Culture
Tool Making
Some chimpanzee communities are known to use stone and wood
as hammers to crack nuts and as crude ineffective weapons in hunting small
animals, including monkeys. However, they rarely shape their tools in a
systematic way to increase efficiency. The most sophisticated chimpanzee
tools are small, slender tree branches from which they strip off the
leaves. These twigs are then used as probes for some of their favorite
foods--termites and ants. More rarely, chimpanzees have been observed using
sticks as short thrusting spears to hunt gallagos in holes and crevices of
trees where they sleep during the day time. It is likely that the
australopithecines were at least this sophisticated in their simple tool use.
|
|
 |
|
|
|
|
The first unquestionable stone tools were evidently made and
used by early transitional humans and possibly Australopithecus garhi in
East Africa about 2.5 million years ago. While the earliest sites with
these tools are from the Gona River Region of Ethiopia, simple tools of this
kind were first discovered by Mary and Louis Leakey associated with Homo
habilis at Olduvai Gorge in Tanzania. Hence, they were named Oldowan tools
after that location. These early toolmakers were selective in choosing
particular rock materials for their artifacts. They usually chose hard
water-worn creek cobbles made out of volcanic rock.
tools
after that location. These early toolmakers were selective in choosing
particular rock materials for their artifacts. They usually chose hard
water-worn creek cobbles made out of volcanic rock.
There were two main categories of tools in the Oldowan
tradition. There were stone cobbles with several flakes knocked off usually
at one end by heavy glancing percussion blows from another rock used as a
hammer. This produced a jagged, chopping or cleaver-like implement that
fit easily in the hand. These core
tools most likely functioned as multipurpose hammering, chopping, and
digging implements. Efficient use of this percussion flaking technique requires a strong precision
grip. Humans are the only living primates that have this anatomical
trait. Probably the most important tools in the Oldowan tradition were
sharp-edged stone flakes produced in the process of making the core
tools. These simple flake tools
were used without further modification as knives. They would have been
essential for butchering large animals, because human teeth and fingers are
totally inadequate for cutting through thick skins and slicing off pieces of
meat. Evidence of their use in this manner can be seen in cut marks that
still are visible on bones. Some paleoanthropologists have suggested that
the core tools were, in fact, only sources for the flake tools and that the
cores had little other use.
|
A Handy
Bunch: Tools, Thumbs Helped Us Thrive--audio recording of an NPR
interview with anthropologists Erin Williams and Dennis Sandgathe concerning the relationship between stone tool making and the evolution of the human hand. This link takes you to an external website. To return here, you must click the "back" button on your browser program. (length = 7 mins, 46 secs) |
In addition to stone tools, Homo habilis probably
made simple implements out of wood and other highly perishable materials that
have not survived. In the 1940's, Raymond Dart suggested that
australopithecines and early humans also used the hard body parts of animals as
clubs, daggers, and other sorts of weapons. Dart proposed an entire tool
making tradition which he named osteodontokeratic
,
based on the presumed use of bones (osteo), teeth (donto), and horns
(keratic). This idea has been rejected by most paleoanthropologists today
since there is a lack of evidence for the systematic shaping or even use of
these materials for weapons or other types of tools at this early time.
In addition, it is unlikely that the earliest humans were aggressive
hunters. They most likely were primarily vegetarians who occasionally ate
meat that was mostly scavenged from the leftovers of kills abandoned by lions,
leopards, and other large predators. At times, they also may have hunted
monkeys and other small game much as chimpanzees do today.
,
based on the presumed use of bones (osteo), teeth (donto), and horns
(keratic). This idea has been rejected by most paleoanthropologists today
since there is a lack of evidence for the systematic shaping or even use of
these materials for weapons or other types of tools at this early time.
In addition, it is unlikely that the earliest humans were aggressive
hunters. They most likely were primarily vegetarians who occasionally ate
meat that was mostly scavenged from the leftovers of kills abandoned by lions,
leopards, and other large predators. At times, they also may have hunted
monkeys and other small game much as chimpanzees do today.
Homo habilis made and used stone tools in the Oldowan
tradition for nearly a million years but with gradual improvements over
time. The early Homo erectus also used what could be described as
advanced or evolved Oldowan tool making techniques. By 1.8 million years
ago, the skills of some Homo erectus had increased to the point that
they were making more sophisticated stone implements with sharper and
straighter edges. Their tool kits were sufficiently advanced by 1.5
million years ago to consider them to be a new tool making tradition now
referred to as Acheulian .
It was named after the Saint Acheul site in southwest France where these kinds
of tools had been discovered in the 19th century. However, the Acheulian
tool making tradition was first developed in East Africa. Perhaps, the
most important of the Acheulian tools were hand axes. They are rock cores or very large flakes that
have been systematically worked by percussion
flaking to an elongated oval shape with one pointed end and sharp edges on
the sides. Since they were shaped on both faces, they are also referred
to as biface tools.
In profile, hand axes usually had a relatively symmetrical teardrop or broad
leaf shape. Referring to these artifacts as hand axes may be misleading
since we do not know for sure whether they were primarily axes in a modern
sense or even if they were held in the hand. Based on tool edge wear
patterns and the brittle fracturing lithic materials that were used to make
them, it is likely that hand axes were multipurpose implements used for light
chopping of wood, digging up roots and bulbs, butchering animals, and cracking
nuts and small bones. In a sense, they were the Swiss Army knives of their
times. They were reusable portable tools intended to be carried from
place to place rather than made each time they were needed.
.
It was named after the Saint Acheul site in southwest France where these kinds
of tools had been discovered in the 19th century. However, the Acheulian
tool making tradition was first developed in East Africa. Perhaps, the
most important of the Acheulian tools were hand axes. They are rock cores or very large flakes that
have been systematically worked by percussion
flaking to an elongated oval shape with one pointed end and sharp edges on
the sides. Since they were shaped on both faces, they are also referred
to as biface tools.
In profile, hand axes usually had a relatively symmetrical teardrop or broad
leaf shape. Referring to these artifacts as hand axes may be misleading
since we do not know for sure whether they were primarily axes in a modern
sense or even if they were held in the hand. Based on tool edge wear
patterns and the brittle fracturing lithic materials that were used to make
them, it is likely that hand axes were multipurpose implements used for light
chopping of wood, digging up roots and bulbs, butchering animals, and cracking
nuts and small bones. In a sense, they were the Swiss Army knives of their
times. They were reusable portable tools intended to be carried from
place to place rather than made each time they were needed.
 |
|
Acheulian bifaces (hand axes)--the earliest known
bilaterally symmetrical tools
|
Some of the Acheulian tools were shaped by additional
percussion flaking to relatively standardized forms. For instance, the
surfaces of late Acheulian hand axes often had many relatively small flake
scars, suggesting that these tools were not completely made with heavy
hammerstones. Late Homo erectus or their immediate successors must
have begun using softer hammers for greater control in the final shaping
process. Pieces of hard wood, antler, or bone would have functioned well
for this purpose.
 |
 |
|
Percussion Flaking Techniques: hard hammer (left) and soft
hammer (right)
|
|
While hand axes are the most diagnostic of Acheulian tools,
they usually make up only a small percentage of the artifacts found at Homo
erectus sites. In fact, these early humans made a relatively wide
variety of stone tools that were used for processing various plant and animal
materials. Their tool kits included choppers, cleavers, and hammers as
well as flakes used as knives and scrapers. It is quite likely that Homo
erectus also made many implements out of more perishable materials such as
wood, bark, and even grass, which can be easily twisted together to make string
and rope.
The Acheulian tradition of tool making apparently began in
East and South Africa by 1.5 million years ago. It spread into Israel and
probably other parts of Southwest Asia by 1.4 million years ago. However, not
all early Homo erectus leaving Africa had Acheulian tools.
Apparently, some only had the older Oldowan tradition. Acheulian tool
making reached Europe by at least 500,000 years ago and possibly as early as
900,000 years ago. Until recently, the lack of hand axes at Zhoukoudian
and other East Asian Homo erectus sites suggested that the Acheulian
tradition did not reach that far. It was thought likely that the same
functions that hand axes performed in the west were being performed in the Far
East by other kinds of tools, perhaps made of bamboo. However, 24 sites
in southern China have now been found to contain Acheulian tools dating back about
800,000 years. There remains controversy as to whether they include true
hand axes.
Throughout most of the Homo erectus geographic range,
there is clear evidence of progressive improvement in tool making over
time. The late Homo erectus had more complex mental templates
guiding them in the manufacture of their artifacts. In addition,
the reliance on tools increased as the implements became more useful. By
half a million years ago, major Homo erectus habitation sites commonly
had tens of thousands of discarded stone tools.
New Subsistence Patterns
Anthropologists use the term subsistence pattern, or subsistence
base, to refer to sources of food and the way it is obtained. A
clear measure of success in human evolution has been the progressive
development of new food getting techniques and the inclusion of new food
sources. These measures have made it possible for humanity to increase in
numbers from a few thousand australopithecines in Africa three million years
ago to perhaps hundreds of thousands of Homo erectus by a half million
years ago. This trend of expanding and diversifying subsistence patterns
making it possible for population growth continues to the present. In
fact, it accelerated dramatically two centuries ago and is largely responsible
for our burgeoning world population of seven billion people today. Our
modern hybridization and genetic modification of food crops and farm animals is
just the latest human attempt to solve this recurring problem.
Based on the analysis of tooth wear patterns and food refuse
evidence, it is likely that australopithecines and early transitional humans
were primarily wild plant food collectors and occasional scavengers of meat and
eggs. By the time of Homo erectus, small game hunting and large
animal carcass scavenging were apparently becoming much more common. The
evidence of this change in subsistence pattern can be seen especially at late Homo
erectus sites such as Zhoukoudian. Literally tens of thousands of
fragmentary food refuse bones were found there. They came from pigs,
sheep, rhinoceros, buffalo, and especially deer. In addition, there were
large numbers of bones from small animals including birds, turtles, rabbits,
rodents, and fish as well as the shells of oysters, limpets, and mussels.
Some of these bones ended up in the cave at Zhoukoudian as a result of large
carnivorous animals rather than humans, but there is sufficient evidence to
suggest that by a half million years ago, some Homo erectus were
exploiting virtually every animal in their environment for food. They
undoubtedly were harvesting vast amounts of wild plant foods as well. It
would be a mistake to assume that Homo erectus had become an efficient
specialized big game hunter. That development did not occur until more
advanced forms of humans had evolved, several hundred thousand years
later.
Occupation of New Environmental Zones
Homo erectus was the first species in our line of
evolution to expand their range beyond tropical and subtropical
environments into temperate
climatic zones of the Old World where they encountered relatively cold
winters. This occurred by at least a half million years ago in Asia and
evidently a few hundred thousand years earlier in Southern Europe. It was
made possible mainly by the success of new inventions and new subsistence
strategies. The most important change may have been increased meat
consumption as a result of hunting and more successful scavenging. The
greatest difficulty living in temperate areas was probably not the cold weather
but obtaining something to eat during the winter when fresh plant foods are
scarce. It is in that season that meat would have been the most important
calorie source.
The ability to use fire for cooking and heating may also
have been significant in the successful colonization of colder regions.
However, the first convincing evidence of regular fire use for these purposes
does not come until 780,000-400,000 years ago, when Homo erectus were
evolving into Homo heidelbergensis .
The earliest suggestive evidence of fire being associated with humans was found
at two sites in Kenya dating to 1.5 million years ago. In both
cases, soil sediments appear to have been exposed to high temperatures.
However, it is not necessary to assume that early humans were
responsible. The burned soil could have resulted naturally from lightning
started wild fires that are common in the grasslands of East Africa even today.
Similar questionable evidence has been found in South Africa dating to
about 1,000,000 years ago. There is no convincing evidence of human
control of fire at this early time. A 790,000 year old site in
Israel has more credible evidence, though there does not seem to have been any
cooking or repeated fire creation. The first reasonably good evidence of
cooking is in the form of burned bones and fire altered stones at the Chinese
site of Zhoukoudian dating sometime between 780,000 and 400,000 years
ago. All of these sites in Africa and Asia with uncertain fire use
indications presumably would have been occupied by Homo erectus.
We have no evidence as to how Homo erectus might have
obtained fire or even if they had the ability to create it at will.
.
The earliest suggestive evidence of fire being associated with humans was found
at two sites in Kenya dating to 1.5 million years ago. In both
cases, soil sediments appear to have been exposed to high temperatures.
However, it is not necessary to assume that early humans were
responsible. The burned soil could have resulted naturally from lightning
started wild fires that are common in the grasslands of East Africa even today.
Similar questionable evidence has been found in South Africa dating to
about 1,000,000 years ago. There is no convincing evidence of human
control of fire at this early time. A 790,000 year old site in
Israel has more credible evidence, though there does not seem to have been any
cooking or repeated fire creation. The first reasonably good evidence of
cooking is in the form of burned bones and fire altered stones at the Chinese
site of Zhoukoudian dating sometime between 780,000 and 400,000 years
ago. All of these sites in Africa and Asia with uncertain fire use
indications presumably would have been occupied by Homo erectus.
We have no evidence as to how Homo erectus might have
obtained fire or even if they had the ability to create it at will.
Implications
The cultural developments of Homo erectus essentially
began a new phase of our evolution--one in which natural selection was altered
by cultural inventions. This has been referred to as biocultural evolution. Culture
can affect the direction of human evolution by creating non-biological
solutions to environmental challenges. This potentially reduces the need
to evolve genetic responses to the challenges. Normally, when animals
move into new environmental zones, natural selection, operating on random mutations,
causes evolution. In other words, the population's gene pool is altered
as a result of adapting to a new environment. When late Homo erectus
moved into temperate environments, nature should have selected for biological
adaptations that were more suited to cooler climates. Such things as
increased amounts of insulating body fat and insulating hair covering most of
the body would be expected. Homo erectus evidently achieved much
of the same adaptation by occupying caves, using fires, and becoming more
capable at obtaining meat. By using their intelligence and accumulated
knowledge, they remained essentially tropical animals despite the fact that
they were no longer living only in the tropics. However, natural
selection continued to select for increased brain size and presumably
intelligence. This pattern of culture altering natural selection
accelerated dramatically with the evolution of modern humans. Today, most
of us live in cities and towns that are essentially unnatural environments and
the rate of culture change has accelerated dramatically. We have occupied
most environmental zones on land, and yet we are still essentially tropical
animals physically. As a result, we perish rapidly if our cultural
technology is taken away from us in environments in which the temperature drops
to freezing.
|
Becoming
Human: Part 2--Nova episode on the biological and cultural evolution of Homo erectus. To return here, you must click the "back" button on your browser program. (length = 51 mins 27 secs) |
Practice Quiz for Early Human Culture
The first stone tool manufacturing and use was probably done
by early transitional humans in East Africa 4.5 million years ago.
## WRONG --> The
first stone tools were made in East Africa, but not until about 2.5-2.4 million
years ago. Please try again.
Which of the following tool traditions came first?
|
Acheulean
|
||
|
b)
|
Oldowan
|
|
|
c)
|
Habilian
|
|
## CORRECT --> Oldowan tools were first made by Homo
habilis and possibly late gracile australopithecines 2.5 million years ago in
Ethiopia and possibly other areas of East Africa.
Oldowan Tradition flake tools were probably used mostly for:
|
hammering other rocks to make core tools
|
||
|
b)
|
butchering animals
|
|
|
c)
|
making necklaces
|
|
## CORRECT --> Oldowan flakes were used for tasks such as
piercing, cutting, and scraping in butchering animals. These flake tools were likely the most
important Homo habilis and early Homo erectus
artifacts.
Which of the following statements is true of the first convincing evidence of fire use by humans?
|
It was associated with Homo erectus.
|
## CORRECT --> By 780,000-400,000 year ago, some late
Homo erectus had begun cooking meat and probably vegetable foods in fires
that they had started. This would have
been an important tool in migrations to the colder temperate regions of
Eurasia.
|
|
|
b)
It was associated with Homo habilis.
c)
d)
It was about 100,000 years ago .
|
||
The most well known Acheulean Tradition stone tool was a:
|
a) hand ax
|
|||
|
b)
|
spear
|
||
|
c)
|
meat cleaver
|
||
CORRECT --> Hand axes were rock cores or large flakes
that were worked by percussion flaking to an elongated oval shape with one
pointed end and sharp edges on the sides. They were multipurpose tools used for
light chopping of wood, digging up roots, and butchering.
Which of the following statements is true of major Homo erectus fossil sites by 400,000 years ago?
|
a)
|
They usually have only a few stone tools.
|
||||||||||||||||||||||||||||||||
|
b)
|
They usually have very little evidence of meat eating.
|
||||||||||||||||||||||||||||||||
|
c)
|
They have been found only in tropical regions of the
world.
|
||||||||||||||||||||||||||||||||
|
d)
|
none of the above
|
||||||||||||||||||||||||||||||||
# CORRECT --> All of the above statements are wrong. Look at the other answers for explanations.
A Beautiful Observation of Homo
erectus
Eva
em. rb. Eva a
13, 500 year old teenager {5-13-2016}
CD: 5/13/2016
There are 4 new documentaries made by NOVA that are
recently published July 17, 2015. I've watched all of them and I saw very
little that was truly new with the exceptions Eva and the new theory that Homo sapiens didn’t kill off Neanderthals
but interbred with them. Eva, discovered
in an underground cave in Yucatan
Peninsula Mexico is by far more interesting and it is covered in the first part ( 8
minutes) of this “First Peoples Americas“video. Mexican archaeologists have been studying these vast
underwater caves since 2008 and discovered 8 skeletons from this cave system.
It is the largest find in North America.
The human family tree starts 2 ½ Mya with Lucy. Unjtil that time wee were more ape than human.
Archaic humans. Argon dating[1]
[i]
Among the best-known techniques
are radiocarbon dating, potassium-argon dating, Argon–argon
dating. and uranium-lead dating.
Description of archaic skull: modern
humans developed their faces first and then their cranium. Can interbreed as
long as they've had a common ancestor within the past 2 My this I s a rule that applies to all primates including humans.
Modern humans have been mov ing out of
Africa for 100 Ky, but Archaic humans
have been moving out of Africa for 1 ½ My
There is also
some TEXT that interests me at the bottom of this email.
NOVA - First Peoples
4 videos
Published on Feb 27, 2016
14:40
–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™
–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™
Published on Jul 8, 2015
5:03
–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™–—˜™
Opposable
Thumb which allows our thumb to work in opposition to all our other fingers.
First
Peoples - Americas | PBS NOVA | HD Documentary | HD
720P Documentary
Published on Jul 17, 2015
720P Documentary
Published on Jul 17, 2015
As early humans spread out across the world, their toughest challenge was colonizing the Americas because a huge ice sheet blocked the route. It has long been thought that the first Americans were Clovis people, who arrived 13,000 years ago. But an underwater discovery in Yucatan Mexico of a girl now called Eva suggests people arrived earlier — coming by boat, not on foot.
First Peoples
Asia 49:50
First Peoples
Australia 54:42
|
Archaeologists
Find Earliest Evidence of Humans Cooking With Fire
 |
 |
|
At the base of a
brush-covered hill in South Africa’s Northern Cape province, a massive stone
outcropping marks the entrance to one of humanity’s oldest known dwelling
places. Humans and our apelike ancestors have lived in Wonderwerk Cave for 2
million years — most recently in the early 1900s, when a farm couple and
their 14 children called it home. Wonderwerk holds another distinction as
well: The cave contains the earliest solid evidence that our ancient human
forebears (probably Homo erectus) were using fire.
Like many archaeological
discoveries, this one was accidental. Researchers weren’t looking for signs
of prehistoric fire; they were trying to determine the age of sediments in a
section of the cave where other researchers had found primitive stone tools.
In the process, the team unearthed what appeared to be the remains of
campfires from a million years ago — 200,000 years older than any other firm
evidence of human-controlled fire. Their findings also fanned the flames of a
decade-old debate over the influence of fire, particularly cooking, on the
evolution of our species’s relatively capacious brains.
At Wonderwerk, Boston
University archaeologist Paul Goldberg — a specialist in soil
micromorphology, or the small-scale study of sediments — dug chunks of compacted
dirt from the old excavation area. He then dried them out and soaked them in
a polyester resin so they would harden to a rocklike consistency. Once the
blocks solidified, researchers sawed them into wafer-thin slices. The
“eureka” moment came later, as the slices were examined under a microscope at
Israel’s Weizmann Institute. “Holy cow!” Goldberg exclaimed. “There’s ashes
in there!”
He and his colleagues saw
carbonized leaf and twig fragments. Looking more closely, they identified
burned bits of animal bones as well. The bones’ sharp edges, and the
excellent preservation of the plant ash, indicated that neither wind nor rain
had ushered in the burnt material. The burning clearly had occurred inside
the cave.
Then
team member Francesco Berna subjected the sample to a test called Fourier
transform infrared microspectroscopy (FTIR), which analyzes a material’s
composition by measuring the way it absorbs infrared waves. Often used in
crime labs to identify traces of drugs and fibers, FTIR can also determine
the temperature to which organic matter has been heated — and Berna is among
the first to adapt it for archaeology. When he ran an FTIR analysis on one of
the sediment slices, the sample’s infrared signature showed that the cave
material had been heated to between 750 and 1,300 degrees Fahrenheit. That
was just right for a small fire made of twigs and grasses.
When the team announced its
findings in April 2012, it added fuel to a controversy that’s been smoldering
since 1999. That year, influential primatologist Richard Wrangham proposed a
theory of human origins called the “cooking hypothesis.” Wrangham aimed to
fill a gap in the story of how early hominins like Australopithecus —
essentially, apes that walked upright — evolved into modern Homo sapiens.
Evolutionary science shows that our distant progenitors became bipedal 6
million to 7 million years ago. Archaeologists believe early hominins evolved
bigger brains as they walked, took up hunting and developed more complex
social structures. That process led to the emergence of Homo habilis, the
first creature generally regarded as human, 2.3 million years ago. Yet H.
habilis’ brain was only moderately larger than Australopithecus’,
and its body retained many apelike features. No one knows why, just 500,000
years later, a radically more advanced species —Homo erectus —
emerged. Its brain was up to twice the size of its predecessor’s, its teeth
were much smaller, and its body was quite similar to ours.
Wrangham credits the
transformation to the harnessing of fire. Cooking food, he argues, allowed
for easier chewing and digestion, making extra calories available to fuel
energy-hungry brains. Firelight could ward off nighttime predators, allowing
hominins to sleep on the ground, or in caves, instead of in trees. No longer
needing huge choppers, heavy-duty guts or a branch swinger’s arms and
shoulders, they could instead grow mega-craniums. The altered anatomy
of H. erectus, Wrangham wrote, indicates that these beings, like
us, were “creatures of flame.”
There was one major problem
with this hypothesis, however: Proving it would require evidence of
controlled fire from at least 1.8 million years ago, when the first H.
erectus appeared.
The clues indicating early
use of fire tend to be subtle; it’s easy to miss them, but it’s also easy to
see them when they’re not really there. What looks like charring on a rock or
bone, for example, often turns out to be staining from minerals or fungus.
And high-tech analytic techniques don’t always banish the ambiguity.
In recent decades, a number
of sites have vied for the title of earliest human-controlled fire. At Koobi
Fora and Chesowanja, both in Kenya, small patches of reddened soil were found
in areas containing stone tools up to 1.5 million years old. To try to prove
that Early Stone Age campfires caused the discoloration, researchers in the
1980s and 90s used techniques such as magnetic susceptibility analysis and
thermoluminescence dating. The first tool detects burned earth by gauging
fluctuations in its magnetic field; the second determines how long ago an
object was heated by measuring the photons it emits when baked in a lab.
Although these methods showed that burning had occurred, the evidence is
simply too sparse to convince most archaeologists that humans — not wildfires
or lightning — were responsible.
Another promising site is a
South African cave called Swartkrans, where archaeologists in the ’80s found
burned bones in a section dating between 1 million and 1.5 million years ago.
In 2004, Williams College chemist Anne Skinner analyzed the bones using
electron spin resonance, which estimates the temperature to which an artifact
has been heated by measuring molecular fragments called free radicals. She
determined that the bones had reached at least 900 degrees — too hot for most
wildfires, but consistent with a campfire. But since the cave has a gaping
mouth and a downward-sloping floor, naysayers argue that the objects might
have washed in later after being burned outside.
Until the Wonderwerk Cave
find, Gesher Benot Ya’aqov, a lakeside site in Israel, was considered to have
the oldest generally accepted evidence of human-controlled fire. There, a
team of scientists found traces of numerous hearths dating to between 690,000
and 790,000 years ago. A wide range of clues made this site convincing,
including isolated clusters of burned flint, as if toolmakers had been
knapping hand axes by several firesides. The team also found fragments of
burned fruit, grain and wood scattered about.
Then came Wonderwerk. The
ash-filled sediment that Goldberg and Berna found came from a spot
approximately 100 feet from the entrance to the tunnel-like cave, too far to
have been swept in by the elements. The team also found circular chips of fractured
stone known as pot-lid flakes — telltale signs of fire — in the same area.
These clues turned up throughout the million-year-old layer of sediment,
indicating that fires had burned repeatedly at the site.
Does that mean fire drove the
evolution of H. erectus? Is the cooking hypothesis correct? The
occupants who left these ashes at Wonderwerk lived nearly a million years
after the emergence of H. erectus. Goldberg and Berna point out
that it’s unclear whether the cave’s inhabitants knew how to start a fire
from scratch or depended on flames harvested from grass fires outside the
cave. If they were eating barbecue, it may have been only an occasional
luxury. Whether that could have had an impact on human development remains an
open question.
|
Genetic eve
Bozeman, Anderson,
[1]
Argon–argon dating
From Wikipedia, the free encyclopedia
Argon–argon (or 40Ar/39Ar) dating is
a radiometric dating method invented to
supersede potassium-argon (K/Ar) dating in
accuracy. The older method required splitting samples into two for separate
potassium and argon measurements, while the newer method requires only one rock
fragment or mineral grain and uses a single measurement of argon
isotopes. 40Ar/39Ar dating relies on neutron
irradiation from a nuclear reactor to convert a stable form of potassium (39K) into the
radioactive 39Ar. As long as a standard of known age is co-irradiated with
unknown samples, it is possible to use a single measurement of argon isotopes
to calculate the 40K/40Ar* ratio, and thus to
calculate the age of the unknown sample. 40Ar* refers to the
radiogenic 40Ar, i.e. the 40Ar produced from
radioactive decay of 40K. 40Ar* does not
include atmospheric argon adsorbed to the surface or inherited through
diffusion and its calculated value is derived from measuring the 36Ar
(which is assumed to be of atmospheric origin) and assuming that 40Ar
is found in a constant ratio to 36Ar in atmospheric gases.
Contents
·
1Method
[i] Radiometric dating
Together with stratigraphic
principles, radiometric dating methods are used in geochronology to
establish the geological time scale.[3] Among
the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating. By allowing the
establishment of geological timescales, it provides a significant source of
information about the ages of fossils and
the deduced rates of evolutionary change. Radiometric dating is also used
to date archaeological materials, including ancient
artifacts.
