Tuesday, July 5, 2016


1sci. ev. rsh. A Beautiful Observation of Homo Erectus{2-2-2016}
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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

šœšœšœšœšœšœ
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 click this icon to hear the preceding term pronounced (literally "upright human").  However, a few researchers split them into two species--Homo ergaster click this icon to hear the preceding term pronounced (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.
photo of a Homo erectus skull from Java (side view)

photo of a Homo ergaster skull from Afrcia (side view)
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.Map of the likely Ultimate Range of Homo erectus with the Lake Turkana Region of East Africa highlighted

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 click this icon to hear the preceding term pronounced.  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.
Family tree of early humans


History of DiscoveryPithecanthropus erectus 

photo of Eugene DuboisEugene 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 click this icon to hear the preceding term pronounced.  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 click this icon to hear the preceding term pronounced (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 click this icon to hear the preceding term pronounced (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.

photo of Davidson Black

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 click this icon to hear the preceding term pronounced
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 click this icon to hear the preceding term pronounced(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 photo of the 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"
photo of the Lake Turkana Boy skeleton

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


Map of the Important Homo erectus SitesNote: 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

http://anthro.palomar.edu/homo/images/Homo_erectus_reconstruction.gif

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 click this icon to hear the preceding term pronounced 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 click this icon to hear the preceding term pronounced).  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.
photo comparison of Homo erectus and Homo sapiens skulls with the supraorbital tori indicated
Homo erectus            
(from Java)              
  Homo sapiens   
(modern human)


photo of the upper teeth of a Homo erectus with the shovel-shaped incisors highlighted


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.
click this icon to hear the following audio interview  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 click this icon to hear the preceding term pronounced.  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.
click this icon in order to see the following video  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 on
        your browser program.              (length = 4 mins 19 secs)
http://anthro.palomar.edu/homo/images/horn.gif  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

«««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


Epoch
Climate
Years Ago (approximate)
Regional Name for Climate Stage
European Alps
North America
Holocene
interglacial
10,000 to the present


Pleistocene
glacial
110-70,000 to 12-10,000
Würm
Wisconsin
interglacial
130-125,000 to 110,000
Riss-Würm
Sangamon
glacial
200,000 to 130-125,000
   Riss
Illinoian
interglacial
380-300,000 to 200,000
   Mindel-Riss
   Yarmouth **
glacial
455-410,000 to 380-300,000
   Mindel
   Kansan **
interglacial
620,000 to 455-410,000
   Günz-Mindel
   Aftonian **
glacial
680,000 to 620,000
   Günz
   Nebraskan **
Evidence of glacial and interglacial episodes during the early Pleistocene
is less clear.  However, it is believed that there were 2 or more glacials with
intervening interglacials.  Between the Pleistocene and the preceding
Pliocene Epoch was a long period of gradual cooling.
Pliocene
5.3-2.6 million years ago--mostly warmer conditions than the Pleistocene


     

Note on Ice Ages

http://anthro.palomar.edu/homo/images/Pleistocene_temp_change_graph.gifhttp://anthro.palomar.edu/homo/images/map_of_glaciations.gifThese 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)
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.

http://anthro.palomar.edu/homo/images/vidcam.gif  Likely effects of extreme cold conditions on human evolution
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        (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)
graph of the 4 major cold periods over the Last 1/2 billion years
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.

photo of an Odowan Tradition chopper

Oldowan tradition core tool (chopper)
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 click this icon to hear the preceding term pronouncedtools 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.
click this icon to hear the following audio interview 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 click this icon to hear the preceding term pronounced, 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 click this icon to hear the preceding term pronounced.  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 click this icon to hear the preceding term pronouncedtools.  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.
photo of 2 Acheulean Tradition hand axes
 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.
drawing of percussion flaking a hand ax with a hammerstone
drawing of percussion flaking a hand ax with a soft hammer (bone in this case)  
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.
map showing the geographic range of the Acheulean Hand Axe Tradition
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 click this icon to hear the preceding term pronounced.  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.
click this icon in order to see the following video  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)

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
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



http://s.ngm.com/2006/03/human-journey/img/boy-painted-face-615.jpghttp://ecx.images-amazon.com/images/I/51U53CclLwL._AC_UL320_SR228,320_.jpgEva

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]

14:40 jabo ehood Watch full video at www.docuvevo.com
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.
Published on Feb 27, 2016
14:40
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 Nova׃ Dawn of Humanity 2015   1:45;45
˜˜˜˜˜˜˜˜
Published on Jul 8, 2015
5:03
˜˜˜˜˜˜˜˜
Bozeman Anderson  LS4C Adaptation   8:04
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

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
Discover Magazine: The magazine of science, technology, and the future
cave-1

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/39Ardating 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
·         2Age equation
·         3Relative dating only
·         4Applications
·         5Recalibration
·         6See also
·         7References
·         8External links




[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 datingpotassium-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.