We have established that the big event in terms of the development of
a global Bronze Age economy was the decision to build the Great
Pyramid in Egypt around 2420 BC. It effectively united and
established far flung trade factories and likely colonies. Many new
imitative civilizations naturally arose from these examples on the
ground.
The three predecessor civilizations were explicitly the Egyptian, the
Mesopotamian and the Harappan. They all show us extensive
prehistories and large populations already on the ground. The
.largest appears to be that of the Harappan.
Other large populations likely also existed in North Africa and
throughout the Middle East.
The argument is well made here that the Harappan were driven out by
climatic failure in their homeland.
What is poorly understood is the cause of climate change throughout
the entirety of the region. I am pretty well convinced that chronic
deforestation did most of the damage driven by fuel needs as
populations climbed. Where the land was well vegetated but dry, this
became a vicious cycle of drying and burning. Most likely the final
insult was the depredations of the lowly goat which kept recovery
from occurring. Eventually the water table would disappear and the
population would be forced to move on.
The Huge Ancient
Civilization's Collapse Explained
Charles Choi,
LiveScience Contributor
Date: 28 May 2012
Time: 10:01 PM ET
The Harappan
civilization once extended across the plains of the Indus River from
the Arabian Sea to the Ganges.mysterious fall of the largest of the
world's earliest urban civilizations nearly 4,000 years ago in what
is now India, Pakistan, Nepal and Bangladesh now appears to have a
key culprit — ancient climate change, researchers say.
Ancient Egypt and
Mesopotamia may be the best known of the first great urban cultures,
but the largest was the Indus or Harappan civilization. This culture
once extended over more than 386,000 square miles (1 million square
kilometers) across the plains of the Indus River from the Arabian Sea
to the Ganges, and at its peak may have accounted for 10 percent of
the world population. The civilization developed about 5,200 years
ago, and slowly disintegrated between 3,900 and 3,000 years ago —
populations largely abandoned cities, migrating toward the east.
"Antiquity knew
about Egypt and Mesopotamia, but the Indus civilization, which was
bigger than these two, was completely forgotten until the 1920s,"
said researcher Liviu Giosan, a geologist at Woods Hole Oceanographic
Institution in Massachusetts. "There are still many things we
don't know about them." [Photos: Life and Death of Ancient
Urbanites]
Nearly a century ago,
researchers began discovering numerous remains of Harappan
settlements along the Indus River and its tributaries, as well as in
a vast desert region at the border of India and Pakistan. Evidence
was uncovered for sophisticated cities, sea links with Mesopotamia,
internal trade routes, arts and crafts, and as-yet undeciphered
writing.
"They had cities
ordered into grids, with exquisite plumbing, which was not
encountered again until the Romans," Giosan told LiveScience.
"They seem to have been a more democratic society than
Mesopotamia and Egypt — no large structures were built for
important personalitiess like kings or pharaohs."
Like their
contemporaries in Egypt and Mesopotamia, the Harappans, who were
named after one of their largest cities, lived next to rivers.
"Until now,
speculations abounded about the links between this mysterious ancient
culture and its life-giving mighty rivers," Giosan said.
Now Giosan and his
colleagues have reconstructed the landscape of the plain and rivers
where this long-forgotten civilization developed. Their findings now
shed light on the enigmatic fate of this culture.
"Our research
provides one of the clearest examples of climate change leading to
the collapse of an entire civilization," Giosan said. [How
Weather Changed History]
The researchers first analyzed satellite data of the landscape
influenced by the Indus and neighboring rivers. From 2003 to 2008,
the researchers then collected samples of sediment from the coast of
the Arabian Sea into the fertile irrigated valleys of Punjab and the
northern Thar Desert to determine the origins and ages of those
sediments and develop a timeline of landscape changes.
"It was
challenging working in the desert — temperatures were over 110
degrees Fahrenheit all day long (43 degrees C)," Giosan
recalled.
After collecting data
on geological history, "we could reexamine what we know about
settlements, what crops people were planting and when, and how both
agriculture and settlement patterns changed," said researcher
Dorian Fuller, an archaeologist with University College London. "This
brought new insights into the process of eastward population shift,
the change towards many more small farming communities, and the
decline of cities during late Harappan times."
Some had suggested
that the Harappan heartland received its waters from a large
glacier-fed Himalayan river, thought by some to be the Sarasvati, a
sacred river of Hindu mythology. However, the researchers found that
only rivers fed by monsoon rains flowed through the region.
Previous studies
suggest the Ghaggar, an intermittent river that flows only during
strong monsoons, may best approximate the location of the Sarasvati.
Archaeological evidence suggested the river, which dissipates into
the desert along the dried course of Hakra valley, was home to
intensive settlement during Harappan times.
"We think we
settled a long controversy about the mythic Sarasvati River,"
Giosan said.
Initially, the
monsoon-drenched rivers the researchers identified were prone to
devastating floods. Over time, monsoons weakened, enabling
agriculture and civilization to flourish along flood-fed riverbanks
for nearly 2,000 years.
"The insolation —
the solar energy received by the Earth from the sun — varies in
cycles, which can impact monsoons," Giosan said. "In the
last 10,000 years, the Northern Hemisphere had the highest insolation
from 7,000 to 5,000 years ago, and since then insolation there
decreased. All climate on Earth is driven by the sun, and so the
monsoons were affected by the lower insolation, decreasing in force.
This meant less rain got into continental regions affected by
monsoons over time." [50 Amazing Facts About Earth]
Eventually, these
monsoon-based rivers held too little water and dried, making them
unfavorable for civilization.
"The Harappans
were an enterprising people taking advantage of a window of
opportunity — a kind of "Goldilocks civilization," Giosan
said.
Eventually, over the
course of centuries, Harappans apparently fled along an escape route
to the east toward the Ganges basin, where monsoon rains remained
reliable.
"We can envision
that this eastern shift involved a change to more localized forms of
economy — smaller communities supported by local rain-fed farming
and dwindling streams," Fuller said. "This may have
produced smaller surpluses, and would not have supported large
cities, but would have been reliable."
This change would have
spelled disaster for the cities of the Indus, which were built on the
large surpluses seen during the earlier, wetter era. The dispersal of
the population to the east would have meant there was no longer a
concentrated workforce to support urbanism.
"Cities
collapsed, but smaller agricultural communities were sustainable and
flourished," Fuller said. "Many of the urban arts, such as
writing, faded away, but agriculture continued and actually
diversified."
These findings could
help guide future archaeological explorations of the Indus
civilization. Researchers can now better guess which settlements
might have been more significant, based on their relationships with
rivers, Giosan said.
It remains uncertain
how monsoons will react to modern climate change. "If we take
the devastating floods that caused the largest humanitarian disaster
in Pakistan's history as a sign of increased monsoon activity, than
this doesn't bode well for the region," Giosan said. "The
region has the largest irrigation scheme in the world, and all those
dams and channels would become obsolete in the face of the large
floods an increased monsoon would bring."
The scientists
detailed their findings online May 28 in the journal Proceedings of
the National Academy of Sciences
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