The Mathematical Significance of the Effigy Mounds of the Mississippi River Valley

    For centuries humans have marveled over the monuments built by peoples of the past.  The Pyramids in Egypt, the Pyramids of the Aztec and the Maya in Central America, including the cliff dwellings of the Anasazi in the Southwest of North America are all fascinating to us. And now with the great earthen mounds that are in the Northeast and Midwest of North America.  Why were these structures built and what might they have been used for?  Since their discovery by Europeans at the time of colonization of North American there has been much speculation as to what these mounds were.  Through this paper I hope to give some insight into these mounds and their significance in showing just how sophisticated the Natives of North America were at the time of the mounds’ construction. This being a Mathematics course the ideas that I will be talking about will deal with the possible mathematical reasons for the construction of the mounds in the first place.  The main two reasons for building the mounds I believe to be first they were used for burial mounds/markers and second for astronomical purposes marking the suns cycles and certain astronomical events and the cycles of stars.

    Of these two uses I’d like to talk about the former first.  Even though this is a Math paper I feel it is important
to make one aware that these mounds weren’t just for show but that there was some significance behind their construction.  Of the mounds that were used as burial sites there were several types.  There were effigy mounds, mounds that were built in the shape of something usually an animal, and conical mounds used.  The conical mounds may have signified a single star and because these were usually burial mounds they could represent a star that was present in the sky at the time of the deaths of those buried in them (Aveni 224).  The mounds found in Mound City (Fig. 1) are a good example of the use of conical mounds for burial.  Not all of the conical mounds represent single stars; there are some that may represent groups of stars.  Along this same line of thinking those mounds that were built in effigy and used as burials could represent a particular clan that those within belonged to or they represent a spirit or totem animal for those inside.  Without actually having been there at the time of these mounds construction all we can do is speculate as to what their true meaning is.

    Until just recently the idea of the mounds meaning anything at all other than that they were used for burial wasn’t even thought of.  Arlow B. Stout wrote a paper in the early part of the 1900s entitled Effigy Mounds and Mosaics in the Valley of the Mississippi.  This paper described several of the earthwork mounds that were found in Wisconsin.  He makes an observation about the placement of the mounds saying, “In the arrangement of the mounds constituting a group no uniform plan was followed.  The mounds seem to be grouped to suit the natural topography although there is a tendency for large groups to be strung out in rows.”  It is possible that these mounds represent star clusters or some other astronomical body.
 

    I would now like to talk about the other use for the mounds and that is their astronomical significance.  There were three distinct mound-building epochs each being attributed to a different group of people, by time frame and the style of the structures.  The first of these epochs was the Poverty Point culture that emerged during the Late Archaic Period in the Lower Mississippi Valley.  The Poverty Point site that was this culture’s major center was occupied from about 1500 to 700 BC.

    This site is interesting because it is distinguished by a set of earthen embankments that form six concentric semicircles each about six feet high (Fig 2).  The open end of the semicircles faces east. The distance from the northern tip to the southern tip is about 1,200 meters, or about three-quarters of a mile.  The width and the distances between the embankments are relatively the same at some 50 to 150 feet.  In the open area of the semicircles is a 37-acre plaza that opens up into surrounding Mississippi swamp/flood plane.  There are four aisles cut into the embankments and they may have been used as a solar calendar because two of the aisles point north and south, one marks the sun’s rays at sunset on the summer solstice, and one marks the sun’s rays for the winter solstice (Shaffer 29).

    Also at this site are the remains of a large bird mound.  Some of it has been damaged over time from farmers plowing the top to a construction crew using some of the dirt from its tail for the substructure of a nearby highway.  The mound used to stand seventy feet high.  This bird faces west and it’s wings spread on a north-south axes with a span of 640 feet.  It was once 710 feet long from beak to tail tip (Shaffer 29).  It is not known what this effigy bird’s purpose was but I believe that it may have been a way to represent the sun.  Because the sun moves from East to West and the opening to the embankment’s faces east and the bird faces west it could be reasonable to believe that the bird is the sun traveling though the sky to the west.  It’s size alone could be an indication to how big it needed to be in order to represent the sun by the people who built it.

    The next mound building epoch was that of the Adena-Hopewell culture around 500 BC to 400 AD.  This culture has many mounds that can be found in Ohio.  Of all the mounds built by these people at this time the one that stands out the most is that of the Great Serpent Mound (Fig. 3) found in Adam’s County Ohio.

This mound is by far one of the most famous.  Of the entire serpent like mounds throughout the world the Great Serpent Mound in Ohio is the largest.  The distance from the snake’s head to its tail is about 800 feet, but if it were to be stretched out it would be about 1,300 feet long.  Due to erosion and plowing it only stands about 4 feet off the ground and has a width of about 20 feet (Shaffer 40).  The snake’s mouth is wide open and looks like it is about to swallow an egg.  There is some speculation as to what this egg shape represents.

    One speculation is that the egg is the sun because there is a Native American legend that says the sun was once swallowed by a snake.  Another possibility is that the snake represents Ursa Minor and the egg represents the moon.  If this is the case then we can see the snake’s tail being anchored by Polaris.  The curve in the snake would then be congruent with the curve in the “handle” of Ursa Minor and the head may be the “dipper”.  The coils in the snake’s tail may represent Ursa Minor’s movement around Polaris.  A possible explanation of the egg representing the moon is from an oriental legend of a serpent swallowing the moon associated with lunar eclipses.  Dr. Elizabeth Baity who is an expert in Asian proto-history suggests this possibility (Aveni 229).  If this is true than maybe the snake mound represents a lunar eclipse that occurred after Ursa Minor made three rotations around Polaris.  A date for this event can’t be pointed out, but perhaps that knowing the mound was from the Adena period we can in effect count backwards to see if such an event took place.

    Another culture that appeared during this epoch was that of the Hopewell.  These people formed their culture in the valley of the Scioto River in Ohio and along two other Ohio tributaries around 300 BC.  The Adena and Hopewell cultures existed side by side and it is believed that the Hopewell formed from within the Adena culture.

    A notable structure for these people that I have found is that of the East Fork works (Fig. 4) in Ohio. These earthworks lay along the east fork of the Little Miami River, about 20 miles above its mouth near Milford, and about 25-30 miles east of Cincinnati.  Of the mounds in this area one set stands out because of its uncanny resemblance to the Jewish Hanukkiah.  Inside the structures walls it looks like the nine-branched candelabrum for the Jewish festival of Hanukkah.  And at the top of the structure it looks like a oil lamp.  The base and left side walls were once each 2000 feet long.  However, they have long since been plowed level and their orientation and exact location are unknown.  This site is interesting because of its use of geometrical shapes in its design.  Unlike the other mound sites I’ve looked at these don’t seem to lend themselves to the alignment of starts, but perhaps their creators attributed them to the something equally important.

    The third and final mound building epoch took place from about 700 AD to 1731 and is called the Mississippian period.  The major culture area of this time was at a site named Cahokia at Collinsville Illinois.  This site was the preeminent center in the Eastern North America.  The largest and perhaps the most powerful north of Mexico (Fig. 5).
 
 

The 100-foot mound at the center of the site is the world’s largest earthwork and the third largest structure of any kind in the Western Hemisphere in 1492.
 
 

The center platform mound is in the center of a diamond-shaped site that covers about 2,000 acres (Fig. 6).

This mound faces south and looks out over a large plaza.  Enclosing the palace mound, the plaza and some sixteen other mounds was a wooden palisade with a circumference of two miles and at every 70 feet was a watchtower.  The palace mound was situated within the palisade so that its back was along its north wall and its front faced south.  This was done so that the palace mound would be hit by sunlight all day and all of the shadows would have been sent to its rear.  At each of the diamonds points there was a mound depicting each of the cardinal directions, North, South, East, and West.  At about 1,000 yards to the west of the platform mound and about 750 yards outside the palisade was a structure that is now referred to as the “American Woodhenge.”  This structure is a precise circle about 410 feet in diameter and made up of 48 large posts.

    At each of the cardinal directions a post was positioned and the others were evenly spaced between them forming a complete circle.  This structure lends itself to be a type of solar calendar allowing those that supervised it to anticipate the coming of the solstices and the equinoxes as well as other important dates (Shaffer 53-4).

    I did not find any other evidence of astral events depicted in the mounds at this site.  But it is possible that over time they have eroded because it is estimated that there may have been 120 mounds in this one area alone.

    Through my research I have discovered civilizations in North American that had great knowledge of the stars and the movement of the sun.  And through their unique perspective of these heavenly bodies they depicted them in tangible physical reality for all those in their society to experience and take part in.  It is very evident that these people were watching the sky and to them it was important, either they were looking for new gods or they felt that what ever it was that they were watching was important and it needed to be documented.  With the help of the mounds they left behind we can get a better understanding of who these people were and how they lived their lives.  The fact that they used the shapes of animals to depict some of what they saw also tells us that they had a much closer connection to the environment around them than those in Europe and it helped them explain what it was they were seeing.

Aveni, Anthony F. Archaeoastronomy in Pre-Columbian America.  University of Texas Press, Austin and
    London, 1975.

McCulloch, J. Huston.  Ohio’s East Fork or “Hanukkiah” Earthworks. 1998.
    http://www.econ.ohio-state.edu/jhm/arch/efw.html

Shaffer, Lynda Norene. Native Americans Before 1492: The Moundbuilding Centers of the Eastern
    Woodlands.  M.E. Sharpe, Inc. Armonk, New York; London, England, 1992.

Shambaugh, Benjamin F. Proceedings of the Mississippi Valley Historical Association from the Year
    1909-1910 Volume III. The Torch Press, Cedar Rapids, Iowa, 1911.

Silverberg, Robert. Mound Builders of Ancient America: The Archaeology of a Myth. New York Graphic Society,
    LTD, Greenwich, Connecticut, 1968.