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.
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| 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.
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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.
History
of Discovery
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Eugene Dubois (1858-1940) |
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In
the late 19th century, our knowledge of human fossil ancestors did not go back beyond that
of the Neandertals
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.
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.
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.
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.
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| Davidson Black
(1884-1934) |
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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
.
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-1930's). The bones of
50 individual
Homo erectus were eventually found there.
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| "Peking Man" skull | |
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. 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.
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| "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 as Homo 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-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.
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Important Homo erectus Sites |
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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. |
