Thursday, June 11, 2009

The Mystery of Zimbabwe’s Spherical Rock-holes

Who made the spherical holes? Voytek never did discover and up to the day of his tragic and horriffic murder he was still searching for an explaination.

Could it have been UFO's - Voytek and Dorothy thought not - but who knows?

This is the article that appeared in the Pre-History Society’s Newsletter, June 2004

The Mystery of Zimbabwe’s Spherical Rock-holes

By Voytek and Dorothy Popiel

For the last ten years we have been researching the existence of spherical rock-holes in Zimbabwe. This article is a brief account of some of our findings and thoughts on the subject.

Whilst there are probably hundreds of thousands of grinding hollows in granite sites throughout Zimbabwe, the ones we are studying are in a class of their own: uncannily circular both in plan and cross-section making them spherical or, if you prefer, hemi-spherical. It is this feature and the precision of the hollows that has caught our interest.

Generations ago someone, using simple technology such as a rubbing stone, manually hollowed out an almost perfect hemi-sphere in rock. The mystery is ‘why are the hollows so precise and spherical’.

The accuracy of the hollows suggests the use of a machine, yet at the time they were made (before the arrival of Europeans in Zimbabwe) the wheel was apparently unknown in this part of the world.

The Shapes of Grinding Hollows
The existence of a large number of man-made rock holes in Zimbabwe is well documented in archaeological and other publications. It is accepted that these rock-holes were created by the indigenous people when milling food­stuffs, such as small grains, or mineral ores, in partic­ular gold bearing ores. Maize came later and, because of the larger pip size, wooden pestles and mortars proved to be more efficient for grinding it.

Whatever was milled, it was effectively done with a pestle and mortar where the pestle is a small rock or a wooden pole held in one or both hands, and the mortar is a portable flat rock, the surface of a flat boulder, or massive granite hill.

Analysis of the shapes can suggest the human activity and the milling process. To date, two main types of rock holes are generally referred to: circular and elliptical, variously described as ‘mortar stones’, ‘circular grinding hollows’, ‘elliptical grinding hollows’, ‘quern stones’ and ‘dolly holes’.
To do justice to the various shapes and grinding methods, however, and relate the hollows to the activity, i.e. mining or domestic use, we have classified them as:

Use – Features
Circular, elliptical or oval, guyo
grinding foodstuffs, shallow
rubbing in circular motion or backwards/forwards
Circular, dolly-holes
grinding minerals, deep, rounded rim
percussion or pounding
Narrow and groove-like
grinding minerals, shallow, long and narrow
rubbing lengthways with a narrow stone
Spherical, circular in plan and cross-section
Most likely grinding foodstuffs, deeper than a), shallower than b), sharp rim, with chamfer and cusp
Under investigation. Probably rubbing in a circular motion in 2 planes to produce a spherical shape

The shapes of holes vary both in plan and cross-section. Some are elliptical and shallow (a), whilst others are circular and deep (b). A third type (c) is long and very narrow, with the depth approximately equal to the width: we understand this type was used exclusively for grinding minerals. The fourth type (d), the one we are researching, is spherical, i.e. circular in both plan and cross-section with, generally, a sharp rim.

The elliptical grinding-hollows (a) are known in Shona as ‘guyo’ (singular) or ‘makuyo’ (plural), and were used mainly for grinding foodstuffs (and still are in some rural areas). Archae­ol­ogists often refer to the circular and deeper holes as ‘dolly holes’ (b), a term used in the mining industry. Percussion-type dolly holes tend to be deeper than they are wide and the edges of such holes are rounded and not as neat and sharp as the edges of the rock-holes we are considering.

The size and motion of the rubbing-stone or pestle determines the shape of the mortar, i.e. the hole or hollow. One formed by rubbing a stone backwards and forwards would create an elongated or elliptical and relatively shallow hole [type (a) and type (c)], whereas one formed by a pounding motion using an upright pestle – whether a stone or a wooden pole – would create a deeper, circular, depression [type (b)] with a rounded rim.

We assume the method of producing type (d), our spherical rock-holes, was by a stone tool driven and guided by hand in a circular and rocking motion. Because of the geometry and the precision achieved, the method used is the most fascinating part of this mystery.

Simply rubbing a stone on stone in a circular motion by hand would not produce what we are now looking at. Yes, it could look roughly circular in plan and cross-section, but would deviate from a true circle because the inaccuracy of the hand motion, the variation of the pressure applied as the stone is guided, and the nature of the base rock (e.g. hard and soft spots) mitigate against producing a spherical shape. Even assuming true circular motion, constant pressure, and uniform hardness of the rock, the question still arises: how does one maintain a spherical shape as the depth of the hole increases.

Rubbing stones, known in Shona as ‘huyo’, still abound in Zimbabwe where elliptical grinding hollows are plentiful on dwalas, and around village sites where portable grinding stones were once used. At spherical rock-hole sites, however, we have not yet found a rubbing-stone which we can say with confidence was the tool used to make these holes. Should we ever find one then we may have the key to solving the mystery.

We have now visited fifteen sites in Zimbabwe and recorded over a hundred holes. They are not as numerous as other grinding hollows but we know they are not rare, as initially thought.

In 2002 I (Voytek) visited Bikita Mine, a lithium mine, where we had had a report of a group of rock-holes on a petalite outcrop – the first ones reported in rock other than granite. Unfort­un­ately, before I had a chance to see them, these holes were destroyed in exploratory blasts. I was lucky enough, however, to meet villagers who showed me other rock-holes in the area (in granite), which conform to the (spherical) shape we are studying.

The sites so far located and visited include Chegutu, Kwekwe, Naletale Ruins, Masvingo area, Bikita, Matopos, and south of West Nicholson. More recently we have located these specific rock-holes in Harare.

An interesting feature pertaining to distribution is that the size of the holes is similar in any one area but varies in size from site to site. Sizes range from 160mm spheres at Sondelani to over 300mm around Masvingo. The size refers to the diameter of a sphere that would fit the hollow, irrespective of how deep the hollow. (It is not the diameter of the plan view of the hollow.) Generally the depth was no more than a third of the radius of curvature of the sphere.

When viewing a site one naturally asks, “Why here?”

We have found nothing remarkable about any of the locations. The site isn’t a rocky amphitheatre, which might have been used for religious purposes; it isn’t on top of hills with commanding views; it isn’t adjacent to a river or watercourse, although water may not have been far away. We have not seen any evidence of ancient mining near these sites. We have not found any abandoned piles of mineral rocks or visible waste material of any kind, and we ourselves are not sufficiently knowledge­able to recognise the telltale vegetation of previously occupied areas. We presume there was a good reason for choosing that spot but, often to our eyes, there are better sites only a short distance away. We are clearly missing something.

Generally the location is not on the flat but rather on a gentle slope with perhaps a flattish patch on which to start the hollow. We have, however, found these rock-holes on large flat rocks and, once, in a portable stone.

Sondelani Ranch, south of West Nicholson, proved to be ideal for viewing these rock-holes as the sites vary considerably. We found holes in low flattish rocks, no more than 3m in breadth and 0,25m above the surrounding sparsely-grassed sandy plain; on rocky outcrops in woodland; on the lower slopes of a wide granite dwala, and, to our delight, fourteen holes dotted the length of a granite slope rising above a large baobab tree: the most rock-holes we have seen in any one place.

The furthest south we have located these rock-holes in Zimbabwe is at Sondelani about 150 km north of Beitbridge. No report of their existence south of our border or in neighbouring countries has yet been relayed to us, although it seems probable that eventually we will hear of a site south of the Limpopo as Zimbabwe culture was not confined to the present borders – in fact a current view is that the culture originated at Mapungubwe just south of the border at the junction of the Shashi and Limpopo Rivers.

Who made them and How?
To date, archaeologists – professional and amateur, for several reasons, have not recognized the uncanny precision of the spherical hollows. We believe we have stumbled on something that has been missed and is waiting to be researched: a subject that needs to be brought to the attention of both the scientific community and the general public. We want to know, for instance:
· Who were the people that created them?
· When did they create them?
· What was the activity – domestic: grinding foodstuffs, or mining: grinding minerals?
· How did they make them – how was the stone tool driven and guided to produce a spherical hollow? It is the GEOMETRY of the hollow that provides the greatest fascination.

Apart from answering these questions, we hope future research will determine a link between the spherical holes and at least one of the known cultures of Zimbabwe, as well as contribute to the knowledge of Zimbabwe's mysterious past.

As with the mystery of Great Zimbabwe, where there is a gap between that culture and the culture of the present occupiers of Zimbabwe, there is a similar gap in our subject. Research may reveal that somewhere in the oral tradition there may be reference to the activity connected with the spherical rock-holes, however, when talking to local elders on the origins of the rock-holes the responses were “They’ve always been here” or that “God made them”, which in effect means the same. This suggests that the people who practised the ‘Spherical Rock-hole Cultural Activity’ did not pass it on. There was a definite break between them and the people we now know as the Shona.

The tools and products of the people's activity are also gone, or lie hidden: only the holes remain. Our efforts, therefore, must be directed to evidence, however small, which they may still contain.

Today, we have an opportunity to study these rock-holes and can apply modern science to unlock the mysteries they contain. We can use Global Positioning Systems (GPS) to accurately locate sites; we can map scratch-marks with a digital microscope, analyse material trapped in minute cracks and crevices with, say, a mass-spectrometer, measure and analyse the hollow-shape using photogrammetry in conjunction with computer programs.

Some years ago we contacted the Department of GeoInformatics at the University of Zimbabwe with a view to doing photogrammetry locally. They took various photographs and we hoped for great things. However, they appear to be under-funded and the project never took off.

Photogrammetry is relatively easy to do by organisations with the necessary staff and equipment, and we believe the information produced would be most useful in this project. We would welcome contact from any institution willing to assist.

We have listed the mysteries and posed some questions. What are our conclusions?
1) The spherical rock-holes were made by indigenous people who lived here at that time – whoever, whenever.
2) The activity was most likely the grinding of foodstuffs. For a variety of reasons it was unlikely to have been the grinding of minerals.
3) The grinding hollows are numerous and widespread in Zimbabwe.
4) The technology was simple and it was easy to do.

“Is that all you know after ten years of investigation?” we hear you ask. Well . . . yes, that is the way with mysteries.

We hope that this article will stimulate interest and discussion, and maybe lead to feedback on the sites within Zimbabwe and in adjoining countries. We believe the subject is fascinating, requires further research, and is a suitable subject for a post-graduate thesis.

We can be contacted on email: < >

Mr W. Popiel (Voytek)
6 Faversham Close
Harare, Zimbabwe
Tel: 263 - (0)4 - 33 67 86

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