Wednesday, June 18, 2014

0256 - The origin of walled enclosures in Alentejo

Radiocarbon dates for walled enclosures in Alentejo

For some time the origin of walled enclosures in Alentejo was thought to have occurred in the second half of the 4th millennium BC. The radiocarbon dates from two sites seem to indicate so: the chronologies from Monte da Tumba (Silva e Sores, 1987) and São Brás (Parreira, 1983).

These old dates, thought, were obtained over charcoal and they have a large standard deviation and in face of another set of dates, some of them more recent and obtained over bone, the actual image on the issue has changed.

The dates from Escoural (Gomes, 1991) walled enclosure, from Monte Novo dos Albardeiros (Gonçalves, 1988/89) and more recently from São Pedro (Mataloto, 2010) and  Porto das Carretas (Soares e Silva, 2010) indicate that these architectures emerge in the beginning of the 3rd millennium BC, namely after 2900 BC. This is coincident with the limit that radiocarbon establishes between Late Neolithic and Chalcolithic contexts in ditched enclosures (Valera, 2013a). Furthermore, the chronology available for the Late Neolithic hypogea of Sobreira de Cima (Valera, 2013b) and for the funerary context of Gruta do Escoural (Araújo e Lejeune, 1995), clearly in the second half of the 4th, corroborates this argument. In fact, it is not credible that these funerary contexts, with their unquestionable Neolithic assemblages, could be contemporaneous of early Chalcolithic walled enclosures, with a completely different material assemblage and just a few miles away.

The old dates should be abandoned in the debate of the origin of the walled enclosures in Alentejo. They clearly are a phenomena of the beginning of the 3rd millennium BC. And an ephemeral one, since the majority of the dated ones seem to end around the middle of the millennium (the recent dates of Porto das Carretas correspond to a phase where the enclosure was already deactivated and the one from M.N. dos Albardeiros from a possible reutilization). Several are reoccupied in Beaker times, but not as enclosures, like Porto das Carretas or Mnte do Tosco (Valera, 2000).

In the long time span of ditched enclosures, walled enclosures could have been just a temporary adding to the architectures of the societies that lived in the region.

This is an argument that I am developing in a paper that is almost ready.

Thursday, June 12, 2014

0255 - Evaluating the effort 3

Prehistoric ditch in Avebury (UK)

Evaluating the effort of digging ditches and of building ditched enclosures is not just a question of measure the amount of rock and earth excavated and moved. That is just part of the equation. Other important parts are the number of people involved and the duration of the building activities. As noticed by me and others, great building enterprises are available to small communities if they are done by stages in time and if they can congregate the will of the community. And it is in that will that I want to focus today.

Functionalist approaches naturally focus on function. No problem with that. The thing is that they focus in the function of the structure once it is built, and pay no attention to the function of the building process, which is an important social one.

For some decades now, some have argued for the need to focus on the social importance of the act of building. An act that goes much further than the pretended function of the feature itself. We have innumerous examples from all over the world and from different historical periods. Let me just give one example that I think is known to everyone: when Amish are reunited to build a barn for one member of the community, they are not simply building a barn to perform the function of storing the crops. They are doing something that touches deeply the identity of the community and reinforces their world vision, their social, political and religious bonds. As Marcel Mauss reminds us in his essay about the gift in polonaise societies, this facts that we study (in this case building activities) “are all total social facts, for they put in movement the totality of the society and its institutions or just an enormous number of those institutions, in particular when interactions were related to individuals. All these phenomena are simultaneously juridical, economical, religious, esthetical, morphological, etc.”

That is why some decades ago Evens argued that the process of building an enclosure had its main focus on the build process. For a functionalist mind focus on the subsequent utility of the thing, this might be hard to understand. But in many societies, inclusive in ours, many creations culminates in the very act of creation. Christ, we are leaving the times of the ephemeral.

And yet, it seems so difficult for some, today, to conceive that huge building enterprises might have had their basic motivations in the very act of building, in an ephemeral use and in the subsequent condemnation and in its social and ideological implications.

To evaluate the effort of building ditched enclosures in Prehistory it is important to go further than impressive metrics and politics of coercion.

Sunday, June 8, 2014

0254 – Knowing what method to choose

At Perdigões two methods of geophysics were tested. First georadar. Slower and needing a considerable cleaned soil (for the radar runs a few inches over the surface), this method was totally disappointing. 

Georadar image of the center of Perdigões enclosures

On the contrary, magnetometry, not just is faster in the measurements, but provided excellent results. In Perdigões, but also in Xancra, Moreiros 2, Monte do Olival 1, Luz 20, Montoito, Monte da Contenda, images that you can see all through this blog. Or you can search in the net for tens of European examples.

Image of the same area done by magnetometry 

For negative structures, like pits and ditches, magnetometry is the method that provides best results. Of course the quality depends of several circumstances (like the bedrock or the proximity of highly magnetic material) that need to be taken into consideration.  But the results leave no doubt.

Friday, June 6, 2014

0253 – Evaluating the effort 2

At Perdigões we have recorded 12 ditches. Seven of them were already surveyed in a section. Of course that we do not know if the dimensions of those sections “speak” for the entire perimeter of the ditches. We have evidence from other sites that a ditch volume and shape may change a lot along its perimeter. And Perdigões is not an exception. Ditch 12, the only one surveyed in two different areas, has a different shape and a different filling in survey 1 of Sector Q and in survey 2 of the same sector.

That shows us that we cannot generalize to a whole ditch what we observe in one section. But does not imply that, in general terms, we cannot try to approach the general picture.

For instance, Dicth 1 at Perdigões is a long one: it has a perimeter of almost 1,5 km. It was surveyed in a section near Gate 1, first by the ERA team and in the last few years by University of Málaga team (that is collaboration in the General Program of Research of Perdigões). It showed a “V” shape, with about 3 m deep and 7 to 9 meters wide. It allow us to calculate a volume for a one meter section: 9.61 m3. Multiplying this volume by the perimeter we get a volume of 14232 m3 and using the pattern wait of a m3 of diorite (around 2600 Kg) we have 37 000 tons of rock extracted, just for Ditch 1.

This can gives us an idea of the amount of work involved in Perdigões through its living time. And more interesting: once again, where is that amount of bedrock?

Ah! And do not forget that we have evidences of practices of re-cutting of some ditches after their first filling process. And that enlarges the amount of work that we can calculate to the recorded structures.

These big enclosures were huge public enterprises.