Mounds are artificially constructed heaps or banks of earth built to contain sacred objects. Their basic construction is the same all over the world: a pit is dug and lined, and the sacred contents are deposited and covered with earth. Sometimes these objects are sprinkled with red ocher, a pigment used to make paint, perhaps as a way to revive the spirits thought to dwell within them.
If we were to go for a walk on an open plain in Illinois or Ohio and were to come across one of these “dirt piles,” we probably would ignore it. But an archaeologist would be thrilled to find a sacred mound, for it might conceal vital clues to the ancient past of Native America: human and animal bones, weapons, ornaments, and mysterious clay figurines.
Some of the oldest and largest mounds in the world are found in America. The older North American mounds are cone-shaped and can reach heights of 70 feet (21 m) or more. Some of the more recent mounds are shaped like animals, people, or abstract forms and are therefore known as “effigy” mounds because they symbolize another object. No one knows what the effigy mounds were used for. Some archaeologists believe that they functioned as totem poles. As with totems, a few human bones were buried within the effigy mounds for their symbolic value. Found mostly in Wisconsin, Minnesota, Iowa, and Illinois, effigy mounds are shaped like deer, turtles, snakes, eagles, foxes, bears, birds, and human beings. Today, the Great Serpent Mound winds along a river near a public park in Peebles, Ohio, for a distance of over 1 mile (1.6 km), its head recoiling as if to snatch into its hungry jaws a frog or other mysterious oval-shaped object. An enormous bird mound at Poverty Point, Louisiana, faces westward, its wings outstretched in a symbolic moment of flight.
Tens of thousands of mounds are found in the United States. Many more originally must have existed. St. Louis was the location of so many sacred mounds that it was once known as Mound City; today just one of those mounds remains. A great number of mounds have been bulldozed into the ground, their contents either thoughtlessly pirated by treasure hunters or casually destroyed.
Most mounds were used for burials, but a significant number, built in the vicinity of the Mississippi River about AD 700 and later, were known as Temple Mounds. They looked like flat-topped pyramids crowned with wooden temples.
Who built the North American mounds? Archaeologists believe that they were the product of two ancient native cultures: the Adena and the Hopewell.
The Adena people probably were descended from archaic native Americans who inhabited parts of America in 3000 BC. Found primarily near Chillicothe, Ohio, but also located throughout north Kentucky, West Virginia, Indiana, and Pennsylvania, the Adena built conical mounds averaging 10-20 feet (3-6 m) in height. In the simplest form of Adena burial, the body was placed in a shallow pit lined with clay or bark and covered with layers of different-colored soils. As time went on, the Adena returned to the same burial mounds, added more burials on top of them, and covered them with fresh soil. This process went on for several generations until the mounds got to be enormous, some reaching heights of over 50 feet (15 m).
Some of the higher-ranking members of Adena society were given special burials. Their bodies were wrapped in cloth, sprinkled with red ocher, and placed in specially constructed thatch houses. Sometimes the burials were accompanied by grave goods—personal possessions such as weapons and tools, left there for use in the afterlife. The houses were then burned, and mounds were constructed over the charred remains.
Probably descended from the Adena tradition, the Hopewell culture originated in southern Illinois. Major Hopewell settlements are also found in Ohio, as well as New York, Ontario, Louisiana, Mississippi, Alabama, Tennessee, Georgia, and Florida.
Like Adena mounds, Hopewell mounds are conical, but some are also dome-shaped. They average 20-30 feet (6-9 m) high and are often found in clusters enclosed by artificially constructed ridges that may be circular, square, or octagonal. Mounds often were part of large social and religious complexes built on elevated areas, usually near a river valley. Because of their enormous size, their construction often required hundreds of workers, who laboriously scooped the earth with clamshell hoes and large animal bones and then carried it back to the mound in baskets and skin aprons. Many of these workers may have been women.
Most Hopewell were cremated, with burial usually reserved for higher-ranking members of society. When it came time for the funeral ceremony, the body was clothed in colorful garments covered with pearls, bear-teeth buttons, and other ornaments. Around the body were placed elaborate grave goods: cups made from giant sea snails; platform pipes decorated with birds of prey, beavers, cougars, toads, or bears; geometric or animal shapes carved out of mica (a silicon-containing mineral that divides into thin, partially transparent layers); panpipes; weapons; and many other objects. Wood carvings were deliberately broken, perhaps as a form of ceremonial sacrifice. Members of the deceased’s family may also have been ritually sacrificed and buried at his side, to accompany him on his journey to the next world.
The Hopewell also continued the practice of placing bones in mortuaries known as charnel houses, some extending for more than 200 feet (61 m) and containing individual compartments. The houses were then burned, and a mound was constructed over the remains.
Flat-topped pyramidal temple mounds are found in southern Mississippi, as well as Georgia, Oklahoma, Wisconsin, and probably beyond. Reaching 70-80 feet (21-24 m) in height, they were built in clusters, often around a central plaza. Many of them have log stairways or ramps leading up the sides to the temple, which was constructed of mud and thatch and may have housed an eternal flame.
The most famous temple mound complex is the Cahokia Mound site in southern Illinois. Covering more than 16 acres (6.4 ha), Cahokia Mound is larger than the largest pyramid in Egypt. It contains as many as 67 mounds. Monk’s Mound, the largest of these at more than 50 feet (15 m) high, was the site of the temple that was probably occupied by the ruling family. Its construction may have required more than 300 years of labor and more than 22 million cubic feet of earth.
Also at the Cahokia site is a mysterious structure known as Woodhenge. Similar to Stonehenge in construction, it consisted of a circle of red cedar posts that may have been used as a solar calendar by the priests to mark off specific astronomical events. These would have included the two annual equinoxes and the winter and summer solstices. The equinox is the point at which the center of the sun crosses the celestial equator and day and night are of equal length. The solstice is the point at which the sun is at its greatest distance form the celestial equator and appears to be farthest north or south in the sky. Knowledge of these events helped the priests to determine when to plant crops.
High-ranking members of society continued to be buried in the temple mounds with an elaborate accompaniment of grave goods, including a copper mask of the “long-nosed God,” similar to that made by the ancient Maya. Most people, however, were buried in cemeteries outside the cities.
After 1400, mound building in North America came to a mysterious end. Flood, famine, or disease may have swept through the Native communities, claiming the lives of many of the mound builders. A widely accepted explanation holds that the decline in mound building was a reaction against a terrifying religious revival known as the Southern Death Cult. Its obsession with death is displayed in horrifying grave goods, including weeping masks, and skulls engraved with spiders, centipedes, and frightening figures that are a combination of humans, animals, and serpents.
Objects are removed from a mound in a systematic process of mapping and retrieval known as excavation. To begin excavating a mound, an archaeologist may dig a trench around the periphery and proceed to dig in pie-wedged sections, exposing each successive layer of burial. The area is sketched and photographed, and the location of each individual object recorded. Skeletal remains are examined for position (for example, extended or flexed) and for the direction of the burial along the cardinal points (north, south, east, or west).
After removal from the mound, objects are assigned a date according to one of several procedures,
Carbon-14 —A radioactive isotope of carbon that decays at a uniform rate in living matter, used to determine the age of archaeological finds.
Charnel house —A building where dead bodies or bones are kept.
Effigy mound —A mound constructed to represent a living being or an abstract shape.
Excavation —The step-by-step removal of buried objects at an archaeological site.
Grave goods —Personal possessions, such as weapons and tools, buried with the deceased for use in the afterlife.
the most common of which is carbon-14 dating. Carbon-14 (or radiocarbon) is a radioactive isotope that is present in the atmosphere and absorbed into the tissues and bones of all living things. After death, carbon-14 is no longer absorbed but begins to decay to nitrogen at a fixed rate, or half-life, of approximately 5,730 years. Because carbon-14 decays at this fixed rate, an estimate of the age of an object can be made based on the rate of decay of its radiocarbon.
New methods of excavation are being developed to avoid disturbing the underground contents of mounds. At the Cahokia site, researchers at the University of Southern Illinois at Edwardsville are using subsoil remote sensors. Linked to above-ground computers, the sensors relay electrical readings that determine the composition of the underground objects on the basis of their electrical properties.
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