Ancient Tools: Searching for the First Americans
VOLUME 19, NUMBER 4, SPRING 2005 PDF
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Editor: John
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Contributing Writer: Susan
Ferris Hill
Ancient Tools: Searching for the First Americans
By John
H. Tibbetts
Small stone pieces excavated at the Topper site in Allendale County could be central to the story of Homo sapiens.
Some ancient Americans migrated to coastal South Carolina for the same
reasons that many northerners still relocate here today. They preferred
living near water and the seashore in a warm climate.
That’s an educated guess by Albert Goodyear, a University of South
Carolina archaeologist who has drawn international headlines for
excavating and interpreting artifacts at an archaeological site named
Topper located along the Savannah River in Allendale County. In May
2005, the USC archaeology team will continue excavating at Topper,
named for a local man who first showed Goodyear the site.
Goodyear’s findings at Topper have placed South Carolina in the middle
of a fierce debate about the origins of the first Americans. Now South
Carolina could become central to the changing story of Homo sapiens.
Thousands of years ago, when the area now known as South Carolina was
colder and dryer than today but more pleasant than farther north,
ancient Americans migrated to Topper, Goodyear says. “Topper may have
drawn people from all over the hemisphere simply because they were
looking to relocate in warmer climes.”
Early hunter-gatherers who used Topper were likely coast-dwellers, says
Goodyear. Ancient people may have lived in settlements along the South
Carolina shoreline most of the year, harvesting shellfish and fishing
and perhaps hunting marine mammals.
In the spring, they likely traveled inland along the Savannah River, a
major artery linking the Atlantic Ocean to the interior. They might
have netted migratory fish swimming upstream to spawn. On a river bluff
at the Topper site in Allendale County, early Americans broke open
cream-colored rock called chert. Chert is a glassy, flint-like stone
used to carve tools from antler, wood, and bone.
The Topper site was one of the best sources of chert in the region.
People from across eastern North America probably came to the Topper
chert quarry to make tools.
Scientists agree that early Americans used Topper as an important
tool-making site at least 13,000 years ago. But, in November 2004,
Goodyear, an expert on ancient tool-making, announced that testing
apparently showed that people were visiting Topper at least 50,000
years ago.
Goodyear’s team had found prehistoric burnt plant material from a
charcoal fire buried deep under layers of sediment. The burnt material
was sent to a laboratory in California, where its age was determined by
state-of-the-art radiocarbon techniques.
Small stone tools and flakes—tool-making byproducts—were found in the
same geological level as the burnt material. Scientists cannot date
chert; instead, they rely on testing adjacent organic material or
sediments.
Goodyear’s 50,000-year announcement startled his colleagues because it
does not jibe with current scientific understanding of when the
earliest Americans arrived on this continent.
Today’s archaeological evidence strongly indicates an arrival after
about 18,000 years ago, at the earliest. Even so, the first Americans’
arrival date is a moving target. Just a decade ago, scientists argued
adamantly that Americans did not migrate to the Western Hemisphere
until 13,500 years ago.
American archaeology is changing quickly because researchers are
finding new evidence of earlier explorers of the New World.
Nevertheless, a 50,000-year date at Topper shoots off the charts to
most experts, Goodyear acknowledges.
“Until we dig (more artifacts) and publish (results), I doubt you’ll
get many people to comment positively on that,” says Goodyear. “I’m
sitting out there on a limb, and we have a lot of work to do.”
Nevertheless, Goodyear’s team at Topper has also unearthed numerous
small tools in sediment dated by optically stimulated luminescence at
an age of 16,000 to 20,000 years old.
Although also controversial, these ancient tools could fit neatly into
a new model of the first Americans’ migration to this continent. If
eventually accepted by the research community, the tools would help
further undermine a scientific consensus that lasted for generations.
From the 1930s to the late 1990s, archaeologists believed that the
first Americans were big-game hunters who arrived in the New World from
the Bering land bridge that connected Siberia and Alaska about 13,500
years ago. Ancient hunters followed mammoths and other big game into
Canada south along the eastern slope of the Rocky Mountains and then
quickly spread across the Great Plains, according to traditional
archaeological theory.
Archaeologists called them Clovis people for their beautiful,
sophisticated, and distinctively sculpted spear points first discovered
near Clovis, New Mexico, in 1932. Numerous spear points were located
near mammoth bones, suggesting that the weapons were used to kill the
animal. Clovis points have since been found in every state in the lower
48 and every county in South Carolina.
For decades, virtually every knowledgeable scientist accepted the
Clovis-first theory—that Clovis people were the first Americans.
Goodyear himself believed it until the late 1990s. Only apparent fools
thought otherwise. “If you were an archaeologist who claimed to find a
pre-Clovis site,” says Goodyear, “it was tantamount to saying you just
saw Elvis leave Burger King.”
But this theory is wrong and should be abandoned, says Michael B.
Collins, an archaeologist at the University of Texas. “We’ve
demonstrated fatal flaws in Clovis-first. We’ve got to come up with a
replacement theory.”
In recent years, archaeologists have excavated human artifacts that are
older than Clovis, or are the same age but reflect a different way of
life. Various sites, in both North and South America, prove that Clovis
were not the first Americans.
Now Goodyear says he also has strong evidence proving that people were
visiting at Topper 16,000 to 20,000 years ago, working with small chert
tools such as chisels and scrapers. Microscopic evidence, he argues,
shows signs of purposeful scratching and polishing—indications that the
artifacts were manmade.
A skeptical colleague, however, says that Goodyear has jumped to
conclusions. Stone pieces older than about 13,500 years old at Topper
are not tools, says Collins. Instead, natural processes fractured them.
“Many of us have looked at these ‘tools,’ and everything I’ve seen is
absolutely a natural fracture.”
Most archaeological sites in North America claiming pre-Clovis tools
have failed to gain scientific acceptance. Researchers decided that
freezing and thawing, fires, or other natural events fractured stone
pieces that only looked to some like tools.
Nevertheless, two pre-Clovis sites in North America—one in Pennsylvania
called Meadowcroft Rockshelter and another in Virginia called Cactus
Hill—have gained significant scientific acceptance in recent years.
Both sites indicate human occupation before 13,500 years ago.
Now Goodyear wants Topper added to this short list of solid pre-Clovis candidates.
Topper tools dated 16,000 to 20,000 years old have stood up to scrutiny
by some experts. “I’ve had people who are really expert at analysis
come to look at (the stone pieces), and most of them agree that they
are tools,” says Goodyear. “Not all archaeologists are adept at looking
at some of the subtle features” of artifacts.
Joel Gunn, an archaeological consultant based in Chapel Hill, North
Carolina, says Topper’s pre-Clovis stones were apparently shaped by
human hands. “Probability favors that they are tools. Al has a
convincing model for how pre-Clovis people would have used a tool kit.”
Bradley Lepper, an archaeologist with the Ohio Historical Society, also
backs up Goodyear’s claim. “There are repetitive patterns of industry.
They were systematically reproducing repeated forms, these little
bladelets. I don’t know of any natural mechanisms that would
systematically form so many (pieces) in the number and consistency that
he is finding them. If nature were incidentally making these things,
you would expect (their forms) to look more random. Al is persuading
many of us that, yes, they are tools, and that people were in America
at a surprisingly early date.”
Another problem with many pre-Clovis sites, critics say, is that
natural items (such as burnt plant material) dated by radiocarbon
techniques do not accurately reflect their real age. Natural
processes—floods for example—could have mixed up loose materials from
various eras, so that newer tools could have pushed into older
sediments.
Topper’s geology, however, has remained intact throughout its sediment
layers. Moreover, several feet of sediment distinctly separate newer
Clovis layers from older pre-Clovis ones, says Lepper. As a result,
mixing was not possible.
So while many skeptics accept Goodyear’s analysis of Topper’s geology
and dating, their doubts focus on the question of whether humans
crafted the stone pieces. Goodyear argues the tools are human
artifacts; some skeptics say they are not.
Only a decade ago, archaeologists thought they knew when and how the
first Americans arrived here. Today, that’s no longer true; there seem
to be more questions than answers. The story that once was so clear and
simple could have a complex new beginning.
Researchers are working toward a new multi-entry model to explain the
migration of the first Americans. Now it seems likely that the first
Americans were coastal people, not inland big-game hunters.
The earliest Americans were probably fishermen, shellfish harvesters,
and hunters of marine mammals, who migrated in numerous waves.
From East Asia they could have walked north along ancient coastlines or
rowed small canoes made of sealskin. Reaching the southern coast of the
Bering land bridge, they could have migrated eastward until they
reached North America. Then they could have traveled south along the
Northwest Coast of Alaska, British Columbia, and Washington state, down
to California and Mexico, and then Central America and South America.
Small bands of humans exploring and colonizing unknown continents, says
Goodyear, probably would have used seashores and major rivers to move
around and harvest resources. They would have known how to find
shellfish, finfish, and marine mammals along the coast. “I think the
coast had to play an important role in transcontinental migrations,”
says Goodyear.
Could the first Americans have arrived here from Europe or Africa? No.
Genetic evidence proves that East Asians populated the Americas before
Europeans began arriving in the sixteenth century.
Linguistic evidence also shows that the first Americans came from East
Asia. “There are structural properties that are common in (language) in
the Americas that are common in Asia, and rare elsewhere,” says Johanna
Nichols, a linguist and professor of Slavic languages at the University
of California at Berkeley.
The timing and the routes to America, however, remain a mystery. “We
don’t know how the Americans were peopled,” says University of Oregon
archaeologist Jon Erlandson. “We don’t know when the Americas were
first colonized. Ten years ago, many people thought it was all figured
out. Now we find ourselves in a completely different scenario, with
multiple different hypotheses calling for attention. It’s a much more
wide-open field, which is really exciting.”
THE COASTAL-MIGRATION MODEL
People physically like us evolved in Africa perhaps as early as 160,000
years ago. Still, there was another evolutionary stage yet to come.
About 80,000 to 50,000 years ago, Homo sapiens began developing
radically improved technologies, making more diverse tools, which
allowed them to hunt more efficiently. Scholars believe that these
technologies were combined with more sophisticated art forms and
language, which spawned a genetic and cultural revolution in human
consciousness that geographer Jared Diamond has called “The Great Leap
Forward.”
Suddenly, people who looked like us began to think like us, too. They became innovators and explorers on an unprecedented scale.
Armed with new cognitive and social capabilities, fully modern humans
for the first time began leaving Africa. Some populations moved into
Central Asia about 50,000 years ago and into Europe about 40,000 years
ago.
But if fully modern people were just beginning to reach Central Asia
about 50,000 years ago, how could they have arrived at Topper at about
the same time? One possible answer is that they moved with blazing
speed along coastlines across southern and eastern Asia to the New
World.
Fully modern people apparently did migrate swiftly eastward about
50,000 years ago from Africa along the southern shoreline of Asia, the
“coastal superhighway,” writes population geneticist Spencer Wells in
his 2002 book The Journey of Man.
It’s common for hunter-gatherer bands to move several miles a year,
following animals, searching for water or plants, or getting stones for
tool-making. In this fashion, people could have traversed the southern
Asian coastline in a few thousand years.
Coastal migration along the southern Asian coast would have been much
faster than traveling inland to Central Asia. Coastal hunter-gatherers
did not have to climb mountains or adjust to dramatically different
weather and food sources. Searching for food and water along a
shoreline would have required the same tools and techniques in coastal
Africa, India, or East Asia.
When hunter-gatherers reached the southeastern corner of Asia, they
apparently looked to the sea. Recent discoveries prove that Homo
sapiens built some kind of watercraft—probably logs lashed together—to
sail or row across 60 miles of ocean from Southeast Asia to colonize
Australia about 50,000 years ago. At that time, sea levels were much
lower, so coastlines of the two continents were closer than they are
today. But people did need boats or rafts to reach Australia.
At Lake Mungo in southeastern Australia, University of Melbourne
geomorphologist Jim Bowler and his colleagues have dated remains of an
anatomically modern man and a woman at about 40,000 years old. Humans
had been living at Lake Mungo at least 6,000 years previously.
These early Australians were probably coastal people who moved
seasonally inland following a prehistoric river to Lake Mungo, now a
semi-arid landscape. Ancient artifacts found there indicate that the
first Australians hunted small game, gathered mussels and other
shellfish from the lake, and fished for cod and perch, possibly using
nets.
From Southeast Asia, people also began exploring by boat offshore
islands in the far western Pacific. About 35,000 years ago, ancient
mariners rowed or sailed across 100 miles of ocean to settle islands
that are now part of Papua New Guinea.
The earliest maritime cultures therefore got established in
warm-climate regions offshore from Southeast Asia. “There is
considerable evidence for maritime activity on the western side of the
Pacific,” says Erlandson.
But if the first Americans arrived here via a coastal route, they must
have been adapted to a temperate or arctic maritime climate, which
would have been much more challenging than the climate of Southeast
Asia and Australia. That’s because the first Americans almost certainly
traveled across the northern Pacific region during an era much colder
than today.GLACIER MELTING CLUES
The likeliest period when the first Americans arrived in the Western
Hemisphere was not long after the last glacial maximum when continental
glaciers were beginning to melt.
Glaciers at their greatest extent covered nearly a third of the world’s
landmass 20,000 years ago, reaching as far south as New York City.
Following this deep freeze, the Earth’s climate saw extreme variations,
but its overall trend was warmer for the next 12,000 years.
About 15,000 years ago, ancestors of the Clovis people were probably
living on the Bering land bridge between Siberia and Alaska. But two
continental glaciers in Canada blocked their entry to the Americas. As
warming accelerated 13,500 years ago, the glaciers began to melt and
separate in northwestern Canada.
Subsequently, the Clovis people traveled south through an ice-free
corridor to the eastern foothills of the Rocky Mountains, according to
traditional archaeological theory. They could not have migrated south
through this ice-free corridor any earlier than 13,500 years ago;
glaciers blocked their way.
The Clovis-first theory remained dominant until a scientific
breakthrough suddenly damaged its credibility and changed the direction
of American archaeology.
In 1997, Thomas D. Dillehay, an archaeologist at Vanderbilt University,
and his colleagues distributed a site report on their excavation of an
ancient settlement called Monte Verde about 40 miles from the Pacific
Ocean in Chile. Dillehay’s team had excavated the remains of several
ancient structures, stone and wood implements, and clay-lined hearths
that contained charcoal and burned plant foods. All were buried in the
same geological layer under a muddy bog.
Radiocarbon testing, adjusted to calendar years, showed that Monte
Verde materials were more than 14,500 years old. A committee of experts
visited the site in 1997 and verified Monte Verde’s authenticity.
The discovery at Monte Verde meant that humans were living in the
southern cone of South America at least a thousand years before the
Clovis people could have traveled south through the ice-free corridor
in Canada. Many archaeologists had to drop their pet theory and
acknowledge that Clovis people were not first in the Americas.
When the Clovis-first orthodoxy fell apart, some scholars who had
believed in it began re-examining why ice-age hunters would have
pursued big game for some two thousand miles south through a narrow gap
between giant ice sheets in Canada about 13,500 years ago.
“The corridor was an unbelievably hostile environment for humans,” says
Collins, who before Monte Verde accepted Clovis-first orthodoxy. “What
would pull people into that? What were they chasing? The biggest
megafauna there were probably mosquitoes.”EARLY BOATS
Archaeologists cast around for another possible route into the Americas—and a coastal pathway made sense.
Scientists are now testing the coastal-entry theory of migration first
proposed by Knut Fladmark of Simon Fraser University almost 30 years
ago. In recent years, increasing numbers of archaeologists have become
supporters of the theory.
The theory is based on the fact that coasts usually have milder
climates than inland places at the same latitude. As the ice age wound
down, glaciers melted and withdrew sooner along most coastlines than
inland areas. Maritime warming would have allowed an earlier migration
of animals and people along coastlines into the Americas.
There were only two methods with which coastal people from Asia could
have migrated along shorelines to North America. They could have walked
the entire distance. Or they could have used boats.
Many recent studies on the glacial history, climatic history, sea-level
changes, and archaeology and paleoecology of the Northwest Coast show
that a coastal route was open before an inland corridor, says Carole
Mandryk, a geoarchaeologist at Harvard University. “The Northwest Coast
was available (for migration) at least two thousand years earlier than
the (ice-free inland) corridor.”
By 16,000 years ago, glaciers along the shoreline route from Asia to
America had retreated inland. The coasts by then were covered in grass
and trees and rich in wildlife. As a result, people could have walked
from northeastern Asia to North America and farther south to Monte
Verde on the west coast of South America by 14,500 years ago.
Or perhaps people built small boats tens of thousands of years ago in
East Asia and used them to travel to the New World. Glacier-free
refuges began to appear as early as 18,000 years ago along northern
Pacific coastlines. Migrants could have rowed boats from island to
island, refuge to refuge, to America.
In fact, an ancient Japanese maritime culture did exist at least 21,000
years ago. Seeking obsidian (a volcanic rock) for toolmaking, Japanese
at that time traveled by boat across open water about 35 miles to an
island in the Pacific Ocean east of present-day Tokyo. Ancient Japanese
were adapted to a climate resembling that of the far northern Pacific,
which was warmed by an ocean current from the south. Could early
Japanese have traveled along the coastline to the land bridge
connecting Asia and North America?
Traditional Inuit technology might provide an answer. Among some native
communities in Alaska, hunters still build large skin-on-frame canoes,
or umiaks, to catch sea mammals.
Instead of using sawn lumber for the umiak frame, ancient people could
have shaped driftwood with stone axes and scrapers. Bearded seal or
split walrus hides could have been sewn together and stretched over the
frame. These boats would have been tough, light, flexible, and capable
of carrying heavy loads.
Ancient Asian migrants on their route to America could have lived in
caves in coastal refuges or built dugout shelters covered with mammal
skins. Perhaps they burned driftwood or downed trees for fuel. They
could have dug for clams, gathered and dried seaweed, and hunted seals
and sea lions.
Maritime people did have boats off the North American West Coast at
least 13,000 years ago—or about the same time as Clovis people arrived.
Archaeologists have excavated shell middens dated to 12,000 to 13,000
years old in the Channel Islands off California, which could have only
been reached by boat from the mainland. The oldest human bones—a
woman’s—found in North America, excavated in the Channel Islands, are
about 13,000 years old.
“Paleoindians on the Channel Islands needed seaworthy boats to get
there,” says Erlandson. “They were on the Channel Islands about the
same time as Clovis, so this showed that paleoindians had boats that
were cruising about off the Pacific.”
The problem with the boat-migration model, says David Meltzer, an
anthropologist at Southern Methodist University, is that boats do not
exist in the archaeological record that far back. “We lack any evidence
of boats until the mid-Holocene times (5,000 to 6,000 years ago) along
the Northwest Coast and along the coast of Alaska. In the absence of
any evidence of boats whatsoever, you probably have them walking along
coastlines. The idea that people would be crossing entire oceans in the
rafting technology that would have been available in those days doesn’t
make a lot of sense to me.”
However, northern maritime Asians were probably not crossing large
stretches of open water but instead following the coastline, says
Mandryk. They could have traveled by watercraft over short distances,
stopping at glacier-free islands and coastal refuges along the way.
They were coastal people who could have lived off marine resources but
also hunted and fished inland along the banks of river valleys.
About 18,000 years ago, coastal hunter-gatherers could have used boats
to migrate across the land’s edge in the northern Pacific to reach
California. Then, in a matter of centuries, hunter-gatherers could have
moved south to Panama and crossed the isthmus and then followed the
coastline of the Gulf of Mexico to the East Coast of North America. It
seems likely that they could have thus arrived at Topper perhaps by
16,000 to 17,000 years ago.
Many questions remain, however. If the first Americans did arrive
several thousand years before Clovis, why haven’t archaeologists found
more evidence of them in North America? Only a small number of genuine
pre-Clovis sites exist in the Americas—and no human skeletons.
One reason may be that global warming following the last glacial
maximum 20,000 years ago drowned the evidence of coastal settlements.
When glaciers shrank in response to rising temperatures, huge amounts
of freshwater were released into the oceans. Sea levels rose and
swamped river valleys and coastal plains. Coastlines moved steadily
landward. The Bering land bridge between Asia and North America
disappeared under water.
The shoreline off Charleston 13,000 to 18,000 years ago was about 60 to
70 miles farther east than it is today, according to Paul Gayes, a
marine scientist at Coastal Carolina University. If there are any
ancient remains of villages off the South Carolina shoreline, they are
buried under 300 to 400 feet of seawater. With current technology, it’s
almost impossible to find where the earliest communities were located
along the ice-age coastlines of the Americas. The best ice-age coastal
sites exist in places like Monte Verde that were lifted by tectonic
activity above rising seas.
A NEW CONSENSUS?
Today, scholars are increasingly building a rough new consensus—that
numerous small-scale groups arrived in the Americas at various times.
They probably included hunter-gatherer bands that traveled through an
ice-free corridor, people who walked here along coastlines, perhaps in
tandem with seal-boat groups over many centuries, all from East Asia.
The Clovis people could have arrived in North America through an
ice-free corridor following a coastal migration. “There is a striking
correlation between the opening of the ice-free corridor and the
appearance of Clovis” artifacts in the archaeological record, says
Meltzer. Or perhaps there was a near-simultaneous Clovis-first
migration and a coastal migration. “You can have your cake and eat it,
too.”
But East Asians could not have migrated to North America as early as
50,000 years ago, as Goodyear’s “out-on-a-limb” preliminary findings at
Topper suggest, many experts say.
The earliest archaeological site where modern humans lived in
northeastern Siberia is only 29,000 years old. There is no evidence
that modern humans had the skills and tools enabling them to survive on
the land bridge in Arctic conditions between Asia and North America
earlier than 30,000 years ago.
“It’s incomprehensible to me that anything (human-made) at Topper could
be 50,000 years old,” says Mandryk. “You can’t have people migrating to
North America before they exist anywhere to migrate from.”
American archaeology, though, is changing fast. There are untold
mysteries about the first Americans; facts are still buried underground
and underwater. “We’re never arguing from complete knowledge,” says
Brad Lepper of the Ohio Historical Society. “Whenever someone reports
‘the oldest date site in Siberia,’ you can bet that within a decade,
another site will be found that’s earlier.”
A scientific consensus, moreover, can be mistaken, Goodyear points out.
Not long ago, scholars supported the Clovis-first orthodoxy, which many
now say was dead wrong.
“The Western Hemisphere is a vast place,” says Goodyear, “and to think
that human beings, as clever as they are, with the technologies they
knew how to create, couldn’t somehow leak into this hemisphere
(thousands of years before Clovis) seems the height of hubris to me
now. You have to leave all of these hypotheses on the table. It’s not
good enough anymore to say, ‘That’s impossible.’ We have to leave our
minds open.”
One hypothesis about the first Americans, though, is gaining
particularly strong support. The first explorers of the Americas
followed shorelines to arrive here. Tens of thousands of years ago,
people in East Asia were already living off the resources of the
littoral edge. And some hunter-gatherers were heading across open water
in small vessels, rowing into the unknown. Near the beginnings of
modern human history, we were already a coastal species, drawn to the
sea.
__________
Sidebars: COASTS INSPIRE MODERN HUMANITY
The first flowering of modern intelligence might have been stimulated
along the edge of the ocean by our ancestors’ use of coastal resources.
Our distant ancestors evolved on Earth for about seven million years,
over which time some 20 different known hominid species thrived and
then disappeared. All are extinct now but one—our species, Homo sapiens.
Homo sapiens—anatomically modern people who look like us—evolved in
Africa perhaps as early as 160,000 years ago. Although modern-style
humans were physically less robust than any of their predecessors,
early Homo sapiens were blessed with the large brain that we have today.
Even so, early anatomically modern humans lacked our capacity for
complex thought. They continued to use relatively primitive stone tools
for thousands of years.
But about 80,000 to 50,000 years ago Homo sapiens began a remarkably rapid intellectual transformation.
During this period people began fashioning more sophisticated
tools—buttons, needles, and harpoons—from a variety of materials:
ivory, antler, and shell. They also started creating art in the form of
carvings, engravings, ornaments, and cave paintings; keeping records on
bone and stone plaques; making music on wind instruments; and
organizing increasingly complex hunting and fishing practices.
This burst of creativity is what we associate today with modern human intelligence and behavior.
What stimulated the human mind? William H. Calvin, a neurobiologist at
the University of Washington, argues that a new mental operating system
abruptly appeared in humans—a “software upgrade” that enhanced our
ancestors’ ability to anticipate and plan.
Did this revolution result from a genetically based change in the
wiring of our brains? Or did it emerge from cultural adaptation—the
innate creativity of humans flowering to a higher potential? Or both?
When humans experienced this burst of creativity, they also probably
began creating complex sentences that made sense to other humans.
People developed language syntax—the logical patterns within strings of
words—to communicate. Such innovations allowed our ancestors to play
games that had intricate rules, to break down and understand how things
work, and to experiment and pass on what they had learned through
stories and intergenerational lessons.
Researchers point to two behaviors that especially indicate modern
behavior and both involve art forms: people intentionally drawing or
carving images on cave walls or other materials; and people using
ornaments such as beads.
Art is interwoven with higher language skills. Humans need complex
language to share cultural meaning of beadworks and etchings. The first
behaviorally modern humans, Calvin writes, began to show the “cognitive
ability to reduce the world around them to symbols expressed in words
and art.”
So when did these symbols first occur? The oldest documented modern
human behavior has been found in a cave on the southern Cape shore of
the Indian Ocean in South Africa. In Blombos Cave, archaeologists
excavated sophisticated hunting and fishing tools, necklace beads, and
engraved ochre pieces, dating from about 75,000 years ago, according to
studies by archaeologist Christopher S. Henshilwood and his colleagues.
About 80,000 years ago, the world was growing much colder as the ice
age accelerated to a deep freeze. In East Africa, the changing climate
made water and prey scarcer; savannah was turning to steppe and desert.
Some populations began moving to ribbons of coast where they could
exploit food resources from the sea but also hunt land animals nearby.
The southern Cape about 75,000 years ago had a moderate climate and more consistently available resources than inland areas.
Archaeologists suggest that inland people migrating to the coast
competed for resources with people already living there. Both
populations could have created more complex social relations to share
those resources, which spawned the world’s first known art forms.
Temperate weather and a more diverse food supply near the sea in a time
of rapid climate change could have encouraged cooperation among various
populations, which pushed Homo sapiens on the path to modern human
consciousness.Our ancient ancestors coped with dramatic climate
fluctuations, but now for the first time humans are contributing
significantly to global climate change, which could cause a violent,
abrupt climate disruption.
Over hundreds of thousands of years, intense cold periods called
glacials—popularly known as ice ages—have been interspersed with
briefer, much warmer periods called interglacials. Glacial ages usually
last about 90,000 years followed by interglacials that average about
10,000 years. Some warm periods last 5,000 years, others 20,000.
The Earth’s natural state is very cold; its most common age is ice. But
even the last glacial age was not uniformly cold; there were many
extreme, sudden temperature changes.
The current interglacial has lasted about 12,000 years, and it has been
an unusually stable period of warmth. Eventually the Earth will cool
down again into another ice age.
Changes in the Earth’s orbit trigger abrupt but long-term shifts in
climate. Wobbles in the Earth’s orbit alter the amount and distribution
of solar radiation on the planet’s surface, which strongly reshapes
atmospheric and ocean currents. Such currents are great movers of heat
around the world, particularly from the equator to the temperate
regions. When these currents are altered, the Earth can turn much
warmer or much colder.
Such natural disruptions have altered global climate many times in the
geological record, sending the planet from warm-and-wet periods to very
cold-and-dry periods. Extreme changes in global climate have occurred
over periods as brief as 20 to 50 years.
Today’s problem, many scientists say, is that no one knows whether
human activities—such as burning fossil fuels—could set off a similar
chain reaction in the Earth’s climate, spawning another extreme swing
in global temperature.____________________
Reading
and Web sites: Adovasio, J.M. with Jake Page. The First Americans: In Pursuit of Archaeology’s Greatest Mystery. New York: Random House, 2002.
Blombos Cave Project. www.svf.uib.no/sfu/blombos/The Site.html
Center for the Study of the First Americans www.centerfirstamericans.com
Climate Timeline Information Tool www.ngdc.noaa.gov/paleo/ctl/index.html
Calvin, William H. A Brief History of the Mind: From Apes to Intellect and Beyond. Oxford: Oxford University Press, 2004.
Dillehay, Thomas D. The Settlement of the Americas: A New Prehistory. New York: Basic Books, 2000.
Fagan, Brian M. The Great Journey: The Peopling of Ancient America.
(Updated Edition). Gainesville: University Press of Florida, 2003.
Jablonski, Nina, Ed. The First Americans: The Pleistocene Colonization
of the New World. San Francisco: California Academy of Sciences, 2002.
Madsen, D.B., Ed. Entering America: Northeast Asia and Beringia Before
the Last Glacial Maximum. Salt Lake City: University of Utah Press,
2004.
NOAA Paleoclimatology Program www.ncdc.noaa.gov/paleo/primer_history.html
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