Abstract
Building convincing arguments in archaeoastronomy is not about
whimsical map work or developing arcane numeracies. Contextual
cultural syntheses are paramount. Careful mathematical modeling,
cultural archaeology, paleobotany, comparative ethnology, concepts
involving monumental architecture, and calendar histories are
examples of the topics woven into any perspicacious overview.
This poster demonstrates both winter and summer solstice rise
events at a Hopewell geometric enclosure, development of these
monuments from earlier Adena forms, as well as similar sightlines
at other Hopewell sites. The intensification of agriculture (c.200BC)
in the Eastern Woodlands was synchronous with the creation of
the Hopewell earthwork calendars.
"Mystical" popularization and poor scientific method plague archaeoastronomy. Historians, archaeologists and astronomers are often skeptical of interdisciplinary claims that draw upon their specialties. For these reasons, any proffered hypotheses must be doubly rigorous.
During the past twenty years greater attention has been paid to the grand earthworks of the upper Ohio Valley. In that time, various researchers have penned papers of varying veracity. The ancient mounds of the eastern US and especially those in Ohio have challenged the academic community for over 150 years. These monuments, remnants of the Hopewell culture, represent the apex of the mound building traditions that had their start in Louisiana some 5400 years ago. The vast majority of mounds in the US have an obvious utilitarian function (mortuary, defensive, etc.). The Hopewell enclosures of Ohio are by contrast anomalous.
Though preceded for about 400 years by circular enclosures created by the Adena culture, the geometric earthworks built by the Hopewell were three to four times as large and included lengthy parallel embankments, squares and octagons. As early as 1820 Atwater speculated that these groups might have a calendrical or astronomical underpinning. Subsequent interpretations focused on a ritualistic function, though lacking in specificity. Today, the archaeoastronomer analyzing Hopewell enclosures must contend with various prejudices and prevailing models. Overall, it will be the repeated demonstrability of calendrical sightlines at all such studied groups that will constitute a convincing argument. So far, all such analyzed sites have revealed solar and/or lunar indices. The poster presented here focuses on the Hopeton Earthworks, a Hopewell geometric enclosure in Chillicothe, Ohio, and more briefly on the Fairground Circle in Newark , Ohio.
Other Ohio Hopewell mound sites not mentioned here have been convincingly interpreted and add to the corpus of data. [1]
The Hopeton Earthworks
The Hopeton site is rather typical of the class of earthworks referred to as Hopewell geometric enclosures. These are earthworks usually composed of two or more conjoined polygonal or circular embankments on the order of 1000 feet or more across. In 1983, I analyzed Hopeton per possible calendrical sightlines between its various "gateways". In doing so, I considered the factors of refraction, latitude, horizon elevation, etc. Hopeton is replete with both lunar and solar indices. In addition, the eastern horizon as seen from Hopeton is formed by a mountain range that affords many gaps and peaks that act as alignment foresights. The presence on this range of burned stone piles at these foresight loci further lends credence to the calendrical interpretation.
Because the lunar indices can only be tested every 18.6 years, and with greater difficulty than the solar events, and in the interest of brevity, only the solstice rise events are shown for Hopeton. Nonetheless, these are highly notable. The summer rise event just catches the northern end of the aforementioned mountain range. Had the site been placed further north, the use of this landform to index summer solstice would have been lost entirely. Of greater interest is the winter solstice. This alignment utilizes the longest possible sightline in the polygon, and it is centered on a discrete gap in the mountain range. Both of these horizon foresights have scattered fire-cracked rock (FCR) concentrations at or near them. Hopeton recently had reliable radiocarbon determinations made per its construction date: this was found to be in the first century AD, early in the lineage of Hopewell enclosures. I believe this is reflected in the relative irregularity of Hopeton: other Hopewell sites have highly regular square shapes, whereas here we find an irregular polygon.
A large boulder just northeast of Hopeton hosts a possible linear petroglyph. This rock is in exact line with the summer solstice rise sightline, and may represent an early effort at marking the event. The nature of this feature has yet to be confirmed by a petroglyph expert, and is probativley noted.
Adena Circles
Adena refers to the culture that preceded the Hopewell in the same Ohio Valley area. The current interpretation holds that Adena was an earlier phase of regional development, though some hold they were an entirely different people. Whichever is true, it is certain that both groups manifested similar mortuary and artistic styles, and that they shared places in the mound-building continuum. The earliest known Adena circle, the Dominion site, was located in present day Columbus, Ohio. It was constructed no later than 500 BC. Like the subsequent Mt. Horeb site in Kentucky and the Anderson site in Indiana, this circle featured a ditch interior to the circular embankment. Many hosted a sub-mound circular postmold pattern indicative of a familiarity with geometrical morphology. These structures were probably associated with mortuary uses, but their frequent ridgetop locations have been interpreted as possibly related to horizon monitoring of sunrises. [2]
The presence of an interior ditch is seldom found in the subsequent Hopewell enclosures. Notably though, one large circle has such a ditch. Recent radiocarbon dating determined that the Fairground Circle was built no earlier than 160 BC. This is possibly the first of the twentyor-so Hopewell geometric enclosures that existed in Ohio. It is this ditch, combined with the presence of a singular gateway, that is the best link suggesting that these Hopewell forms developed out of earlier Adena shapes.
The Fairground Circle
This beautiful monument is the best preserved of the Ohio Hopewell geometric enclosures. As I demonstrated in 1982, this circle's singular gateway indexes the May cross-quarter sunrise (Mayday or Beltane). Though such calendrical divisions are not ubiquitous worldwide, the cross-quarter dates were monitored by as diverse cultures as Celtic Britain and the historical Hopi.
Back in 1982, data on foodstuffs, especially that of plant foods, was notably lacking in Hopewell archaeology. Water floatation and a keener interest in this information has led to a burgeoning of such data. It is increasingly accepted that Eastern North America was an independent center for the domestication of various plant foods. This suite of plants is known collectively as the Eastern Agricultural Complex. [3] Domestication of some of the species involved occurred regionally as early as 2000 BC. The widespread use of these produced plant foods, in volumes sufficient to be considered a staple, did not occur till circa 200 BC. This is synchronous with the initial creation of the Hopewell geometric earthworks, specifically the Fairground Circle, and later Hopeton. (These two sites are geometrically rather unsophisticated, compared to other Hopewell groups. There we find accurate squares and even octagons. This further suggests that Fairground and Hopeton were the progenitors of later more complex Hopewell groups.)
The Eastern Agricultural Complex
The marking of such an agriculturally salient date as the May cross-quarter event underscores the nature of Hopewell seasonal monitoring: subsistence scheduling. But why in Ohio? The archaeological record suggests that the foods of the Eastern Agricultural Complex (EAC) were not raised there till circa 200 BC. These plant foods had been cultivated more than 1500 years earlier in parts of Arkansas and Illinois. Yet there we find no monumental architecture evidencing the use of horizon calendars. So, why in Ohio?
The answer, I believe, was the climate. Ohio hosted reliable flint sources, and contained land fecund with tillable soil, yet it was notably cooler than the other EAC use areas. More exactly, the springtime weather was more capricious. Archaeologists have noted that agriculturally marginal lands became host to monumental earthwork architecture (e.g. Britain and Western Europe) and historically noted horizon monitoring (e.g. Hopi area). Interestingly, the Hopi called the month preceding May Day hakiton-muya, "the waiting month". Even though warm weather would occur prior to May Day, hard freezes could occur still. It was more prudent to wait till the safe frost-free interval whose beginning was marked by the May cross-quarter date.
I analyzed modern weather records for five cities in the area of prehistoric EAC use. There is no convincing data that the climate patterns were grossly different 2000 years ago from those of today. My analysis revealed that Ohio indeed experiences later frosts and probably more importantly a greater range in temperature extremes in the springtime. Also notable is this: Hopewell habitation sites in Michigan, further north than Ohio, show no reliance on the EAC cultvars as foodstuffs. So even though the artforms and mortuary customs indicative of Hopewell existed in Michigan during the Middle Woodland period, the Michigan Hopewell were not farmers.
Conclusions
Earth was a ubiquitous building material for Native Americans in the eastern US. It is not surprising that forms of monumental architecture, originating with mortuary edifices, would be developed to mark horizon calendar sightlines. There is an increasingly clear continuum of mound-building practices noted in the American archaeological record. The origin and development of Adena circles sensibly precedes the grand Hopewell enclosures. Though not all archaeologists are convinced (as if this could ever happen!), it is also becoming clear that Native Americans of the Midwest and Upper South were horticulturists, and eventually agriculturists, beginning about 4000 years ago. The hunter-gatherer lifeways of collecting foods was gradually augmented by producing foods.
Based on mound structure morphology and radiocarbon dates,
it appears that the Fairground Circle and Hopeton were the two
earliest constructed of the Hopewell geometric enclosures. Both
of these sites mark the May cross-quarter sightline, and Hopeton
many more. The indexing of this agriculturally important date
underscores the importance of farming to the Hopewell. The creation
of these two monuments was contemporary with the emergence of
the use of the EAC cultivars in the Ohio area.
Both of these sites have sightlines that are keyed to extant topographical
features along their respective horizons. FCR concentrations have
been noted at some of these horizon foresight areas.
More work needs to be done. Unfortunately, most of the Hopewell enclosures have been destroyed. Survey data from the 1880s is the most accurate information per their original design, but many were never surveyed. Researchers must be held to the highest standards, lest the entire field of study is undermined.
[1] Three other Hopewell enclosures have been reliably analyzed: the Newark Octagon , Hively and Horn (1982); the High Bank earthworks, Hively and Horn(1984); and the Liberty earthworks, Turner (n.d.2). All contain solar and/or lunar sightlines. Articles by William Romain on Hopewell archaeoastronomy are classic examples of how not to undertake archaeoastronomical analyses. For a review of Romain's efforts, see James Marshall's 1999 article "A Rebuttal to Archaeoastronomers: Science Begins with the Facts", Ohio Archaeologist 49(1):32-49.
[2] See Berle Clay's 1986 article "Adena Ritual Spaces"
in Early Woodland Archaeology, edited by
Kenneth Farnsworth and Thomas Emerson, pp. 581-595. Kampsville
Seminars in Archaeology, Volume 2. Center for American Archaeology,
Kampsville, Illinois.
[3] The following seven species make up the plants known collectively
as the Eastern Agricultural Complex: squash (Cucurbita pepo
var. texana); a domesticated form of marshelder, (Iva
annua var. macrocarpa); erect knotweed (Polygonum
erectum); maygrass (Phalaris caroliniana); a domesticated
form of lambsquarter (Chenopodium berlandieri ssp. Jonesianum);
sunflower (Helianthus annuus); and little barley (Hordeum
pusillum).